Fuel Filter Warning Light

[jim x 3]

Truck is a 1988 F-350 dually NA in stock condition with 240,000 miles. Mechanical lift pump.


Symptoms: Filter Warning light illuminates upon heavy acceleration. Engine stumbles and truck barely accelerates. Problem gets progressively worse until filter light comes on any time above 1000 RPM. Engine stumbles badly and dies. Truck starts and idles normally.

Action: Although fuel filter was replaced 5000 miles ago, it was again replaced.

Result: Old filter looked extremely clean. Symptoms persist with new filter.

Action: Fuel pressure tested during cranking at test port on fuel filter assembly.

Result: 2 PSIG.

Action: Fuel lift pump replaced with a new mechanical lift pump.

Result: Symptoms persist.

Action: Rubber fuel line removed from lift pump input and 60PSI air used to back purge fuel lines from lift pump location thru FSV to tank. Some initial resistance to air flow following by vigorous bubbling in front tank. When air was removed, fuel flowed quickly from open rubber fuel line (where there had only been a trickle previously)

Result: Truck runs at all speeds with power and no stumbling.


Since my tank goes "empty" at 1/4 level, I guess its time to fix that problem and simultaneously clean the crud out of the front tank.


Regards,

 

[icanfixall]

It sounds like something got sucked up in the fuel lines and is trapped in the switching valve now. Crud in the front tank sounds really bad. Thats an easy tank to pull the sending unit from and dropping it is just as easy too. Just be careful of the fuel in the tank. It will make balancing the tank impossible when you drop it.