Additives are chemicals that can be added to fuels and are used to enhance certain performance characteristics. Some are designed to help eliminate carbon build-up inside the engine. There are also additives that are used to improve the lubricant properties of new low sulfur diesel fuels for example.

Additives are chemicals that can be added to fuels and are used to enhance certain performance characteristics. The quality of the fuel available to consumers can vary significantly. Many fuel companies add detergents to their fuel to meet a minimum requirement by law however it is often not enough.  New low sulfur diesel fuel no longer has the lubrication properties it once had and an additive is needed to restore it.

How do deposits affect my engine?

Deposits at the tip can impact fuel flow, upsetting the air/fuel mixture.

Diesel fuel is a highly complex fuel. It changes chemical structure during the time after it leaves the refinery to the time it is pumped into holding tanks and into the fuel station to the time it gets pumped into your vehicle. Fuel molecules oxidize and change structure and the energy per unit volume of the fuel can change during this process, which can negatively affect the performance of your engine. By using the proper type and ratio of fuel additives you can effectively combat the effects of fuel degradation and increase the Cetane value of the fuel and allows the engine to extract more power from a gallon of fuel, plus numerous other benefits.

Diesel fuel contains more energy per gallon than gasoline. The three types of diesel fuel are 1D, 2D and a blend of the two used during the winter.  1D is a lighter grade of fuel and provides less energy than 2D. Generally 1D can be used to reduce/eliminate fuel gelling in cold winter climates or it can be mixed with 2D.

The ignition quality of diesel fuel is measured by its Cetane rating. The higher the Cetane level the easier the fuel burns evenly and the produces power. Average diesel fuel is approximately a 40 Cetane level. Generally 45-50 ranges is considered premium diesel. However, just because a diesel fuel pump says “premium” on it does not necessarily mean that the Cetane level is between 45-50 since different states and countries have different regulations addressing what constitutes a premium diesel fuel.

Check with the particular fuel station as to exactly what Cetane levels the fuel is they are selling, or if you use the station regularly have the fuel tested to be assured of quality fuel. Higher Cetane numbers produce improved derivability, reduced emissions and black smoke and the driver of the vehicle or owner of a generator in our case can see and feel the difference in power that a higher
Cetane number produces.

The generator’s fuel pump is a plunger type. They are moved by a lobe on the cam shaft that pushes on the fuel pump plunger to generate a precisely metered high-pressure pulse of fuel to the injectors.

Excess fuel at the injector is returned to the fuel thank by a “spill return” fuel line.

The Fuel injectors job it  to atomize the fuel through pumping it into small nozzle under a very high pressure. The opening of the fuel injector where the fuel passes are smaller then a grain of sand.  Any deposits or damage to them results in either blockage or an uneven spray pattern.  The end result is poor combustion and lack of power.

A worn injector can also leak and drip fuel when it is not needed resulting in unburned fuel being sent to the exhaust where it can collect and plug up the injector.   Often overheating of the exhaust may be from damaged fuel injectors that leak or drop fuel.

It is very important to keep the fuel clean and free from contamination.

It is recommended with the new low sulfur fuels to use a fuel additive that will help insure your fuel pump and injectors remain lubricated and clean at all times.

There are many technical reasons why to chose diesel over gasoline however the point of this document is to help identify some important things necessary to truly benefit from diesel and insure your generator continues to run long after its equivalent gasoline generator has died.

Diesel engines operate at twice the compression ratio of gasoline engines; create greater internal pressures and heat. Components are made to closer tolerances, therefore are more easily damaged by dirt, corrosion improper fuel and lubricants. The key to getting extended life out of a diesel engine is its fuel and oil.

Diesel injectors are expensive precision parts that handle fuel pressures as high as 137,900 kPa. Using correct diesel fuel is essential because it not only runs the engine, but also lubricates and cools the fuel pump, injectors and spray tip.

Dripping or leaking injectors can cause rough engine operation, destructive unbalanced cylinder temperatures, crankcase oil dilution and incomplete combustion. Because of diesel fuel’s acid content, combustion byproducts are more corrosive. Greater diesel heat also converts combustion by products to varnish inside the engine more rapidly.

Dirt and water bypassing fuel filters can badly score fuel pump and injectors, requiring replacement. Rust can cause sticking in pump pressure regulator valves. Water in fuel can also cause hard starting, uneven running and frequent stalling.

Because diesel engines breathe more air per hour than gasoline engines, air leaks through cracks, loose connections or holes in flexible hoses can cause serious and expensive engine damage. Clogged air filters reduce power.

