suspected intermittent fuel pressure drop

[AZ Moose]

2005 Expy ELT 5.4l been battling this for a year now, many new parts, problem persists. Engine cranks fine but it acts like it is fuel starved. Doesn't happen every time, 1/2 to 2/3 of the time. When it fails to start I turn the key off, then to run (just short of crank) wait 5 - 10 seconds, crank again. This usually starts the engine in 1 to 5 attempts. Parts replaced: Fuel pump entire, fuel pressure regulator on fuel rail, fuel modulator? electrical on top of frame rail, 3 fuel injectors. Symptom persists after installing new parts. No evidence of a leak. Chevron gas, fuel injector cleaners, symptom more pronounced in cold weather. about to trade this truck although I like it. No details on pressure readings, no codes in computer, no vacuum leaks.

 

[rice_classic]

I would get it hooked up to a proper diagnosis machine, not just a "code reader" since you're not seeing any CEL anyway. Usually a proper diagnosis can find things like intermittent computer failure, maf sensor failure, intermittent spark failure etc.

 

[stamp11127]

Nice to have all those new parts. Monitor the fuel pressure to see if is fuel related.

 

[Lostneye]

I agree to try and get it hooked up to a monitor to try and better diagnose.

But I will suggest also looking at the fuel pump driver on the driver side frame rail. From the factory they sit flush against the rail and the dissimilar metals tend to corrode faster than they should. The new ones have spacers to prevent this. Still look to diagnose before adding more parts.

 

[05expedeb]

I agree to try and get it hooked up to a monitor to try and better diagnose.

But I will suggest also looking at the fuel pump driver on the driver side frame rail. From the factory they sit flush against the rail and the dissimilar metals tend to corrode faster than they should. The new ones have spacers to prevent this. Still look to diagnose before adding more parts.

Good advice but if you read the original post you would see he has replaced the FPDM expect he called it a modulator. Also the FPDM is more prone to corrode in states that use salt on the roads not in AZ Although anything is possible

 

[AZ Moose]

Thanks for the ideas

Correct is was the FPDM that was corroded and replaced but the problem persists. Can anyone recommend a fuel pressure gauge? And where does it connect to the vehicle? I realized today that I never replaced the gas cap. If it is venting incorrectly could that cause this problem? Stamp11127 I have no reason to believe that it is electrical. Unless the computer is doing one really odd thing, but I will have the dealer run a diagnostic soon.
Thanks guys!

 

[05expedeb]

In reading abouts the parts you replaced I didn't see FUEL FILTER hopefully you replaced it but if not maybe you should. Since you replaced the FPDM I would recheck the connector to make sure all contact areas are clean and making good contact

 

[2005exp]

Can anyone recommend a fuel pressure gauge? And where does it connect to the vehicle?

https://www.youtube.com/watch?v=AeVTZz0od7Y

https://www.youtube.com/watch?v=SUxagOAVS5M

 

[AZ Moose]

Thanks for the video reference, that helps. The fuel filter was replaced a year ago. I picked up a new one tonight as well as a new fuel cap. I will update this weekend. Thanks all!

 

[mystik]

If this is happening intermittently, then you turn off the key, wait a few minutes, then the truck starts. It sounds to me like the security system might have an issue. When you turn the key off, it seems like your resetting the PATS system. I would look into either the key chip or the PATS system its self. Just my opinion