SmichaelR22

HISTORY:

said truck is a 2001 6 speed SRW / 19.5"s 4x4 basically stock with juice / attitude added on with about 179K on the clock Truck is mostly used to tow a 12k enclosed goosneck through the mountains so i work it pretty hard but keep a sane eye on fuel pressure and egts while doing it on level 2 tow mode. holds 72 with the cruse pretty good at 10-11mpg the way i tow. I dont beat it or race it and its ususally on 1 while empty, 2 towing, and occasionally 3 for driving around city puffing a little smoke at hondas occasionally. truck has good power and no DTC's present in a long while.

PROBLEM:

last couple weeks upon startup (no starting issues) at idle my fuel pressure will be very eradic like 28 psi then 4 then 20 then 2, and after a couple blips of the throttle or a couple gear shifts pulling out of my driveway, it would be fine at 12-16psi for even a 6 hour towing trip. a restart in the same day would have no issue. only after it sat for 1-2 days would the flaky fuel pressure return for a few minutes, then be fine again. also, when i would "bump" the starter the lift would show about 26psi without the engine running.

MY ATTEMPT AT FIX:

i thought it might be the over flow valve sticking shut (high pressure) and then sticking open (low pressure) so i changed that with a dealer part (56$ with seals). thought was when i bump the starter i shouldnt ever see more than the over flow pressure setting. I let the truck sit for 2 days, and "bumped" the starter twice. both times showing steady 22psi. I then changed out the overflow valve, and upon "bump" of the starter i saw 14psi! both times! thought i was golden and set out for the 500mile weekend towing trip! was fine 250miles there! great! camped and fourwheeled for 2 days, and started it up sunday to head home. upon startup it was good stable pressure, no issues as normal. but then half way home it started to get flakey up and down and up and down again. seemed to get worse to the point i slowed down and took off the cruse to petal home. seemed like it did this for about 20 miles or so, then all of the sudden it was fine again.


CURRENT STATUS:

Yesterday morning to my short work drive it said 30 psi! a couple times up and down. now i am worried i read about blown diaphrams from too much lift pressure.... This morning and all last night i did some running around and no issues at all.

not sure where to go. i can get an OEM lift pump warrantied out for free, or should i be looking at a different problem / solution. if the LP was bad why would it have blips of high pressure? air leak? fuel filtration problem? VP44 problem?



yes i am aware of aftermarket lift pump solutions, that is not my question of which is best.


thanks in advance.
Mike

BarryG

Mike
I have had the same issue for several years and am baffled. My gauge may read 25psi then 2 psi in wild swings other times it will be rock steady at 15psi. May sit steady at 2psi for a while. There seems to be no rhyme or reason as to when full tank, 1/2 tank, empty tank, hot or cold, loaded, unloaded, stomping on it , cruising it is truely random. I have pulled my tank to check for problems within. I did change out the basket inside as the screen in the bottom of it had a tear in it thinking that maybe the flap of screen was getting sucked up causing a restriction. I replaced the supply line from the tank to pump, pump to filter and from filter to vp. I have thoroughly checked the filter canister and can find nothing wrong with it. I plumbed in a temp gauge to verify my "real gauge" and left it there for months. It mirrored my real gauge. I have had this problem with multiple pumps. I had a RASP mechanical pump for quite a long time and it did it with that. I put in a cam a couple years ago and at that time I put in a 12 valve mechanical pump since I now had a fuel pump lobe to drive it. It still does it. I even swapped out that pump with another one just to make sure it worked fine. I have swapped out the overflow valve or whatever it is called on the vp. I have tried leaving the fuel cap off to alleviate any vacumn created in the tank. I have taken my bypass valve out temporarily which I have set at 16psi and even though the 12 valve pump will peg my pressure gauge at 40psi without the bypass I have still had it happen. I have considerd the VP44 as the culprit(somehow freeflowing fuel through it to the rerturn) but cannot justify $1000 to find out. The truck runs fine even great when it shows little to no pressure towing in the mountains when it acts up. I have gotten to the point that I dont worry about it too much as I have rationalized that whatever is causing the pressure flucuations must not be affecting the volume or I would notice fuel starvation symptoms at times and I never have noticed that.
So while I dont have an answer to your problem I do feel your pain and if you figure it outplease post up as I would love to get it fixed if for nothing else peace of mind..

SmichaelR22

its really odd, i was ok with "it will be fine" when it did it upon startup pulling out of the driveway, but when it randomly does it while crusing and towing 400 miles from home, i get a little worried now.

Funny you mention the fuel cap. ever since i have owned the truck, when i tow and suck a full tank down in 5 hours non stop, the cap always has a whoosh of vacuum in the tank when opened. over normal use with a tank lasting 1-2 weeks i dont have that issue. maybe ill investigate a new fuel cap, or like you said try leaving it loose.

someone also suggested a secondary fuel gauge to confirm the readings. i have a dummy light that goes off at 2psi i think i just have to hook up the wire the dealer ripped out while they took 4 weeks do find a bad 1400$ ecm last year. bah!

BarryG

If you are creating vacumn in the tank could be the rollover valve is going south on you/clogged. It is on top of the tank and is also the tank vent. If using a tank of fuel over several days it probably has plenty of time to slowly release the vacumn.

Ed ke6bnl

if it is and electric pressure gauge maybe the sending unit is going south. Depending on where you mount them the IP pulses can destroy the the sender. I have mine near the front of the rear tire after the airdog pump.

SmichaelR22

it is a juice system i mounted the sensor where the instructions said to with the different banjo bolt thing on the supply line to the IP i think.

Have been driving it to work this week with no issues, but not towing. it should sit for a day or so this weekend to see if the problem repeats again.