Diesel engines make more use of oil as a coolant because of greater heat and pressure. For example, the oil cools piston undersides. Improperly or inadequately filtered oil can cause scoring and damaging of engine parts. Inadequate circulation of oil and coolant can cause engine overheating and thermal distortion.

Poor quality fuel can cause hard starting, incomplete combustion with varnish buildup, smoky exhaust, and plugged fuel filters in cold weather.

Don’t let the above scare you, there is a far greater list for the problems you can and often will encounter with a gasoline engine. Remember most of this is for information purposes and to help you get the maximum life out of a diesel generator.

There are many technical reasons why to chose diesel over gasoline however the point of this document is to help identify some important things necessary to truly benefit from diesel and insure your generator continues to run long after its equivalent gasoline generator has died.

Diesel engines operate at twice the compression ratio of gasoline engines; create greater internal pressures and heat. Components are made to closer tolerances, therefore are more easily damaged by dirt, corrosion improper fuel and lubricants. The key to getting extended life out of a diesel engine is its fuel and oil.

Diesel injectors are expensive precision parts that handle fuel pressures as high as 137,900 kPa. Using correct diesel fuel is essential because it not only runs the engine, but also lubricates and cools the fuel pump, injectors and spray tip.

Dripping or leaking injectors can cause rough engine operation, destructive unbalanced cylinder temperatures, crankcase oil dilution and incomplete combustion. Because of diesel fuel’s acid content, combustion byproducts are more corrosive. Greater diesel heat also converts combustion by products to varnish inside the engine more rapidly.

Dirt and water bypassing fuel filters can badly score fuel pump and injectors, requiring replacement. Rust can cause sticking in pump pressure regulator valves. Water in fuel can also cause hard starting, uneven running and frequent stalling.

Because diesel engines breathe more air per hour than gasoline engines, air leaks through cracks, loose connections or holes in flexible hoses can cause serious and expensive engine damage. Clogged air filters reduce power.

Diesel engines make more use of oil as a coolant because of greater heat and pressure. For example, the oil cools piston undersides. Improperly or inadequately filtered oil can cause scoring and damaging of engine parts. Inadequate circulation of oil and coolant can cause engine overheating and thermal distortion.

Poor quality fuel can cause hard starting, incomplete combustion with varnish buildup, smoky exhaust, and plugged fuel filters in cold weather.

Don’t let the above scare you, there is a far greater list for the problems you can and often will encounter with a gasoline engine. Remember most of this is for information purposes and to help you get the maximum life out of a diesel generator.

Generator batteries are sometimes sealed and maintenance free.

Lead Acid batteries are often used however because the content is an acid it is considered a hazardous material and often can not be shipped.

If your generator comes with a dry battery then you may be required to get it filled at Napa Auto Parts for example. The charge is minimal.

Most generators sold here come with sealed maintenance free batteries and do not need to be filled.

How the battery works.

A lead-acid battery is composed of a series of plates immerse in a solution of sulfuric acid. Each plate consists of a grid upon which is attached the active material (lead dioxide on the negative plates, pure lead on the positive plates.) All of the negative plates are connected together, as are all of the positive plates.

When the battery is under load and being discharged, acid from the electrolyte combines with the active plate material. This releases energy and converts the plate material to lead sulfate. The electrolyte become less acidic in the process.

When a battery is recharged, the opposite occurs: the lead sulfate reverts back to active material, and the electrolyte becomes more acidic with a higher specific gravity.

Battery Charging

To recharge a lead-acid battery, it is necessary to convert the lead sulfate material which attaches to the discharged areas of the plates back to active plate material.

If the battery has not remained discharged for long or has only been discharged slightly, this is a relatively easy process. However, when the battery has remained discharged for an extended period or has been subjected to repeated deep-discharges without charging fully between cycles, the sulfate material can harden into crystals which are more difficult to convert. Until the sulfate is converted, the sulfated portions of the plates are useless, and the battery can accept and hold only a partial charge. Eventually, sulfating can ruin a battery.

Sulfation is the number one cause of battery failure.

Whenever possible, bring any batteries up to full charge as slowly as possible. This slow charging process is also known as equalization. Equalization allows the electrolyte time to diffuse into the less accessible areas of the plate grid and convert those areas from lead sulfate to active plate material.

Infrequently-used or stored batteries are also prone to sulfating if not kept fully-charged between uses. A battery loses approximately 1 percent of its charge per day (up to 2 percent in hotter climates) due to self-discharge. If self-discharge is not compensated for, a stored battery can become sulfated and will eventually be ruined.

