A diesel engine is only as healthy as the fuel reaching it.
Plugged filters, water in the fuel, air getting into the suction side, a weak lift pump, or a cracked fuel line can all cause the same symptoms: low power, surging, hard starting, stalling, or a fuel pressure fault. Left alone, some of those problems damage expensive high-pressure pumps and injectors.
Harbor trucks fuel at a lot of different places, and any tank of fuel can carry water or contamination. Trucks that sit part-loaded through damp coastal nights collect condensation in the tank, and a drayage truck that never fully empties its tanks gives that water somewhere to live. Fuel filters and water separators are the first line of defense, and they need attention on schedule — not just when the truck quits.
What our Fuel System Repair covers
- Primary and secondary fuel filter replacement
- Draining and servicing fuel/water separators
- Water-in-fuel sensor and warning diagnosis
- Priming the fuel system and bleeding air after filter changes or running dry
- Finding air leaks on the suction side — loose fittings, cracked lines, and bad O-rings
- Lift pump (transfer pump) testing and replacement
- Fuel line and hose repair and replacement
- Fuel tank crossover line and fitting leaks
- Fuel pressure sensor diagnosis
- Fuel heater and filter housing problems
- Checking fuel tank straps and brackets after a leak or impact
- Pulling a fuel sample when contamination is suspected
What can't be done on the roadside
- High-pressure fuel pump replacement on many engines, which can involve major disassembly and timing work
- Injector replacement on engines where the job means removing major components — some injector work is possible on site, but many jobs belong in a shop
- Fuel tank removal, cleaning, or replacement after heavy contamination
- Flushing a system contaminated with gasoline, DEF, or water all the way through the injectors
Put DEF in the fuel tank by mistake? Don’t start the engine — on many trucks, don’t even turn the key on, because that can run the fuel pump. DEF in the fuel system can cause very expensive damage. Call before you turn the key.
Fix it on site or tow it?
Filter changes, water separator service, priming, lift pumps, and most line and fitting leaks are standard mobile repairs. If the symptoms point to a fuel filter or air in the lines, fixing it on site usually has the truck running the same visit.
A tow may be the better call when contamination has already reached the high-pressure side, when a high-pressure pump or injectors have failed, or when a major fuel leak makes the truck unsafe to work on where it sits. Diesel leaking onto a hot exhaust is a fire hazard — shut the engine down and move away from the truck.
What to tell dispatch when you call
The more dispatch knows up front, the better the odds the mechanic shows up with the right parts and tools on the first trip.
- Symptoms: low power, stalling, surging, hard start, or no start
- Any fuel smell or visible leak, and where it seems to be coming from
- Fault codes or a water-in-fuel light
- When the fuel filters were last changed and where you last fueled
- Whether the truck ran out of fuel or had a filter changed recently
Truck makes & engines we work on
- Freightliner
- Peterbilt
- Kenworth
- Volvo
- Mack
- International
- Western Star
Class 6 through Class 8 trucks, including engines from Cummins, Detroit Diesel, PACCAR, Volvo, Mack, Navistar, and Caterpillar.
Fuel System Repair around the harbor & the South Bay
We handle fuel system problems in yards, at docks, and on the shoulder. Low-power and stalling complaints often show up under sustained load — pulling a loaded box up the Vincent Thomas grade, or merging onto the 710 from Ocean Boulevard — when a partly plugged filter can’t keep up with what the engine demands.
Freeways
Service areas
Fuel System Repair FAQ
What are the signs of a clogged diesel fuel filter?
Loss of power under load, surging, hard starting, and low fuel pressure codes. A filter can flow enough at idle but starve the engine when it’s working hard.
How often should diesel fuel filters be changed?
Follow the engine manufacturer’s interval for your truck and duty cycle. Trucks that fuel at many different stations or see water-in-fuel warnings may need more frequent changes.
Why does my truck die right after a fuel filter change?
Air in the system. After a filter change the fuel system has to be primed correctly; skipping that step, or a poorly seated filter, lets air in.
I put DEF in my fuel tank. What should I do?
Don’t start the engine, and on many trucks don’t turn the key on either. Call for help right away — the tank and fuel system may need to be drained and flushed before the truck is started.
Can water in diesel fuel damage my engine?
Yes. Water causes poor combustion and corrosion and can damage high-pressure pumps and injectors. Drain the water separator when the warning comes on and have the source checked.
Do you replace injectors?
It depends on the engine and access. Describe the symptoms and engine model when you call, and dispatch can tell you whether it’s an on-site job or a shop job.