Topic: Fuel pressure

[jfrabat]

Quick  question: if I  prime thefuel pump  on my Jeep, but don't start the Jeep, the  pressure drops rather fast  (about 1 PSI per second more or less).  I am  thinking my fuel pressure regulator is not upto par, and that's OK (it's getting replaced by one of Sharpxmen's ones).  The  questionis, is there  anythinng else Ishould be looking at?

Also, when I dropped the tank today, I noticed a very small crack on the neck of  thefiller tube of the tank.  The tank still holds pressure, though.   Is this reason enough to go out and look for a new tank?   I also need a new gas skid, by the way.  Any suggestions?

[sharpxmen]

Quick  question: if I  prime thefuel pump  on my Jeep, but don't start the Jeep, the  pressure drops rather fast  (about 1 PSI per second more or less).  I am  thinking my fuel pressure regulator is not upto par, and that's OK (it's getting replaced by one of Sharpxmen's ones).  The  questionis, is there  anythinng else Ishould be looking at?

Also, when I dropped the tank today, I noticed a very small crack on the neck of  thefiller tube of the tank.  The tank still holds pressure, though.   Is this reason enough to go out and look for a new tank?   I also need a new gas skid, by the way.  Any suggestions?

it's either the FPR or the check valve in the pump. if it's all sound should hold pressure overnight or at least not bleed out completely (there should still be pressure the next day, but at a minimum if it holds some pressure for at least couple of hours should be fine)

[jfrabat]

Then I guess we'll  find out which   one it is when  I change the   FPR for one of yours...  I guess this  could  well   be the  reason  why the Jeep sometimes idles  too high (the computer "learns" the weak pressure and adjustsit accordingly)

[TrailsLessTaken]

OK the matco man just got me my fuel pressure gauge today.  I wanted to check and  see how my system looked before i got one of sharpxmen's to put in there.  When I turned the key on I can hear the pump kick on and I see the needle move but then it immediatly drops back to 0.  Then when I started the jeep it jumped up and held right about 30-31 with the vacum hose hooked up and then when i unhooked it, it would jump to 39 and then it would drop back to 31 as soon as i hooked the line back up.  when i shut the jeep off though it doesnt hold pressure, it drops right back to zero again.  So would this mean that the  FPR is working and the check valve is bad?

[sharpxmen]

OK the matco man just got me my fuel pressure gauge today.  I wanted to check and  see how my system looked before i got one of sharpxmen's to put in there.  When I turned the key on I can hear the pump kick on and I see the needle move but then it immediatly drops back to 0.  Then when I started the jeep it jumped up and held right about 30-31 with the vacum hose hooked up and then when i unhooked it, it would jump to 39 and then it would drop back to 31 as soon as i hooked the line back up.  when i shut the jeep off though it doesnt hold pressure, it drops right back to zero again.  So would this mean that the  FPR is working and the check valve is bad?

could be the FPR, the check valve or the internal o-ring. The more long shot would be a leak along the lines (but you would smell it) or maybe in the tank at the output of the fuel pump. Your pressures are exactly what they should be so the FPR holds pressure correctly but it could be that the seat is slightly leaking - it's not that big of a deal though just that you need to put the key on and wait for the pump to make a bit of pressure before cranking it

[TrailsLessTaken]

It runs fine once it's started, im just trying to go through and make a list of everything that needs attention since i have negelcted it the last few years

[TrailsLessTaken]

Will it not holding pressure when its off or after the pump tries to prime give me any problems down the road or is this something that I shouldnt really worry about for the moment?

[sharpxmen]

Will it not holding pressure when its off or after the pump tries to prime give me any problems down the road or is this something that I shouldnt really worry about for the moment?

if it's the check valve you'll be fine once you have it running. Internal o-ring on the FPR might give you problems at wot when there's flow leaking around it (so there wouldn't be enough flow to sustain the pressure), same for the valve seat but that is unlikely to leak that much to give you as much trouble. If it's a leak at the pump or the lines that can be more of an issue in time if it gets worse (same as with the o-ring). I'd say change the o-ring(s) first and see how it goes, takes 5 minutes and an 8mm wrench.

[TrailsLessTaken]

I will give that a shot tomorrow and see what i come up with

[TrailsLessTaken]

OK I pulled the FPR out and found the smaller gasket was ripped in two, and in my gasket kit the closet one I had was 5/16 ID and 7/16 OD and 1/16 thick.  Looking at the one that came out the ID and OD looked to be the same but I think it might have been 1/8 thick maybe.  I replaced it and primed the pump, and this time it held pressure.  When i started it up the needle on the gauge was bouncing, both with vacum and without but it was still near where it was supposed to be.  Could this be because of the gasket not being as thick?

[sharpxmen]

OK I pulled the FPR out and found the smaller gasket was ripped in two, and in my gasket kit the closet one I had was 5/16 ID and 7/16 OD and 1/16 thick.  Looking at the one that came out the ID and OD looked to be the same but I think it might have been 1/8 thick maybe.  I replaced it and primed the pump, and this time it held pressure.  When i started it up the needle on the gauge was bouncing, both with vacum and without but it was still near where it was supposed to be.  Could this be because of the gasket not being as thick?

it's probably the FPR being old and the membrane ready to go, seen that before, other FPRs are not doing it. But that being said it might be that the o-ring it get's pushed in and our and once the pressure drops would seal again so best to get the proper o-ring and try again (won't hurt, it is better to have the correct size anyway)

at least now you know what was causing the pressure bleed and that is not a leak or the pump

[TrailsLessTaken]

Well I dont think it should be bad I replaced the FPR in 2007, I wouldnt think it would go bad that quickly.

[sharpxmen]

Well I dont think it should be bad I replaced the FPR in 2007, I wouldnt think it would go bad that quickly.

then it's the o-ring

[neale_rs]

Responding to the skid plate question:

I bought an MTS gas tank (part number 0065) and it did NOT fit in a Kilby skid plate although the factory tank did fit.  So just a heads up on the MTS tank if you plan to install a heavy duty aftermarket gas tank skid plate.  They told me their tank will fit in the Warrior skid, so that may be the way to go if you don't need anything too heavy duty.