The second most common cause of battery failure is overcharging. Many chargers on the market will damage your battery if left attached for extended periods by “boiling” the water out of the electrolyte solution. Eventually, water loss will destroy a battery. Checking the electrolyte level in a battery and adding distilled water when necessary is extremely important, especially when using fast chargers or many of the trickle chargers on the market.

Buy a small trickle charger and leave it on full time or hook up a small solar cell to keep the battery topped up when not in use.

Diesel fuel is principally a blend of petroleum-derived compounds called middle distillates (heavier than gasoline but lighter than lube oil) and may or may not contain additional additives. Other middle distillates include kerosene and No. 2 Heating Oil. Diesel fuel is designed to operate in a diesel engine where it is injected into the compressed, high-temperature air in the combustion chamber and ignites spontaneously. This differs from gasoline, which is ignited in a gasoline engine by the spark plugs.

Why are diesel engines so popular?

Diesels engines deliver 20% to 40% better fuel economy than gasoline engines. Diesel fuel does not require as much refining. The engines are simple and easy to maintain. There is no spark plug, ignition cables, carburetors and complicated fuel control devices. Diesel fuel has less harmful emissions from diesel fuel than gasoline. Now with new ultra low sulphur diesel fuel the benefits to the environment are huge.

Winter and Summer Diesel

In order to keep diesel fuel low temperature flow characteristics, fuel suppliers adjust the fuel properties through the year according to historical temperature data and where the fuel is sold. Generator owners may have fuel sitting in their tanks or in storage for long periods of time. In cold weather it would be advisable to add a fuel anti-gel additive. Anti-Gel treatment may be conveniently poured into the fuel tank before filling. It is inexpensive and worth spending the time to do it. More on this later.

Diesel Smoke

When a cold diesel engine is started, the walls of the combustion chamber are still cold. The low temperature in the combustion chamber results in incomplete combustion, and the white smoke.

Even after the engine has started, the temperatures in the combustion chamber may still be too low to induce complete combustion of the injected fuel. The resulting unburned and partially burned fuel is exhausted as a mist of small droplets that is seen as white smoke (cold smoke). This situation normally lasts for less than a minute, but the exhaust is irritating to the eyes. A fuel with a higher cetane number will shorten the time during which unburned fuel is emitted to the atmosphere.

Cetane

Cetane is to diesel engines as octane is to gasoline engines. The Cetane Number is a measure of how readily the fuel starts to burn (auto-ignites) under diesel engine conditions. A fuel with a high cetane number starts to burn shortly after it is injected into the cylinder; it has a short ignition delay period. Conversely, a fuel with a low cetane number resists auto-ignition and has a longer ignition delay period.
What makes A Diesel Engine Noisy?

The noise produced by a diesel engine is a combination of combustion noise and mechanical noise. Fuel properties can affect only combustion noise. Some combustion noise is reduced in generators by using direct injection. A good muffler system can reduce a great deal of noise. Increasing the cetane number of the fuel can decrease the amount of knock also.

Low-Sulfur Diesel Fuel

Ultra-low sulfur diesel (ULSD) began replacing conventional diesel fuel in 2006. The new fuel will contain 97% less sulfur than conventional diesel—sulfur will be reduced from 500 parts per million (ppm) to 15 ppm.

There are many ways of removing the sulfur content. The cheapest of these involves hydrotreating, a process that removes sulphur by treating it with hydrogen. Unfortunately, hydrogen is highly reactive and also reduces the lubricity, or lubrication properties, of the end-product diesel.

Since the removal of sulfur from diesel fuel, diesel shops have been flooded with work caused by lack of lubrication in the new fuels. Cars, Trucks and Generators can all see the effects of this. Fuel Injector and Fuel pump failure can be common since they are not lubricated like they where before. Some fuel companies have their own additives in the fuel to bring back the lubricaton properties however it may not be enough.

Leading diesel manufactures now recommend using a fuel additive such as Stantadyne with every fill up to restore the lost properties.

Additives are cheap and easy to use. Check your gas station or automotive parts dealers. They are as common as windshield washer fluid where diesel products are sold.

In your Diesel Generator the only lubrication your fuel valve, fuel pump and fuel injector receives is from the fuel itself. Since failure of these components are not covered by any warranty it is important to take care of them. Taking care of them is easy if you use a fuel additive that restores or improves lubrication and antioxidant properties to your fuel.

