Engine/Transmission (1998.5 - 2002) lift pump pegging the pressure gauge

[azpete]

Used to run 14 at idle and 12 1/2 cruising. Now after the motor has warmed up any peddle pressure will peg the gauge or it runs at max now matter what the RPM, even full throttle. Hooked up my mechanical gauge and sure enough 19lbs. at idle. Will drop to 15 reving the motor to 2600. Any cause for concern or do I have a really good pump all of a sudden?



Couldn't take it for a test drive with the mechanical gauge because it would not seal right, deisel all over that side of the motor. Do you guys clean it off with something or is it alright to just leave it alone?



Pete

 

[DavidC]

Pete,

The only that comes to mind at the moment is high voltage to the pump actually making it run faster. If this is case damage could occur to alot more than the pump. I would at least check with a DMM.



Dave

 

[Fishin Guide]

Used to run 14 at idle and 12 1/2 cruising. Now after the motor has warmed up any peddle pressure will peg the gauge or it runs at max now matter what the RPM, even full throttle. Hooked up my mechanical gauge and sure enough 19lbs. at idle. Will drop to 15 reving the motor to 2600. Any cause for concern or do I have a really good pump all of a sudden?



Couldn't take it for a test drive with the mechanical gauge because it would not seal right, deisel all over that side of the motor. Do you guys clean it off with something or is it alright to just leave it alone?



Pete

Sounds like the overflow is not opening all the way.



I don't know if it'll hurt the electric motor or not if the voltage is not right, but it probably would not be a good thing.



I use a little foamy engine brite on the block when it's cool. works liek a charm. If you have really heavy fuel depositis, use some mineral spirits and rub in real good. Then rinse with water. I follow that up with the foamy brite and it's always clean.



Dave

 

[DavidC]

Now there's a thought on the overflow valve, could also be a problem with the return line or maybe the vent on the tank (pressurizing tank). You could try leaving the fuel cap off and see what happens.



Dave

 

[Steve St.Laurent]

There's an internal bypass in the lift pumps that regulates the pressure the pump puts out. Sounds to me like your valve is sticking. The overflow valve is in the VP44 - I doubt that's what's causing it. I personally wouldn't worry about 19 psi (I run 20) but you might want to keep an eye on it and make sure it doesn't go really high. This is one of the failure modes of these lift pumps (bypass valve sticking causing high fuel pressure).

 

[azpete]

Thanks for the ideas. Will try them out today. I have my spare ready to put on if need be. It's time for either the Vucan relocate or the Rasp and be done with it, will decide which way to go this weekend. Right now the little lady says she wants the bedroom painted and NOW.

 

[tgee]

What's the highest pressure you saw? Do you have the 15 or 30 PSI gauge? Usually high pressure is caused by a restriction in the return line, or a defective overflow valve. Sometimes high pressure means less flow, which is not good.

 

[azpete]

I have the 15lbs gauge. Just looked in the Geno's catalog and $222 for the 30lbs!! Replaced the original LP 2 years ago with almost the same problem. Only difference was idle pressure went down to 12 and any throttle would increase fuel pressure. New pump and problem solved. Just replaced the VP44 about 3 weeks ago and with my Alzheimers I just can't remember if the problem started just before or after the replacement. Will replace the LP next weekend and see what happens.



If it's the VP can the overflow valve be replaced without pulling the VP?

 

[Fishin Guide]

I have the 15lbs gauge. Just looked in the Geno's catalog and $222 for the 30lbs!! Replaced the original LP 2 years ago with almost the same problem. Only difference was idle pressure went down to 12 and any throttle would increase fuel pressure. New pump and problem solved. Just replaced the VP44 about 3 weeks ago and with my Alzheimers I just can't remember if the problem started just before or after the replacement. Will replace the LP next weekend and see what happens.



If it's the VP can the overflow valve be replaced without pulling the VP?

Yes. It can be pulled in about 5 minutes without removing a thing!



Dave

 

[azpete]

Thanks Fishin Guide. Nice to know that I won't have to pull the VP again if thats the problem. Still haven't decided on the relocate or Rasp. Pressures have been ok last couple of days.

 

[EGaskamp]

Is the overflow valve underneath the banjo bolt just to the left of the VP inlet? Thanks



Eric

 

[Fishin Guide]

Is the overflow valve underneath the banjo bolt just to the left of the VP inlet? Thanks



Eric

It's just left of the inlet. That banjo on there is your return line.



Dave

 

[MPlunkett]

Pete,



Unrelated to this thread, but my problem was a TC, not the ECM or VP... bite the bullett and ordered a DTT today... ... . Know any good transmission shops?... ... .

Thanks for your earlier help. .

 

[azpete]

OOOUCH! Sorry to hear that. Haven't been to a transmission shop around here for years and years. Maybe if you posted a new thread some of the local guys might know of someone. If you don't mind driving 1 1/2 hours call Fred Swanson and see what he would charge you. I remember spending alot of road testing time with him after mine was installed, holding the pressure gauge from under the truck through the passenger window to make sure the line pressures where just right at each shift and other adjustments. Then he proceeded to demonstrate the lockup of the TC by removing 5000 miles worth of rubber from my 4 back tires in a 20ft. stretch from a standing start. :-laf