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Start then dies

Posted: May 28th, 2023, 7:37 am
by MilehighGS
Hi all! Just installed my first 4.6 build and ready to fire it up. It's a 2000 xj and fires right up..........but then it dies.......I've replaced fuel pump, checked wiring........looked for the fuel pump ballast.........nothing. Hope anyone can help me.

Re: Start then dies

Posted: May 30th, 2023, 7:06 am
by TJBUD
Milehigh,
Not any takers on this thread-is it diagnosed yet? Since it starts then dies I’d go back to basics (fuel, spark, sensor codes):
1) with the key turned to the run position (not start) does the fuel pump run about 3 seconds? It’s normal for it to time out if you don’t start it. But the question we’re trying to answer is does the PCM send power to the fuel pump relay when the ignition is in run.
2) what is the fuel pressure? On my 98 the spec is 49psi-I think 2000 is the same.
3) after 1) does the fuel system hold pressure? Shouldn’t lose more than about 10psi in 20 mins. So, is there a fuel escape path that’s bleeding down fuel pressure (stuck open injector)? Ideally have a helper watch a fuel pressure test gauge at the rail as you start, run, die to see if the pressure drops.
4) on a 2000, is it one ignition coil or 6 coils (coil in spark)? If 1 coil it’s easy to check if there is voltage to the coil with the key on run? If 6 coils can you check this on one or more?
5) Is the PCM storing codes? Even if the check engine light is off, the PCM may have “pending codes”. If you have a bad sensor (crank position, throttle position, cam position, etc) there may be pending codes that aren’t stored codes yet.

I hope this helps or you’ve solved it already,
TJBUD

Re: Start then dies

Posted: May 31st, 2023, 4:19 am
by MilehighGS
Thanks TJ!
The pump does prime with key on, for a few seconds. There is steady pressure at the rails with no drop. I have plugged a scanner on it for ant codes and nothing.
Do all 2000's have a chip key? I'm questioning the key I am using to start it up with. It is a newer cut key my son had.

Re: Start then dies

Posted: May 31st, 2023, 11:22 am
by amcinstaller
I forget exactly which light it is in that year but chrysler had a few different security lights in that Era,
- small round inscription red light
- red light up high by the windshield
- yellow picture of a key with a circle and crossing it out in the cluster

Generally if the key is the issue, the light will be flashing

Re: Start then dies

Posted: May 31st, 2023, 11:34 pm
by Cheromaniac
If it had been an anti-theft system security key issue, the engine wouldn't even crank.
Have you checked the crank and cam position sensors?

Re: Start then dies

Posted: June 2nd, 2023, 5:14 am
by MilehighGS
Cheromaniac wrote: May 31st, 2023, 11:34 pm If it had been an anti-theft system security key issue, the engine wouldn't even crank.
Have you checked the crank and cam position sensors?
Has new crank sensor, installing cam sensor tonight.........fingers crossed!

Re: Start then dies

Posted: June 4th, 2023, 8:12 am
by MilehighGS
New cam sensor did nothing.........

Re: Start then dies

Posted: June 5th, 2023, 5:55 am
by Cheromaniac
This might help you troubleshoot the issue:

https://mechanicbase.com/driving/car-st ... uel%20pump.