If you work in fleet management or the construction sector, you almost certainly have diesel-powered equipment. Diesel is used in almost 75% of all heavy construction equipment, in addition to huge trucks. It has better fuel efficiency, reliability, power, and performance than gasoline, as well as lower carbon emissions.
When it comes to keeping these machines functioning, learning how to correctly repair your diesel fuel injection systems can save you time and money. Knowing what to look for and how to deal with them can help you avoid costly equipment breakdowns and machine downtime.
How do diesel fuel injectors work?
Pressurized diesel fuel is pumped via a fixed or electronically regulated aperture by diesel fuel injectors (opening). This method sprays or mists fuel into the engine, making it simpler to ignite than a heavy, solid stream. In addition, the mist burns more efficiently and uniformly.
When fuel injection systems aren't maintained properly, the procedure is ineffective and can potentially lead to a complete engine failure. Clogged/dirty fuel injectors and water or air in the fuel injection system are the most typical problems that impact diesel fuel injection systems.
To avoid injury, safety procedures should be performed before looking for or fixing these conditions.
Depressurize diesel fuel injection system before maintenance
When operating on a diesel system, extreme caution is required. Because diesel fuel operates at high pressures, it's critical to let your engine cool completely and depressurize the fuel injection system before doing any maintenance. When replacing the gasoline filter, this will protect you from dangerous fuel sprays.
To depressurize your fuel injection system:
- Shut off engine. Before starting work, always shut off your engine and allow it to cool completely.
- Loosen fuel filter cap. Slightly loosen the fuel filter cap without fully removing it — you will hear a hiss when cap is loosened.
- Locate and loosen fittings on fuel lines. Consult your owner’s manual to determine where your fuel lines are. In some vehicles, they are mounted on the undercarriage’s frame rail — while on others, they are in the engine compartment. Once you locate your fuel lines and fittings, turn a flare wrench counterclockwise to loosen (but not remove) the fittings.
- Wait for pressure to release. Wait several minutes for pressure to release. Clean up any spills while waiting.
- Remove fuel lines if replacing filters. If you are replacing your fuel filters, remove the fuel lines completely. If you are doing other work, simply leave them loosened until maintenance is completed.
Signs of clogged or dirty fuel injectors
Because diesel fuel is viscous, it holds dirt and debris in suspension better than gasoline. As a result, you should take every precaution to keep your injector systems and the gasoline itself clean. If the fuel injectors in a diesel engine are blocked or unclean, the diesel fuel may simply drip out rather than spraying a forceful, fine mist. Engines may skip or stop as a result of this.
Signs that you may have a clogged or dirty fuel injector include:
- Rough idling
- Hard starting
- Throttle hesitation
- Decreased fuel mileage
- Poor engine/machine performance
- Black smoke from the exhaust manifold
- Pinging sounds (officially referred to as pre-ignition)
It's also worth noting that clogged or dirty fuel injectors or injection system components might create the same issues as cracked or damaged ones. Maintaining and servicing your diesel engine on a regular basis is critical to keeping it running safely and efficiently.
Tips for keeping fuel injection systems clean include:
- Change oil regularly
- Replace filters
- Consider using high-quality additives aimed at protecting parts and keeping them clean (consult the manual or manufacturer for recommended additives for your machine).
Vehicle and machine models differ. You should consult your owner’s manual or manufacturer before performing work, but a few basic steps for changing diesel fuel filters include:
- Depressurize system as outlined above.
- Use your owner’s manual to locate the fuel filter (generally on the rear side of the engine)
- Find the sensors attached to the bottom of the fuel filter and remove the sensors’ wire plugs.
- Drain excess diesel by placing a pan under the fuel filter and opening the drain valve.
- Open the lid of the fuel filter can and use a fuel filter tool to unscrew the fuel filter — making sure to check for o-ring and bring can straight up without tilting (more fuel will drain into the pan as you perform this step).
- Lubricate new filter with diesel fuel and then place into fuel filter can — grease o-ring before placing it onto new filter.
- Put filter can back into position and close the drain valves — using fuel filter tool to tighten screws.
- Place wire plugs back onto sensors and follow bleeding procedures as outlined in your owner’s manual.
- When work is complete, turn engine on and check for any leakage.
Signs of water in fuel injection system
The presence of water in a gasoline system might cause the engine to miss or fully stop. When exposed to water, many modern fuel filters will automatically clog and cut off gasoline flow. Any water that enters the tank while fueling or forms as a result of condensation will most likely settle to the bottom and should be drained every day according to your machine's handbook.
