Engine/Transmission (1998.5 - 2002) fuel psi 15 to 2 in 5 seconds of startup?

[nunya]

same reading on a mechanical liquid filled hooked up to hose, no guts in schraeder valve? I have checked all the electrics also and they both match, goes to the dealer on Mon. , guess it looks as if the lift pump blues have struck! Had been reading a low of 6 under load and 29lb. boost! 10 goin down the road. Thoughts????????

 

[FourBarR]

where are you taking the pressure at ?pre or post filter or at the vp44? if its pre filter could be plugged filter. probably lift pump . you could put a gauge in pre filter to check lift pump, assuming you are not now taking the pressure there. hope this helps.

 

[RabidRam]

where are you taking the pressure at ?pre or post filter or at the vp44? if its pre filter could be plugged filter. probably lift pump . you could put a gauge in pre filter to check lift pump, assuming you are not now taking the pressure there. hope this helps.

exactly what he said... best case scenario... blocked filter... otherwise, best guess is your lift pump is on the way out.



Dave

 

[Horsepuller]

I get 15 psi at idle, drops down to 10 under load, uphill. Lowest has been around 8. BTW, mine is located post filter at the check valve.

 

[jamnram]

Nunya,



I had the same problem (mine went to 0 after running for 5 secs), took it to the dealer, they said pump was fine and my gauge was bad. Bought a new lift pump, installed it and presure returned to normal.

 

[nunya]

thanks for all the help! The filter was the 1st thing I changed, only had 8,000mi. on it, made no difference. Hose is hooked to the VP schrader port so I outta see good psi I would think? Oh well, Monday at the dealer will tell, guess they do a flow test also?

 

[Sixpack]

same reading on a mechanical liquid filled hooked up to hose, no guts in schraeder valve? I have checked all the electrics also and they both match, goes to the dealer on Mon. , guess it looks as if the lift pump blues have struck! Had been reading a low of 6 under load and 29lb. boost! 10 goin down the road. Thoughts????????

I had the same problem with pressures. I took it in to the dealer and they replaced the lp no questions asked. Good luck!

 

[MRoberts]

I had the same thing happen to mine, one day after installing a FP gauge. The dealers will do a "flow" test first ( it will probably pass ), if it doesn't pass, then a pressure test. If it passes ( flow ), good luck on getting them to replace it under warranty! I had to go to two dealers to find one that would replace mine under warranty. The first dealer, who I have purchased two trucks from, would only do the flow test ( it passed ), wouldn't do a pressure test and wouldn't replace the pump. The second dealer replaced it on the spot, even though I had never set foot on their lot.

 

[nunya]

dealer did great

Lift pump installed no problem! Tech loved the setup for the fuel psi guage and it now reads 16 and 14 to 10, much better. Thanks for the replies. Don`t forget to bleed the lines to the guage on install. By the way the mileage is 36,650 so we will see how long this lives

 

[rweis]

My . 02



I think it is the flipping check valve opening and not seating corectly. I put a bypass regulator on my lp and set it to 12 psi. I measure pre and post ff. I get 12 or 12 or 12 or 12 or 12 or sometimes 10 pulling a 13k 5er.



I have not run extensive test though, only 42k so far on origional lp (on the frame by the tank)



Bob Weis

 

[Horsepuller]

When you say bleed the fuel line to the guage, do you mean to the sender? When I installed my FP gauge, I didn't bleed the line and this is probably why it took a couple good cranks to get the engine started. Also, after just completing a good pull (9k lbs trailer) going up 6% grades for several miles, the FP gauge wouldn't fall back to zero after engine shut off. It remains at 1lb pressure after the engine is off. Trapped air?

 

[rweis]

I have a guage post ff and just before the VP. When I replace the ff I crack the line to that sender (and put the sender over a bucket with a rag on top of it) and do the bump the lp thing.



The loose fitting just before the VP will dump fuel into the bucket bleeding all the air out of the fuel line to the VP (except in my case the last 3") and then the CTD starts right up, no continuous cranking.



It also assures the sender is not seeing air and therefore reads correctly. I retighten the line while the lp is doing its bump thing so I have positive pressure spraying fuel out at the loose fitting.



Works best if there are two people doing it, else you have to be QUICK to get from the bump to the fp fitting and tighten it to seal it.



Bob Weis

 

[Horsepuller]

Ahhh, that explains the problem I had. If I was to loosen a fitting closest to the VP, it would be at the schrader check valve where I have attached my 18" line that goes to the FP sender. So should I bleed it here at the check valve or at the sender?



One other question, is it a big deal if I don't have the sender mounted on the engine. I have mine mounted on the driver's side fender well.



Thanks

 

[nunya]

Hey, glad I started this! Hope it helps a few. I put a T at the sender and a hose with a radiator draincock on the end of it, put it in the bucket and bleed as much as neede and it`s a one man operation, the tech that changed the pump sure liked it! Good for FF changes too! Thanks for all the input

 

[rweis]

I loosen the fitting and retighten it under pressure because I do not want to add any possible points that air can get into the fuel system.



As far as to where to do it? As close to the VP as is practicle. Mine is about 6" before the VP and I probably do get some air in the line, but not much. You could do a ****** flow test as well if you ever wanted to do that.



Seldomly one best location for everybody



Bob Weis