• Stanadyne White Paper on Diesel Fuel
• How Stuff Works The difference between gasoline, kerosene, diesel fuel, etc.
• Vegetable Oil is Used as Fuel
• FAQ Exxon Diesel Fuel

Fuel Injectors

Most diesel engine problems are related to the fuel system. The fuel injectors and fuel pumps must be lubricated and kept deposit free. Since Sulfur has been removed from most fuels now, a fuel system additive that helps clean and lubricate the fuel system is required. You should use the additive with every fill up. Failure to use it will result in unusual wear and tear that will not be covered under warranty.

How the fuel is delivered is the most common reason for engine failure. Often looking at the color of the smoke will tell you a lot about what is going on.

Black Smoke

Excessive diesel smoke is due to incomplete combustion, a rich air-fuel mixture. This may be the result of problems with the fuel injector pump or its timing. It may be a clue that the air cleaner is choked. Worn or damaged fuel injectors and adulterated diesel fuel can also cause this.

Sometimes when a fuel injector fails it can leak fuel and drip. The excess fuel does not burn off and is pushed out into the exhaust where it can collect, burn and overheat the system. Often deposits left there will also glow cherry red and burn off. Black smoke is an indication that fuel is not burning properly.

White Smoke

White smoke occurs mainly during cold starts, when the fuel tends to condense into liquid and does not burn due to cold engine parts. The most common reason for white smoke are in-operative glow plugs, low engine compression, a bad injector spray pattern, late injection timing or injection pump problems.

Blue Smoke

Excessive blue smoke indicates problems from low engine compression and/or worn piston rings, scored cylinder walls or leaking valve stem seals The blue smoke is caused by crankcase oil entering the combustion chamber and being emitted after partial combustion through the exhaust

Diesel Fuel in cold weather.

Below 15 degrees F, wax crystals begin to form in diesel fuel. These will clog the fuel filter and stop the engine as the temperature drops toward 0 F. Any good “winter fuel conditioner” for diesel fuel will keep the fuel moving to at least -20 degrees. Follow the instructions on the bottle!

Here is an example of oil waxing in cold weather. On the right is oil treated with an anti gelling additive.

Deposits and Corrosion

Residual carbon deposits from combustion can build up in nozzles and around the orifices and can obstruct the atomization of the fuel into the air preventing complete combustion. Deposit modifiers and detergents soften the hard deposits allowing for their removal. The detergent will clean the soft deposits and prevent additional deposit build-up. Also, they incorporate an anti-oxidant, which helps fuel maintain its potency and a corrosion inhibitor to help protect fuel injection parts from rust and

Learn more about diesel fuel additives from

• AMSoil
• EPA and Diesel

Friction causes heat and until the break in occurs extra heat and most of the wear and tear will happen during this period. Break in your engine before using it! Don’t forget oil will become contaminated faster because of combustion blow by fumes and metal that is ground away during the mating process. The oil should be changed at at the first 25 hours.

This is an important time for an engine. You should not subject the engine to significant loading for the first 25 hours or more however some load IS desirable since the heat and friction is also needed for the break in to occur. Excessive heat will burn oil and cause it to harden leaving an enamel like residue on the cylinder wall, commonly known as oil glazing and prevents the mating from occurring so small gaps between rings and cylinder surfaces will never seal. The same applies to use synthetic oil during the breakin period. It will also prevent break in from happening. Only use synthetic oil after the break in period.

A moderate loading is the key to a proper break in. 1/2 the rated power may be ideal. While some manuals suggest decreasing the RPM it is not easy to do on generator motors since they have a fixed run or stop position that locks into place on the throttle. If you can, secure it for this process for a break in period so are running it at half the RPM you will benefit from it in the long run. Obviously you can not use the generator until the normal speed is restored.

If you are thinking of using a generator above 3000 feet, don’t pick diesel or you will have problems.

To compensate for high altitude, engines need to be adjusted to avoid too rich a fuel/air mixture. Diesel engines are adjusted for high altitude by advancing the fuel injection timing. This gives the engine more time to burn the fuel before it is expelled. At high altitude engines are noisier, have difficulty accelerating and have reduced power output. Also, the rich mixture can generate black smoke, which indicates incomplete combustion or in extreme cases white smoke, caused by raw fuel in the exhaust.

Removing a shim between the engine and the fuel injection pump will advance the timing.

Once an engine has been adjusted for altitude it can overheat due to the lean mixture if operated at low altitude. There may be no other signs before engine damage occurs.

Some diesel engine manufactures such as Yanmar Diesel suggest the modifications be done at 5000 feet.

