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Fix my junk

I

InlandZJ

NAXJA Forum User
Location
Riverside
Any moble technicians hasta dam thing wont stay running. I think its fuel related again. Cranking and she wants to kick on but nothin.
Almost home tonight and gased it out of a turn and she shut down. Whats the Fuel pump life expectancy ?
 
Get a fuel pressure test kit at Harbor freight. Hook it up to the little schrader valve on the fuel rail and see what ya got. (I'm having a brain fart and can't remember what normal rail pressure is though)

When you first turn the key to "on" position you should hear the fuel pump pressurize the system. Is that happening? When was the last time the fuel filter was changed?
 
Pressure at the rail should be about 50-60 psi I believe. I had a problem with my pump low on power barley idled. Checked and found I only had 25 psi at the rail. Of course mine is an Xj so I don't know if the pressures will be exactly the same. But fuel injection pressures should be basically about the same across the board, give or take a few psi.
 
jumpnjeep said:
Pressure at the rail should be about 50-60 psi I believe. I had a problem with my pump low on power barley idled. Checked and found I only had 25 psi at the rail. Of course mine is an Xj so I don't know if the pressures will be exactly the same. But fuel injection pressures should be basically about the same across the board, give or take a few psi.
Click to expand...

Sounds kinda like the same problem idling just barely at a stop light almost wants to die. I also have the 4.0 I6 might be the same motor
 
Yeah it pretty easy. Just be careful not to get fuel everywhere. Look for the schrader valve on the fuel rail. Looks like the tip of a valve stem on your tire. The tester will screw right onto that and have a helper turn the key on. Pressure guage should jump to about 41 psi. Have your helper start it and it should drop to 39 psi "running".
 
Last edited:
Sounds about right, starts at about 40psi when the key is turned on and jump to about 56ish running. But like I said they should all be roughly the same giver or take a few psi.
 
How would it jump 16psi when the engine is using fuel, vs the pump running with no fuel use?
My experience has been similar to CaliXJ - mid 40's key on, 39 running.
 
souske said:
How would it jump 16psi when the engine is using fuel, vs the pump running with no fuel use?
My experience has been similar to CaliXJ - mid 40's key on, 39 running.
Click to expand...

Because when the system first primes itself it only runs for 3seconds, doesn't always get to full pump pressure. Once started the pump runs continuously and you get full pressure, also if you watch the guage and give it a quick rev you should see a small spike in pressure from when the pressure regulator loses vaccum and closes down to block the return line.

But again I'm not trying to preach that every car is exactly the same, just similar. You can test 3 cars in row and get 3 different results but they will all run the same way.

I hope some of my descriptions are helpful and at least clear enough to understand! :D
 
Thanks fellas, went to work all day and then came home to find the distributor cap and rotor were burnt. I looked up my receipt and i changed them in october last year. Fuel pressure was good just checked by pressing the valve and sprayed a little trying not to go crazy and have it all over. Thank you guys for the trouble shooting suggestions i really appreciate it. Also i snuck up on my little oil leak that i couldnt pin point, it was commin out of the oil sensor just above the oil filter. Dripping from the tiny boot on the wire connection end.
 
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