XJay_97
NAXJA Forum User
- Location
- Livermore, CA
2000 XJ, 4.0L 6cy, auto trans, approx 96k miles.
Drove home from work, "no-bus" dash issue has been intermittantly occuring over the last few months, ran/drove fine, parked in the driveway same as any other night. Next morning the truck turns over, but never starts. Seems to turn over faster than typical startup, as-if there were less resistance.
Talk to a knowledgable guy at work, he says he has seen similar problems with other vehicles, and it was always the fuel pump.
Purchased a fuel pump, dropped the tank, swapped it out, same problem. Frustrated, now I bridge/jump the fuel pump pins in the power distribution module and the fuel pump runs fine. (Lesson: good diagnosis can save a lot of time & money swapping parts.)
Install a new fuel pump relay, and also swap & replace the ASD relay. No difference.
Drain the fuel manifold pressure through the shrader valve, pump still doesn't come on when key is on.
So the fuel pump relay is getting power, but does not pass it to the fuel pump. Without the jumper, the fuel pump does not run regardless the key position.
I leave the fuel pump jumper in, and try to start: no good.
I look into checking for a spark also. Since the 2000 has the coils on the plugs, I don't know a method to check for spark. I spray starting fluid into the intake while my wife tries to start it. No good. Cranks and never even tries to catch.
My Haynes manual provides a method to check the crank position sensor. I pull the connector, and check resistance between pins 2 & 3: no continuity, open. So the cps should be ok.
No check method for the cam position sensor.
Try starting the truck in neutral instead of park, no good. Cycle the shifter several times and try park & neutral again.
Just about ready to have a long discussion with my buddy Jose Cuervo...
I am reluctant to take it to the local dealership yet, haven't had good luck with their diagnosing ability.
- If the crank position sensor was bad, would it affect the fuel pump control circuit?
- If the cam position sensor was bad, would it affect the fuel pump control circuit?
- Any suggestions for other diagnosis to perform?
- Do these symptoms & tests lead conclusively to the ECM/PCM? Any tests to verify bad ECM? Is the ECM a purchase and install operation, or does it need to be programmed prior to install?
Thanks in advance
Drove home from work, "no-bus" dash issue has been intermittantly occuring over the last few months, ran/drove fine, parked in the driveway same as any other night. Next morning the truck turns over, but never starts. Seems to turn over faster than typical startup, as-if there were less resistance.
Talk to a knowledgable guy at work, he says he has seen similar problems with other vehicles, and it was always the fuel pump.
Purchased a fuel pump, dropped the tank, swapped it out, same problem. Frustrated, now I bridge/jump the fuel pump pins in the power distribution module and the fuel pump runs fine. (Lesson: good diagnosis can save a lot of time & money swapping parts.)
Install a new fuel pump relay, and also swap & replace the ASD relay. No difference.
Drain the fuel manifold pressure through the shrader valve, pump still doesn't come on when key is on.
So the fuel pump relay is getting power, but does not pass it to the fuel pump. Without the jumper, the fuel pump does not run regardless the key position.
I leave the fuel pump jumper in, and try to start: no good.
I look into checking for a spark also. Since the 2000 has the coils on the plugs, I don't know a method to check for spark. I spray starting fluid into the intake while my wife tries to start it. No good. Cranks and never even tries to catch.
My Haynes manual provides a method to check the crank position sensor. I pull the connector, and check resistance between pins 2 & 3: no continuity, open. So the cps should be ok.
No check method for the cam position sensor.
Try starting the truck in neutral instead of park, no good. Cycle the shifter several times and try park & neutral again.
Just about ready to have a long discussion with my buddy Jose Cuervo...
I am reluctant to take it to the local dealership yet, haven't had good luck with their diagnosing ability.
- If the crank position sensor was bad, would it affect the fuel pump control circuit?
- If the cam position sensor was bad, would it affect the fuel pump control circuit?
- Any suggestions for other diagnosis to perform?
- Do these symptoms & tests lead conclusively to the ECM/PCM? Any tests to verify bad ECM? Is the ECM a purchase and install operation, or does it need to be programmed prior to install?
Thanks in advance