Manufactures normally setup their generators to run at at 500 ft If you intend to run a generator at higher altitudes you should let your dealer know this before you purchase a diesel generator.

Diesel engines can suffer damage as a result of mis-application or mis use – namely internal glazing and carbon buildup. This is a common problem in generator sets caused by failure to follow application and operating guidelines – ideally diesel engines should run at least around 60-75% of their maximum rated load. Short periods of low load running are permissible providing the set is brought up to full load, or close to full load on a regular basis.

Internal glazing and carbon buildup is due to prolonged periods of running at low speeds and/or low loads. Such conditions may occur when an engine is left idling as a ‘standby’ generating unit, ready to run up when needed, (mis use); if the engine powering the set is over-powered (mis application) for the load applied to it, causing the diesel unit to be under-loaded, or as is very often the case, when sets are started and run off load as a test (mis use).

Running an engine under low loads causes low cylinder pressures and consequent poor piston ring sealing since this relies on the gas pressure to force them against the oil film on the bores to form the seal. Low cylinder pressures causes poor combustion and resultant low combustion pressures and temperatures.

This poor combustion leads to soot formation and unburnt fuel residues which clogs and gums piston rings. This causes a further drop in sealing efficiency and exacerbates the initial low pressure. Glazing occurs when hot combustion gases blow past the now poorly-sealing piston rings, causing the lubricating oil on the cylinder walls to ‘flash burn’, creating an enamel-like glaze which smooths the bore and removes the effect of the intricate pattern of honing marks machined into the bore surface. which are there to hold oil and return it to the crankcase via the scraper ring.

Hard carbon also forms from poor combustion and this is highly abrasive and scrapes the honing marks on the bores leading to bore polishing, which then leads to increased oil consumption (blue smoking) and yet further loss of pressure, since the oil film trapped in the honing marks is intended to maintain the piston seal and pressures.

Un-burnt fuel leaks past the piston rings and contaminates the lubricating oil. Poor combustion causes the injectors to become clogged with soot, causing further deterioration in combustion and black smoking.

The problem is increased further the formation of acids in the engine oil caused by condensed water and combustion by-products which would normally boil off at higher temperatures. This acidic build-up in the lubricating oil causes slow but ultimately damaging wear to bearing surfaces.

This cycle of degradation means that the engine soon becomes irreversibly damaged and may not start at all and will no longer be able to reach full power when required.

Under loaded running inevitably causes not only white smoke from unburnt fuel but over time is joined by the blue smoke of burnt lubricating oil leaking past the damaged piston rings, and the black smoke caused by the damaged injectors. This pollution is unacceptable to the authorities and any neighbours.

Once glazing or carbon build up has occurred, it can only be cured by stripping down the engine and re-boring the cylinder bores, machining new honing marks and stripping, cleaning and de-coking combustion chambers, fuel injector nozzles and valves. If detected in the early stages, running an engine at maximum load to raise the internal pressures and temperatures, allows the piston rings to scrape glaze off the bores and allow carbon buildup to be burnt off. However, if glazing has progressed to the stage where the piston rings have seized into their grooves this will not have any effect.

The situation can be prevented by carefully selecting the generator set in accordance with manufacturers printed guidelines.

For emergency only sets, which are islanded, the emergency load is often only about 1/4 of the sets standby rating, this apparent over size being necessitated to be able to meet starting loads and minimising starting voltage drop. Hence the available load is not usually enough for load testing and again engine damage will result if this us used as the weekly or monthly load test. This situation can be dealt with by hiring in a load bank for regular testing, or installing a permanent load bank. Both these options cost money in terms of engine wear and fuel use but are better than the alternative of under loading the engine. For remote locations a Salt water rheostat can be readilly constructed.

Often the best solution in these cases will be to convert the set to parallel running and feed power into the grid, if available, once a month on load test, and or enrolling the set in utility Reserve Service type schemes, thereby gaining revenue from the fuel burnt

Effects of Water on Diesel Fuel & Oil

Premature engine ware including pitting of bearings is a indication of water contamination. The water has two effects; it causes corrosion of the surfaces, and it also disrupts or degrades the mechanism of lubrication. Rolling bearing lubrication is by elastohydrodynamic action (EHL or EHD lubrication), and the presence of water tends to inhibit the formation of the EHL film. Even 0.1% of water has a significant effect, and 1% water can reduce bearing life by a factor of 10.

