Engine/Transmission (1998.5 - 2002) thought i had a handle on this....

[IStivison]

after searching the forum and talking to may people about fp, im getting people telling me under 10psi= bad news for lp(what i always thought), but after reading many threads, some are saying 5psi=. my guage is reading 5psi, my personal mechanic buddy is saying normal. guy @columbus diesel is saying low. i have the intank pump#@$%!. was ready to buy fass, but now unsure if lp is on its way out or not

 

[JFaughn]

Thats why the VP pump is so problematic , but you did not say under what conditions , WOT- wide open throttle 5-7 lbs , sounds right , higher 10-14 lbs at low RPMs .

 

[IStivison]

stays @5 psi, no fluctuation up to 40 mph. drove home after hooking fp guage up and parked it til i could figure it out.

 

[ThrottleJockey]

Pick one. Do you want to buy a FASS or an injection pump?



Ask any of these guys the fastest way to murder a VP.

 

[obert]

I have a stock LP relocated with 1/2" vulcan kit, wont go below 10psi WOT at top RPM.



Works for me, but I'm not asking for that much-- not much for feuling mods.



Question is: How long will it last??



5psi is a little low. Those guys down at CDS (assuming Col's OHIO, on integrity dr. ) wont steer you wrong, they do alot of high performancece stuff, too.

 

[rweis]

VP44 calibration is 13. 5 psi.



Bob Weis

 

[JohnHaney]

i have the mods in my signature, with the bd high volume relocation pump. at idle i see 15-16 psi and 13-14 psi at wot. i have been told that 5 psi is the absolute minimum at wot, should be around 13 psi at idle like bob posted. i would be concerned with the longevity of the lift pump with fp that low at idle. when you compare the cost of replacing the lift pump vs. the injection pump, it is worth while to be proactive.

 

[rweis]

Actually, as I understand it, during the calibration of the VP44 the fuel psi is held at 13. 5 psi regardless of the rpm. Which implies 13. 5 psi is optimum under all and any conditions.



However, I think +-3 psi is acceptable based on the maximum deflection of . 5mm of the diaphram between the low pressure side and the high pressure side. The diaphram also has seals that seal it and the two sides and +-3 psi I think is generally acceptable tolerance before the seals start to deform.



Bob Weis