Signs that you may have water in your fuel injection system may include:
- Pressure indicators showing varying degrees of pressure
- Engine missing or stopping entirely
- Fuel that appears dark and gummy — this is due to water mixing in with diesel fuel and causing microbe formation
- Sluggish performance
- Erratic idling
Tips for keeping water out of the diesel fuel injection system include:
- Drain it daily (if it’s an above-ground tank)
- Check for water — extract a small amount of diesel fuel using a hand-operated bilge pump into a transparent glass container. Check for discoloration. Water is heavier than diesel fuel and will settle to the bottom if it is present. You can also look for a thin, dark line between the water and fuel. This indicates that micro-organisms have developed, and a biocide should be added.
- Allow fuel to settle — before performing any maintenance, allow your fuel to settle in the tank — preferably for at least a full day.
- Bleed or pump water from tank
- Fill the tank at the end of each shift if possible
Hot fuel will be returned to the tank using high-pressure direct injection systems. Although most systems feature fuel coolers to minimise heat, the tanks are still above ambient temperatures and will hold more moisture than ambient air, resulting in a hot and humid atmosphere in the fuel tank.
When the tanks are allowed to cool overnight, moisture condenses, resulting in water in the gasoline. By refilling your tank at the conclusion of each shift, you'll be able to push out as much humid air as possible while also limiting the amount of water that can enter the system.
If your fuel is stored in a diesel-specific container, it should feature fuel-water separators and petcocks at the bottom. Many of them are see-through, allowing you to see when the water has been completely drained.
You can remove water from the actual fuel tank by utilising an extension line connected to the bilge pump to pump it out from the bottom.
To get rid of any microorganisms, apply a biocide to your fuel according to your owner's manual.
Signs of air in fuel injection system
If you've ever let your diesel machine run out of fuel, you know how difficult it can be to restart. This is due to the fact that too much air in your system prevents fuel from flowing properly and prevents fuel pumps from picking up and pushing diesel through the piping system. To discover how to correctly "bleed" air from your fuel system, consult your maintenance handbook.
The most common way to avoid this issue is to not let your machine run out of fuel in the first place. Steps for bleeding air from your fuel injection system include:
- Follow all instructions above and in your owner’s manual for allowing engine to cool and depressurize.
- Put enough diesel fuel in your tank to fill higher than the fuel filter.
- Loosen bolt on top of fuel filter can to enable fuel to push air up and out.
- Once all air is pushed out, tighten the bolt back up.
- Bleed air from high-pressure fuel pump by cranking engine without starting to build pressure and use wrench on injector nut to turn and allow air to hiss out and close. This should be performed on all injectors.
Diesel fuel injection maintenance tips
Diesel fuel injection systems should be cleaned and maintained every 36 months or 45,000 miles, whichever comes first, or more frequently for heavy-duty machines (such as long-haul trucks). For information on the required time and frequency of maintenance for your machine, vehicle, or fleet, contact the manufacturer.
In addition to the tips listed above, a few basic guidelines for regular fuel injection system maintenance include:
- Follow safety procedures before work.
- Change oil at recommended intervals.
- Change fuel filters every 10,000 to 25,000 miles.
- Use a wet sponge or something similar to wipe down engine bay.
- Use an old toothbrush to clean the nooks and crannies of diesel fuel injector systems.
- Use specialty degreasers to safely dissolve any gunk on engine or system components (consult your owner’s manual before using any products).
There are various fuel injection cleaning chemicals on the market that are meant to be run through your system, but you should consult your engine's manufacturer before doing so.
Diesel-powered devices are costly and essential to a company's operations, so it's critical to have them serviced by a professional. Your best bet is to have it serviced on a regular basis by a reputable, skilled technician.
Diesel fuel quality
Finally, the diesel fuel you use in your equipment has a significant impact on its performance. High emissions, wear on fuel systems, and poor engine performance can all be caused by low-quality diesel fuel. High-quality diesel has a lower sulphur content and provides excellent lubricity. Consult your manufacturer to find out what type of diesel fuel is best for your machine.
Low viscosity oils are required by several new engine technology. These high-tech, low-viscosity lubricants improve fuel efficiency, particularly in newer automobiles. Phillips 66 and Exxon Mobile, for example, have recently added full-synthetic CK-4 and FA-4 oils to their product lines.
CK-4 is compatible with many older oil types and can be used in both newer and older engines. It outperforms CJ-4 in terms of wear and oxidation prevention, is rated for highway and off-road use, and comes in SAE 15W-40, 10W-40, and 10W-30 viscosity grades. Even lower viscosity grades are being made available.
FA-4 is designed to withstand greater temperatures and oil pressures in engines manufactured after 2016. Because of the decreased HTHS viscosity, it is not backwards compatible, although it must pass the same testing as CK-4 fluids.