BioDiesel & Contamination By Water

Biodiesel may contain small but problematic quantities of water. Although it is not miscible with water, it is, like ethanol, hygroscopic (absorbs water from atmospheric moisture). One of the reasons biodiesel can absorb water is the persistence of mono and diglycerides left over from an incomplete reaction. These molecules can act as an emulsifier, allowing water to mix with the biodiesel. In addition, there may be water that is residual to processing or resulting from storage tank condensation. The presence of water is a problem because:

• Water reduces the heat of combustion of the bulk fuel. This means more smoke, harder starting, less power.
• Water causes corrosion of vital fuel system components: fuel pumps, injector pumps, fuel lines, etc.
• Water & microbes cause the paper element filters in the system to fail (rot), which in turn results in premature failure of the fuel pump due to ingestion of large particles.
• Water freezes to form ice crystals near 0C (32F). These crystals provide sites for nucleation and accelerate the gelling of the residual fuel.
• Water accelerates the growth of microbe colonies, which can plug up a fuel system. Biodiesel users who have heated fuel tanks therefore face a year-round microbe problem.
• Additionally, water can cause pitting in the pistons on a diesel engine.

Before you start troubleshooting.

Safety is the primary concern in troubleshooting generators. If you are not sure of what your doing ask or leave it to a professional. Understand what you are doing and use caution. There is a risk of injury from moving parts, heat and live electrical wires that can shock and kill you.

The first step in generator troubleshooting is to conduct a visual inspection before doing any electrical tests. Looking the generator over carefully should expose any environmental factors that might contribute to the problem. As you remove the generator cover and begin your inspection, look for the following:

• Rusted or corroded connections. An oxidized connection will prevent the circuit from being completed. This applies not only to the major cables externally, but also to the electronic control devices internally.
• Signs of overheating. Discoloration and or burnt smells. Windings that are normally copper in color that may have turned black. The insulating sprays that manufacturers use to insulate the windings may vary in color from shades of reddish brown to light brown to dark brown, so try to compare the color to that of a new unit.
• Wire insulation that is heat-hardened. Fabric and plastic insulation hardens over time due to heat exposure and overheating. Long-term heating should be more uniform. A short, excessive heat cycle may have less hardening and burning at the unit’s outer perimeters and excessive heat signs toward the center or heat source.
• Insects that have developed a community inside the generator. Their nests and debris can cause electrical shorts. Generators left out in the elements, such as for running water wells, provide a nice home for critters such as spiders, wasps, and mice.
• Loose bolts, screws, and fasteners. This condition will either prevent full-time service or give intermittent service depending on the situation.

Engine Will Not Start

A diesel mechanic will often find a failure in a diesel engine to be a direct result of something the user did or failed to do rather then a manufacturing defect or product quality. Warranties only cover manufacturing defects and not failure due to neglect or abuse. Trying to fix a problem yourself is often the best first step. To do the work yourself you need to understand some basic stuff that we will cover here.

When a diesel engine stops running or fails to start, the most common cause is a fuel problem. Checking the fuel system is your first step.

Your diesel generator is designed to work with normal automotive diesel fuel. Using anything else will leave evidence it behind. In warranty claims manufactures and dealers have tests to check for traces of wrong fuel used and look for deposits in the combustion chamber and fuel system to void a warranty. If you use the fuel it was designed to use then this will never be an issue.

Here is how the fuel system works. Fuel from the tank flows by gravity through a fuel filter. The filter may be inside the tank or mounted outside. The fuel filter housing often has a turn off valve on it. Next the fuel goes to the pump where it is pumped under very high pressure to the fuel injector. The amount of fuel pumped is controlled by the throttle position, the connection is internal and it adjusts the fuel pump volume. This effects the engine speed. The throttle position is also fine tuned by a engine speed governor to control the engine speed. Many fuel pumps now have a electric valve on them to also turn off the fuel and cause the engine to shut down if needed. Some will just release the throttle to do the same thing.

How to check the fuel system

Make sure you are using ONLY normal automotive diesel fuel you purchase from a gas station. Do not use furnace oil, red dye fuel or anything else. In the winter time fuel that is very cold will gell. Fuel that gells will break apart and will also clog filters and fuel lines.

Check fuel shut off valves under the fuel tank and on the inline fuel filter. If you are not sure if they are open then remove the rubber fuel line from the fuel pump and see if fuel flows out feely.

Anytime you run out of fuel it will cause air to reach the fuel pump and stall the engine. Even if you refill the tank air is still trapped in there and the pump will not work. Often it can not pass air because the air will compress where the fuel does not and it passes just fine. Trying to pass air through the pump will damage it and may also damage the fuel injector. You must remove the air by removing the rubber fuel line off the fuel pump and let the fuel run out until all air is removed. Do not crank the engine trying to remove the air or you will damage the fuel pump and or the fuel injector.

