Engine/Transmission (1998.5 - 2002) one more pressure q..

[CEpp]

its been going on for about 2 months now, the longer the truck idles still or in traffic and the warmer it gets my fuel pressure starts climbing. ive seen it as high as amost 20 psi! with a factory style l/p, l/p has been replaced and prob still there, could it be the guage or maybe the isolator, or maybe the pressure relief valve? then it reads 20 i shut the truck off and refire it and the pressure is back down to 12 psi. has anyone had this prob? when it is reading 15 or more i can still drag it down a few at wot, just as if it was sitting on 12. please help...

 

[SpicyJam]

I am in the same boat. Mine fuel pressure gauge from Dakota Digital is reading 23psi at idle 70mph 21 and WOT 12psi.



I have the banjo bolts from Geno's and the tapped one is in the injector pump. The truck just had its' lift pump replaced and before that pressure was 17psi before the pump went went bad.



A little help for possible answers for the both of us would be great. Not that I am nervous about anything just would like to know why the dramatic change.

 

[CEpp]

i drove the truck last night on my way home from work and it started to climb, it stopped at about 20psi then when i got on the freeway it slowly fell to about 13, slow=about 10-15 mi. it hasnt pushed over 20 psi yet... and light a fellow tdr member could produce would help, guage or bleed off valve on vp44? as much as i would like to believe that a stock l/p could produce 20 psi at idle after approx 1 hr of running at slow speeds, i know its not possible and want to correct. .

 

[nieters]

mine starts out at 20 . i have a pusher pump installed.

when it warms up, i gain 1+ on the gauge.

there has to be a simple chemistry/physics answer.

 

[SpicyJam]

I am not worried about mine at all. When I turn the key the gauge hits 26psi at start up. Then sits at 23 at idle. 20-21 at freeway speeds. I am able to pull it down to 12psi at WOT. So as I wouldn't worry about yours either, and yes mine is a stock L/P.

 

[CEpp]

well it doesnt start out at 20 it starts out at 10, then builds to 20 in about 30 min of intown driving then if i jump on the freeway it falls to about 12 after about 20 min. ?

 

[Ron Bissett]

Sounds like air in system , do check gauge with other gauge that is known to be good . Ron Bissett in Metro Louisville Ky

 

[CEpp]

no air in system, sounds like pressure is building and falling but not bleeding while its running or its a junk guage or isolator ? it doesnt jump around like i think u think, super slow climb and fall. ive had air and it jumps all over the place. .

 

[dieselsam59]

Is your gauge pre or post filter? If it is before the filter you could be building pressure against a clogged filter. When you turn the truck off the dirt or debris settles away from the filter. Then gets sucked back in

 

[CEpp]

after filter, but i just replaced the filter wk ago when i changed the lift pump and this prob was there before i changed the l/p and the filter. fleetguard filter as well

 

[dieselsam59]

i was looking in the shop manual, there is a overflow valve on the side of the injection pump which should bypass fuel back to tank if over 14-16psi

 

[Ron Bissett]

Is your gauge a all electric or is it a Machanical with a isolator ? if its machanical with a isolator could be bad diafram . If all electric from the sender, is sender off the motor? do you have the sender grouneded with a ground wire from case to a good ground? Did you check with other,"known" to be good gauge? Hope you find solution to problem. Ron Bissett in Metro Louisville KY

 

[Shelby Griggs]

I sometimes see 20 PSI on my S. P. A. digital, and I think I have seen the peak recorded at 30 PSI +. Real high and or low pressures that seem to correct themselves are I believe early signs of a weak LP. Why it goes way high I don't know, but I know last week mine did both the way high and way low like in a suction situation. During the real low extremes I know the LP wasn't running, because I shut the truck off and then bumped the starter, there was no LP running! It seems to be OK now, but I will drive with an eye on the LP. Number 4 seems imminent!



SHG

 

[John - K5AWO]

High Pressures:



Any possiblity that the high pressures after being on the road a bit are being caused from the fuel/air mixture in the tank rising with temperature?



Test for this by removing the tank cap and seeing if it has any effect on your fuel pressure.



If the fuel pressure drops to normal, I would suggest the tank's vent is plugged.