Jeep Cherokee:

94 cherokee cranks but no spark

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# 1  10/8/2016 12:31 AM

Veltri77
New member
Registered: 10/8/2016
Posts: 7

94 cherokee cranks but no spark

I have a 94 manual 4.0l cherokee.  I shut it off the other day and then no spark. I have narrowed it down to no 8volt supply from the pcm. I just don't know why. After disconnecting the speed sensor, distributer, and crank position sensor, still no 8volt supply. Continuity through the circuit. Not grounded out. I even tried my pcm in another cherokee and it worked fine. I'm at a loss. Any suggestions?

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# 2  10/8/2016 3:06 PM

TechHelp2
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Registered: 11/24/2009
Posts: 1299

Re: 94 cherokee cranks but no spark

I have a wire schematic for the PCM on your vehicle and it appears to show the 8 volts coming from the camshaft sensor. I have the schematic from the Alldata automotive information website below.

https://www.realworldautomotive.com/forums/uploads/thumbs/174_42144704.gif


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# 3  10/8/2016 3:28 PM

Veltri77
New member
Registered: 10/8/2016
Posts: 7

Re: 94 cherokee cranks but no spark

I replaced coil and after a code p0335 the crank position sensor. The 8 volts comes from the pcm. I'm not getting it even after unplugging the crank, came, and speed sensor. Thought it might be grounded somewhere but it isn't.

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# 4  10/8/2016 5:05 PM

TechHelp2
Administrator
Registered: 11/24/2009
Posts: 1299

Re: 94 cherokee cranks but no spark

I would check for the 8 volts at the pcm and trace the wires to the crank shaft sensor for an open or short. I listed trouble trees to your vehicle to help you diagnosis the problem. The Jeep has been known to have bad crank sensors, if all checks out it may still be possible to have a bad crank sensor.

https://www.realworldautomotive.com/forums/uploads/thumbs/174_41798722.gif

https://www.realworldautomotive.com/forums/uploads/thumbs/174_62486840.gif

https://www.realworldautomotive.com/forums/uploads/thumbs/174_179639528.gif

https://www.realworldautomotive.com/forums/uploads/thumbs/174_155557632.gif

Images from Alldata information website.


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# 5  10/8/2016 5:28 PM

Veltri77
New member
Registered: 10/8/2016
Posts: 7

Re: 94 cherokee cranks but no spark

I have gone through that whole book. I have the schematic too. It's not shorted. Has continuity from pcm through all three cam,crank,speed sensor. Something is telling the pcm to not supply the 8 volts. I just don't know what it could be

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# 6  10/10/2016 3:05 PM

TechHelp2
Administrator
Registered: 11/24/2009
Posts: 1299

Re: 94 cherokee cranks but no spark

Does your Jeep have a security system?

I did some research on this and if you use the remote to unlock the door, lock the door then unlock the door this resets the system. See if this changes things.

If the remotes don't work then  turn the key on then go to the passenger door and lock and unlock the door three times.

Some security systems shut down the fuel infectors and some do the ignition system. I can't find any information on your system.

It's worth a shot.

I am also confused but am still looking. I am asking the administrator for more information.


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# 7  10/10/2016 4:20 PM

Veltri77
New member
Registered: 10/8/2016
Posts: 7

Re: 94 cherokee cranks but no spark

When I saw that I was hoping that was it too. But mine does not have electric locks. The only wires going into the door is speaker wires. I do have the wires off the pcm that go to ccd + and ccd -

I don't know where they go from there though.
I have also tracked down the asd circuit. It all works except while cranking it over I only get 7 volts to the coil but if I use my scan tool and actuate the asd relay I get 12. My Chrysler book says I'm supposed to have 10 volts on that circuit but I have 12. Not sure why but even after jumping the relay it still has no affect on my 8 volts side of the cps.

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# 8  10/10/2016 6:19 PM

Administrator
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Registered: 9/27/2008
Posts: 1279

Re: 94 cherokee cranks but no spark

The ASD relay does not supply voltage to Crank, Cam, or VSS.

Have you confirmed the 8 volts not coming from the PCM by back probing terminal 7 with the ignition on?

If no voltage there, confirm battery and ignition 12 volts going into the PCM at terminals 3 and 9.

Also confirm good grounds at terminals 11, 12, and 5,


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# 9  10/12/2016 10:36 PM

Veltri77
New member
Registered: 10/8/2016
Posts: 7

Re: 94 cherokee cranks but no spark

No voltage pin 7. Yes 3,9. All grounds are good.
Finally took it to the shop. They saw the same thing. Owner said it's common problem. His tech line says to put a resister and ignition 12 volts to pin 7. Bringing it down to 8 volts. They did and it fired right up. So I guess no one knows why it happens.

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# 10  10/12/2016 10:48 PM

Administrator
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Registered: 9/27/2008
Posts: 1279

Re: 94 cherokee cranks but no spark

That's kinda a "hot wire" fix. Still a fault preventing 8volts from the PCM at terminal 7. But if it works, it works...

My next suggestion would be checking the "pin fit" at terminal 7. Sometimes the female terminal in the connector get's widened preventing a good connection with the male terminal in the PCM. Should also inspect for any sign of corrosion.

Glad you got it going!


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