Air in the fuel can also be a cause of hard starting or a no start condition. Air can make the engine die after it starts, and make restarting difficult. Air can enter the system through any break in the fuel line or via a bleedback condition.

The best way to check if the fuel pump is working is to remove the fuel injector and with the fuel line connected and snug, fuel should spray out in 4 directions when cranking. (It is under high pressure, keep eyes protected and fingers away from the tip) Before you do it, make sure the throttle is in the run position. Check for any springs that may have come off the throttle assembly while your at it. You can also bleed any remaining air out by lessening the high pressure fuel line at the injector and cracking then replace it once there is a steady trickle of fuel coming out when you crank the engine.

Some fuel problems are a result of the electric fuel valve and that it has failed. It can get stuck from deposits in the fuel or even a grain of sand. The fuel valve can easily be removed and cleaned to fix the problem. When it fails to open fuel does not get into the fuel pump. Remove it, take out the plunger and spring and replace it. See if the fuel pump works again and you can start your generator.

The electric fuel valve is used to turn off the fuel supply and stop the engine if there is low oil pressue, you turn off the key switch or press off on the remote control. If it does not work and you disabled it then the only way to turn off the engine will be to release the throttle and or close some other fuel valve.

Compression is the second thing that is required for a diesel engine to work. Diesel motors work by compressing air so much and so fast that it creates a lot of heat. Enough heat and it will ignite the air and fuel mixture.

When cranking the engine and trying to start up it is important for the engine turns fast enough for enough compression to happen. Too slow cranking will not create enough heat to start the engine. Make sure your battery is fully charged and all connections are snug. If you can move any battery cable or wiring up to the starter then the connections are poor and it will result in slower cranking.

If you are at an altitude over 3000 feet then you will also have problems starting your engine. The air is too thin and there is not enough to compress and cause all the heat necessary for the engine to work. If you manage to get it started, you will not have complete combustion, black smoke will be visible because there is not enough heat to burn all the fuel completely. Further engine damage will occur.

Portable diesel engines use mechanical valve lifters and in the beginning they settle into place and ware down the most. You need to adjust the play between the rocker arm and the valve. If you do not then rather then it pushing the air intake and exhaust valves open they work like hammers and will quickly fail or there will be enough play that they will fall off. Checking it is easy. Remove the rocker cover and inspect it as shown below. Adjust it if necessary and look to see if the adjustment screw is broken off. This may happen if it was working like a hammer rather then pushing the valves as it should.

Fuel Delivery & Fuel Injectors

Fuel injectors require a high quality finely filtered diesel fuel to work.

Diesel injectors can suffer from the same kinds of ailments as gasoline injectors, including varnish deposits, clogging, wear and leakage. Today’s low sulfur diesel fuels are MORE likely to leave varnish and gum deposits on injectors, and also provide less lubrication so using a good fuel additive will help to keep things flowing smoothly.

When your fuel injectors get dirty or start leaking the result is often back smoke. You will notice a rough engine speed too. The dirty fuel injector can not create the fine spray needed to properly mix with the air and will not burn correctly as a result. But it is not always the problem. Black smoke is usually a signal that there’s too much fuel. Not having enough air will also cause this. Check that your air filter is not clogged and before changing your fuel injector check the valves. They should be adjusted first. When they are out of adjustment is will also result in not enough air exchange and incomplete combustion.

Here is how they work. Fuel is supplied from the fuel tank and is passed through a fuel filter system. This is the engines first and only line of defense, and it is the filters task to remove any sludge, sediment, rust or other contaminants that have found their way into the fuel tank. These types of systems are commonly fitted with 20-micron filters manufactured from tightly woven cellulose material. This filter is designed to mechanically prevent any abrasive material from entering the sensitive fuel injection system. A filter can only filter a set amount of sediment before blocking and becoming useless. Since most generators transfer fuel from the tank to the fuel pump by grafity, it does not take much to stop the normal flow of fuel.

Next a single feed then directs the diesel fuel into a high-pressure fuel pump. Here the fuel is pressurized and sent to the fuel injector nozzle in the engine cylinder. The pump is a plunger that is activated by a bump or lobe on the cam shaft that makes contact with it.

