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1996 4.0 will not start

X

xjrocks

NAXJA Forum User
Location
oklahoma
Before hand I have searched! I have 1996 jeep cherokee 4.0. I drove it yesterday pulled it into driveway and that where it sits! I thought it was a fuel pump issues because I was getting no fuel at all. I replaced pump and still no fuel. Yes I did check the relay and it's good. I ran a jumper to and can get the fuel pump to run but it still will not start! Any ideas?? Thanks
 
If you had used a volt meter, instead of the "throw parts at it method" you might have fixed it, and had cash to spare.

Fuse?
Ignition switch?
Bad ground?

I would check for 12 volts and a ground at the fuel pump. If you jumped the new fuel pump with just one 12 volt wire in your test, then the ground IS GOOD!



Start here, if you have not done this yet:

http://www.naxja.org/forum/showthread.php?t=101119

Which Relay did you verify to be good? ASD or fuel pump?

Bad ASD relay or ignition switch, or bad fuse to the PCM, might kill fuel and spark:

"I ran a jumper to and can get the fuel pump to run but it still will not start"
Click to expand...
 
How do you know you're not getting fuel? Did you test? Does the pump kick on when you turn the key? Listen for the hum. If it is. Move up the system.
 
joejeep92 said:
How do you know you're not getting fuel? Did you test? Does the pump kick on when you turn the key? Listen for the hum. If it is. Move up the system.
Click to expand...

Read his first post again:
I ran a jumper to and can get the fuel pump to run but it still will not start!
Click to expand...
 
That doesn't test for if your not getting fuel to the rail at all...that tests for power to the pump and he doesn't tell me whether it came on or not.
 
joejeep92 said:
That doesn't test for if your not getting fuel to the rail at all...that tests for power to the pump and he doesn't tell me whether it came on or not.
Click to expand...

Jesh, read it again: "and can get the fuel pump to run"

I assume if he is bright enough to swap a fuel pump, and jump-hot wire the fuel pump, he is bright enough to check for fuel at the test port, but? LOL
 
Ok. I have tested this and that. Im thinking ignition switch. Thank you for the article which I have read. I thought maybe it could be my cps? But I tested it and it read ok. I'm lost!
 
joejeep92 said:
Haha well if he did check for fuel the pressure numbers would be helpful in diagnosis.
Click to expand...

That is true, fuel lines can get crushed (road hazards, LOL), hose collapses on the inside, fuel filter clogs, always best to confirm proper pressure and actual fuel at the fuel rail with gauges.....

He just posted he has CPS signal, which for a 96, IIRC, means he has a PCM operating and powering the CPS (Hall effect CPS needs an power input I think? I am not 100% sure??).

Why are you thinking ignition switch now?

Could it be flooded? have you rechecked for spark? Checked all the fuses?????

Have you run an ODB-II scan?
 
I don't know for sure if it is the ignition switch. The only time I can get power to fuel pump is when I use a jumper on the relay. Even with the jumper it will not start. Im lost really..
 
It doenst have spark either. So the fuel pump won't pump without a jumper and no spark to ignite the fuel. This is why I'm at loss. I've been reading and some have said ecu and others have said ignition switch. I'm gonna talk to a mechanic on Monday. It's just frustrating since it drove with no problems and then I turn it off and that's it!
 
I would check the ASD relay, Automatic Shut Down relay first (it is some sort of disabling circuit for accidents, anto rolover????), as I think it is the only thing other than fuses and the PCM that would kill fuel and spark but not cranking. It does not sound like an ignition switch to me
 
My mechanic friend came over and brought his scanner. Found out that the obd2 port is not getting power. Again went through all fuses and relays and still good there. We are thinking that it is the PCM is bad.
 
Re-read this!!!!

Ecomike said:
I would check the ASD relay, Automatic Shut Down relay first (it is some sort of disabling circuit for accidents, anto rolover????), as I think it is the only thing other than fuses and the PCM that would kill fuel and spark but not cranking. It does not sound like an ignition switch to me
Click to expand...

Did you check fuse F-15 to the ASD relay?

Have you replaced the ASD relay with a new, or know good relay?

Either can kill power to a good PCM.

Also a bad ignition switch, or bad wire to the ignition switch that powers the PCM through the ignition can cause a dead looking PCM, so:

Test or replace, the:

ASD relay,

Fuse #F-15, 30 amp fuse

and the ignition switch

(and do a wire check at the ignition switch for loose connectors, or burnt loose wires), before even thinking about swapping the PCM!!!!

If the PCM is bad, find out why, before you replace it, ie look for short!
 
I checked the ASD relay and fuse. Even ran a jumper wire to see if that would help. Nothing at all. I still haven't ruled out the ignition switch all the way. I have power to the radio/ ac/ lights/ and starter. I have never had issues at with the ignition either. I know that means nothing tho. There is still no power getting to the obd2 port to scan. My mechanic has a tool to tell if there is a short in the line. He couldn't find any.
 
Well I gave in and bought a CPS. I disconnected the battery a couple days ago and took the PCM out thinking it was bad. Tonight I went ahead and installed the cps and it turned over and started! I have drove it all around and it feels good! What I'm confused by is I ohm'd the old cps and it didn't read much different than the old one?
 
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