Hi dave i have a 1993 jeep cheroke, i went to start it and it would only run 3 sec. replaced the fuel filter and then it would rev up to 1500 and slowley come back down, then choke itself out. now it
Hi dave i have a 1993 jeep cheroke, i went to start it and it would only run 3 sec. replaced the fuel filter and then it would rev up to 1500 and slowley come back down, then choke itself out. now it only runs 10 sec, i have replaced the fuelpump and regulator, i noteced when it is running i can not hear the fuel pump. and the fuel pressure is never above 7 psi with the return line closed. any ideas? Ben
Fuel pressure is 31 to 35 for a 4.0 engine, so 7 is too low.
I know but I can't get it over that with it running. It's almost like the fuel pump shuts off while it's running, and right before it dies it turns on and then shuts off.
Find your fuel pump relay and jumper the power feed directly to the fuel pump power wire, this should make your fuel pump run continuously, now test your pressure, it should be at specs, try to start the engine, if it starts and runs then you need to track down the problem with the pump circuit, if you have a low oil pressure fuel cut off then that is where to start as it could be open or you have an oil pressure problem.
I have tried jumping it and it works but if you start it leaving it jumped does nothing, and for the oil pressure it has a single wire sensor, so it would not be switched, unless their is another one I do not know about.
If you jump the fuel pump relay and the pump still won't make pressure then the pump is either bad or the wrong one.
I have found the problem! It was a ceramic resister that controls the fuel pump after start up it lowers the voltage to the pump so the pump lasts longer and it is not in any repair manuals, took 3 hrs of looking at online diagrams.
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