No Spark No Fuel pump... engine cranks but no fire - JeepForum.com
 
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post #1 of 3 Old 08-11-2013, 04:13 PM Thread Starter
kazador61
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1994 XJ Cherokee 
 
Join Date: Aug 2013
Location: Midway City
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No Spark No Fuel pump... engine cranks but no fire

1994 Jeep Cherokee Sport 4X4
4.0 L AW-4 NP242

Was runnin' down the freeway yesterday afternoon on my way to run some rounds through my son's 80% paper weight that we just built, not a care in the world.... Engine just DIES... no cough, sneeze, or burp.



Towed the beast home, attempt to check if the Computer pitched any codes, and could not enter diagnostic mode. Tested to see if the fuel pump was working by jumpering the fuel pump relay... no joy. Checked for spark same result, nothing.

I've had this jeep for about 9 months without any major problems.

If I understand what I have read correctly it is not the neutral saftey switch, cause that would prevent the engine from cranking altogether. I could have misunderstood though.
Checked the CPS(CKS?) and the meter shows OL when measuring between the pins... so I think that could be eliminated.
Swapped the relays around to see if there might be a bad relay.
Checked fuses in the engine compartment and under the dash.

Is there any way to jumper the diagnostic connector to initiate diagnostic mode and if so, does anyone have the pin outs? I looked the wiring diagrams over and couldn't figure it out.

I'm leaning towards a possible bad PCM/ECM.

Would really appreciate any direction, suggestions, or thoughts, I'm in the process of C4 aquisition

Thanks
In advance
Steve

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post #2 of 3 Old 08-11-2013, 10:11 PM Thread Starter
kazador61
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1994 XJ Cherokee 
 
Join Date: Aug 2013
Location: Midway City
Posts: 2
Found the Problem

Found the problem... Always good to double check your work, or the work of someone else.
Rechecked the fuses in the power distribution module found blown ECU fuse.
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post #3 of 3 Old 08-12-2013, 04:59 AM
tjwalker
It's the crank sensor!
 
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1999 XJ Cherokee 
 
Join Date: Nov 2007
Location: Central Minnesota
Posts: 8,745
Quote:
Originally Posted by kazador61 View Post
Found the problem... Always good to double check your work, or the work of someone else.
Rechecked the fuses in the power distribution module found blown ECU fuse.
Good catch. But the question now is "why" did that fuse blow? Fuses usually don't blow willy-nilly. If it blows again, you're going to need to dig into it......

99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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