Requesting help with challenging NO-START diagnosis.

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

yes im sure the Crankshaft sensor directly afftects power to coil and fuelpump

edit. just re-read you have a 2000. no coil as 99 and earlier. try a obdII code reader if you can

Thanks Ryan

Try this to see if it works. I had the same problem with my 97 and doing this little bit did the trick. It is worth trying even if it does not work for you.

http://www.ilovejeeps.com/forums/showthread.php?t=17188

Basicly, I cleaned the computer connections and it fired right up. No problems since.

Thanks Mikey,

I previously disconnected & reconnected them, but will try cleaning them as well.

Have you check the starter to make sure it is functioning properly and making contact with the flywheel. If it is a fuel issue, carb cleaner in the tb should make it start.
That only means it must be a spark issue. I would try CPS or coil.

Thanks Jess,

The starter is engaging, and turning the engine over as normal.

There seems to be an electrical issue up-stream of the fuel pump relay keeping it from tripping and powering the fuel pump. Fuel pump works fine if you jumper around the relay.

Starting fluid or fuel in the intake haven't allowed it to start. Jumpering the fuel pump and trying to start hasn't allowed it to start.

Thanks all for the replies.

my brothers 97 XJ had similar problems, pulled the CPS and the plastic was worn all the way through to metal. Not saying its your problem, but it's not a bad idea to replace it and keep the the old one as a spare. good luck

Thanks Ryan,

Local shops do not seem to have a crank pos. sensor in stock. I'll see if I can borrow a scanner somewhere, and locate a CPS.

Any time you pull any plug apart for any reason CLEAN IT. I have a box of good senor's that people have replace because of bad or dirty plugs.
As away clean inspect retest then replace if needed.