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Low fuel pressure may have easy fix

Question: I have a 2005 Ford F-150 with a 5.4-liter V-8 engine with slightly more than 97,000 miles. Recently, the truck has experienced intermittent losses of power. The check engine light hasn’t come on, but a gauge did indicate low fuel pressure.

I installed a new battery and two fuel filters (the first one was dirty). Also, two tanks of gas with fuel injector cleaner have been run through the system. This has not solved the problem. Do you know of any Ford recalls that address this problem? I would appreciate any suggestions you have to correct the situation.

– M.C.

Answer: Several things could be causing your problem. Finding a solution will require testing and verifying fuel pressure.

Your pickup employs a no-return fuel system that is unlike the return-based system used on most vehicles prior to 2000.

The fuel pump on earlier vehicles sent more fuel to the engine than needed. The engine-mounted pressure regulator kept the correct amount and returned the rest to the tank. Emissions regulations prodded carmakers to move toward no-return systems, which reduce fuel tank vapors.

Instead of a mechanical fuel pressure regulator, Ford employs a fuel pressure sensor and a fuel pump driver module, the latter of which varies voltage to the fuel pump.

Typical causes for low fuel pressure include a dirty fuel filter, weak pump, incorrect tank venting, restricted fuel lines, a clogged pump inlet strainer and faulty electrical control. But first, let’s look at a common fault. It’s easy to do.

The fuel pump driver module on Ford trucks of this vintage is known for corrosion-caused failures. The part is attached to a steel cross-member under the truck bed, near the spare tire. The module’s alloy metal housing reacts with the steel mounting and can corrode badly enough to expose the electronic parts inside to the elements, causing erratic operation or total failure. This is a much larger problem in areas employing road salt. I’d recommend dropping the spare tire and removing the module for inspection. If it lacks sealing integrity, replace it. The replacement part should come with rubber grommet standoffs and other upgrades to mitigate corrosion issues. I am unaware of Ford issuing a service bulletin or recall for this problem.

If your symptom continues, I’d recommend using a scan tool to check fuel pressure during low- and high-load operating conditions. A large difference points to a weak pump or restriction. Also, find out whether correct voltage is being delivered to the pump under all conditions. A faulty pressure sensor could be causing the system to operate incorrectly. It’s odd the fault isn’t severe or long-lasting enough to be recognized by the diagnostic system and trigger a check engine light. The dirty filter is telling us to get into the tank for a visual inspection of contaminants and possible pickup strainer clogging.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at [email protected]; he cannot make personal replies.


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