The amount of fuel the pump will pump is controlled by a metering valve. The amount of fuel changes the engine speed. The valve is part of the fuel pump. What you can see is the lever on the fuel pump as it moves to open and close the pump fuel flow. It looks like a arm with a pin on it. It fits into what looks like a fork arm that is connected to the throttle. One must fit inside the other for the throttle and governor to control the pump. If you take off the governor lever inspection cover then you can see it. You can move the throttle and see it move a lever on the fuel pump. If it is out of place then the engine speed will be erratic. It may have jumped out of place of you removed the fuel pump or have at any time forced put force on the throttle. It is a simple check to see see if it working correctly.

Back to the fuel pump pumping….. It is at this point that fuel quality plays a vital role. Diesel floods this mechanical device and all lubrication inside the fuel pump is now provided by the lubricating properties of the diesel fuel. Sediment in the fuel can act as a grinding paste, sulfur can mix with the water to form a mild sulfuric acid and cause chemical etching, water can cause rust and if the base fuel does not have enough lubricity some parts will simply cease. All this can cause catastrophic failure in the pump.

This pressurized fuel arrives at the injector nozzle. At a set pressure the needle within the injector will open and it will spray a set amount of diesel into the chamber. There are tiny holes at the tip of each injector nozzle that are designed to give an even spread of diesel fuel before it ignites.

Again the fuel quality is of utmost importance. If the viscosity of the diesel is perhaps to thick or to thin then the spray pattern will not be correct and the fuel will not atomize and achieve the correct combustion. Incomplete combustion can cause excessive exhaust smoke and carbon build up in the chamber and around the injector nozzle tips which could further alter the spray pattern or even block the tiny holes at the end of the injectors.

In cold weather fuel does not vaporize very well in the combustion chamber and this makes starting difficult.

Modern diesel engines designed for cold weather use a pre-heater or glow plugs. Glow plugs are heating elements that warm up the air that enters the engine. They work on a timed circuit or are manually activated just before the engine is started. The colder it gets, the longer those glow plugs need to stay on to preheat the combustion chamber for a smooth start.

Heating element found behind the air filter on some diesel generators

Using the decompression lever on a diesel engine will open up the exhaust valve and keep it open so you can crank faster. Seconds later you release the valve and the momentum of the engine often results in higher compression and speed necessary for starting under difficult conditions.

Decompression Leaver found on top of the motor

Gasoline engines that use a carburetor also suffer from difficult starting on cold weather. The cold air and cold cylinder walls prevent the fuel from vaporizing correctly to permit combustion.

Using Engine Starting Fluid is a very effective method to starting both gas and diesel engines in sub zero temperature.

Starting Fluids are made from Ether and petroleum distillates blended together. This starting fluid has a low freezing point and easily ignites even at temperatures as low as -65 F Many starting fluids have added lubricant and anti-corrosive additives. You can buy a spray-can of it at most gas stations and automotive stores. Use caution, it does not require much and over use in some cases may cause engine damage.

Diesel fuel thickens in cold weather. It has a tendency to gel. Diesel Fuel has some naturally occurring paraffin (wax) and as the temperature drops, this paraffin crystallizes and affects the fluidity of the fuel and may cause hard starting and eventually lead to filter plugging. You can use a fuel additive to prevent this and is recommended for all year round use.

Cold Weather – Batteries

Batteries that are weak may not crank the starter motor fast enough to start a cold engine. As the temperature goes down, so does battery capacity. A battery that has all of its power available at 80 degrees F will have only about 46% available power at 0 degrees F. Plus, the engine will be 2.5 times harder to start at 0 degrees due to thicker oil and resistance to movement of internal moving parts. In effect, an engine is about five times harder to start at 0 degrees F than at 80 degrees F. Test weak or suspicious batteries under load before cold weather to help eliminate potential problems during busy times. If batteries need replacement, always replace with a battery equal to or more powerful than the original battery.

Keep your battery stored indoors to prevent it from freezing. Consider buying a small battery charger / maintainer to keep the battery topped up so it is always ready to use.

Cold Weather – Oil

The warmer the engine oil is, the thinner it will be and have less resistance to moving engine parts. Make sure you are using the proper viscosity oil recommended for your engine for cold temperatures. If you cannot store engines inside or in a heated area, consider installing a block heater on the engine. To save time and electricity, put the block heater on an electrical timer set to come on a couple of hours before you plan to start the generator.

After starting the generator on a cold day, allow the engine to warm up a few minutes before putting it under load. Proper engine operation temperatures assure more efficient fuel combustion and may prevent damage to cold engine parts. Engine oil flows more readily at operating temperatures and allows proper lubrication of engine parts and areas.