Fuel pressure vs volume

[fletcherson]

Hey guys, I have worked on machines for near fifty years and am a fairly competent mechanic but some times get a humbling lesson. Case in point: my fuel injected ford truck was giving me issues. The first thing I checked was fuel pressure and regulator function... all good. I then systematically tested near every sensor on it, map, tps, cts, 02, etc and so on. I was ready to start throwing parts at it when I decided to start by replacing the fuel filter. Guess what, fuel pressure will fool you. My initial diagnosis was correct but having adequate pressure and regulator function fooled me. The fuel filter, which is the size of a oil filter, was very restricted and was causing the problem. Just a FYI, hopefully someone will benefit from my misery, embarrassment, and shame, lol...

 

[Spanky]

Hey, don't feel bad. You solved it BEFORE you started 'throwing parts at it.' Way to go!

 

[dwsatt21]

Did you check the pressure when it was idling or at wot? I’m guessing at wot, you’d would have seen a drop in pressure. Fuel filters have probably gotten the best of most of us. I know I’ve chased down some problems that ended up being just that.

 

[Indycars]

Every once in awhile we need a reminder!

 

[fletcherson]

Did you check the pressure when it was idling or at wot? I’m guessing at wot, you’d would have seen a drop in pressure. Fuel filters have probably gotten the best of most of us. I know I’ve chased down some problems that ended up being just that.

Yes, it was fine, for a short burst in the shop, it even increased when vacuum dropped as it should. I even removed the fuel cap to see if there was any variance. It fooled me. In retrospect, had I drove it with the pressure gauge on perhaps it would have showed up. I was ready to put a ignition module in it, lol... thinking it was a intermittent failure. Then again I don’t remember the last time I changed it so I probably deserved it!

 

[31 bucket]

I was just going to ask the same question. Mine is supercharged with dual carbs. My electric fuel pump is screaming. And my pressure is low. Sitting the pressure goes to zero as soon as I turn it off. Have no return line. Plus pull up to stop and pressure goes to zero. I have been scratching my head

 

[old round fart]

Sounds like hurt fuel pump or clogged filter or pickup problem.