Topic: Jeep "Hickups"

[sharpxmen]

Ok, picked up a fuel pressure test kit from Harbor Freight last night and I will give her a test today. What is still baffling me is that that damn thing stalls out at the same spot every day. It runs just fine until I get to that sharp turn. Backfires every time and looks like I cant drive a stick. Annoying, very annoying. But still, why would this happen only after being driven for about 20 minutes?

maybe some paranormal activity - did you try another route?

[Steve-0]

Ok, I really have no idea what I'm supposed to do with this pressure tester. I mean, I know how to hook it up, but what do I do with the readings? I turn the key and it goes to 30psi, then slowly drops and stays steady at 7psi, but that's probably because the damn thing is leaking gas a little bit. Can I use plumbers tape on this or will the gas just eat it up? Also, took another route today and its not the route thats the cause (obviously), its the drive time. So after it gets warmed up (15 min of driving) it starts stalling and bucking, RPM drops frantically and the more I drive the worse it gets. I can power through most of the stalling but at a light throttle pressure it really goes nuts. Wasn't sure if I was even going to make it to work this morning. Doesnt do it at idle, but at all other RPM ranges, it is nasty. Let her cool down and shes good to go again. I know that a faulty pump can show up sometimes after it warms up, so thats a clue i guess. But I think I need some help on the gauge tester and another hand to maybe pinch the fuel line to test the pump. The pressure is at 35ish, then drops as it leaks. Then while running its about 37ish and if I rev it up a bit it goes to about 45ish then drops back to 37ish. When it gets warm, what am I going to be looking for?

[sharpxmen]

Ok, I really have no idea what I'm supposed to do with this pressure tester. I mean, I know how to hook it up, but what do I do with the readings? I turn the key and it goes to 30psi, then slowly drops and stays steady at 7psi, but thats probably because the damn thing is leaking gas a little bit. Can I use plumbers tape on this or will the gas just eat it up? Also, took another route today and its not the route thats the cause (obviously), its the drive time. So after it gets warmed up (15 min of driving) it starts stalling and bucking, RPM drops frantically and the more I drive the worse it gets. I can power through most of the stalling but at a light throttle pressure it really goes nuts. Wasnt sure if I was even going to make it to work this morning. Doesnt do it at idle, but at all other RPM ranges, it is nasty. Let her cool down and shes good to go again. I know that a faulty pump can show up sometimes after it warms up, so thats a clue i guess. But I think I need some help on the guage tester and another hand to maybe pinch the fuel line to test the pump. I think I also need to tell you what the pressure is when running. But I also think I need to get 2 readings right? One at cold and one at hot (stalling temp).

the fact that it drops quickly to 7 psi could mean the FPR is faulty, the check valve in the pump leaks or that one of your injectors leaks badly (or at least 1 to be more specific). When you start the engine you should have 31 psi at idle and if you remove the vac line on the back of the FPR should jump to 39psi - that's the readings you should have both hot and cold and while driving (at wot you should always have 39psi, decelerating or in engine braking you will have less than 31 since your vacuum would be more than at idle). best if you can monitor the pressure while you drive it but if it has the problem while stopped and you are revving the engine you should still see if the pressure is an issue - best to have the vac port removed and plugged (on the line side) with a little screw or bolt or something like that so you're not thrown off by the vacuum - in that case it should always show 39 psi regardless of the throttle position or rpm.

hope this helps.

PS: you say it's leaking, the schraeder valve is -4 AN fitting so unlike with the NPT fittings you cannot use teflon tape to seal it, just look inside the fitting that's on your gauge hose and see if it has an o-ring there, if it doesn't just tighten it hard and it should not leak, if it has an o-ring or some sort of rubber gasket inside (unlikely but you never know) then by hand should be fine

[Steve-0]

Sorry, need to clarify: The cheap ass gauge from Harbor Freight leaks, so the pressure dropped to 7 or so with the key on. While running it still leaks but is at the correct pressure. Just need to take the stupid thing back and make my own, with a hose long enough to take in the cab with me to see whats going on at the time of stall. Thanks for the info. I will try again later.

[sharpxmen]

you can use teflon tape at the gauge end of the hose

if you want to make your own use steel braided hose that is fuel resistant with pre-crimped -4AN female ends and a female 1/8 or 1/4 NPT (depending on your gauge) to -4 AN male adapter. Use teflon tape on the NPT threads, the -4 AN threads will seal themselves

[Steve-0]

Fuel filter.... 

[sharpxmen]

Fuel filter.... 

now i don't feel that bad for sounding like a broken record

[Steve-0]

  Thanks sharpx, you da man.

[sharpxmen]

Thanks sharpx, you da man.

no prob, glad you finally resolved the issue