Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
1995 Jeep Grand Cherokee 4.0L
- Matts Auto
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7 years 7 months ago #22934
by Matts Auto
I got this jeep with a no start. I have good fuel pressure & good injector pulse & no spark from ignition coil. Tested cam & crank wave form ( appears to be good as comparing to others i have found). Tested for 12 volt power & signal to ignition coil connector (also looks good to me). So i thought bad coil. Replaced coil & still no spark from coil. Thought maybe bad new coil & tried another still nothing. am i missing something simple ? I tried attaching screen shots from my lab scope. First time posting a picture hope i did it right. Any thoughts would be appreciated. One picture is cam & crank. The other 2 are from the 2 ignition coil connector pins.
1995 Jeep Grand Cherokee 4.0L was created by Matts Auto
I got this jeep with a no start. I have good fuel pressure & good injector pulse & no spark from ignition coil. Tested cam & crank wave form ( appears to be good as comparing to others i have found). Tested for 12 volt power & signal to ignition coil connector (also looks good to me). So i thought bad coil. Replaced coil & still no spark from coil. Thought maybe bad new coil & tried another still nothing. am i missing something simple ? I tried attaching screen shots from my lab scope. First time posting a picture hope i did it right. Any thoughts would be appreciated. One picture is cam & crank. The other 2 are from the 2 ignition coil connector pins.
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- chief eaglebear
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- Ben
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7 years 7 months ago #22942
by Ben
Replied by Ben on topic Re:1995 Jeep Grand Cherokee 4.0L
With all your sensor plugged in do you have your 8 volt supply to cam and crank sensor? Ground as well? You said you had 12v to the coil so that means the asd is working . The grey and white wire is the ignition coil driver at the coil pack connect your scope to that wire and crank it to see if your pcm is trying to fire the coil. The crank and cam sensor wave form should both be hitting 8v. If you attached a waveform pic can't see it on the tapatalk app and I'll have to check the website ... here's a sample waveform
Sent from my SM-N920P using Tapatalk
Sent from my SM-N920P using Tapatalk
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- cheryl hartkorn
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- Matts Auto
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7 years 7 months ago #22959
by Matts Auto
Replied by Matts Auto on topic Re:1995 Jeep Grand Cherokee 4.0L
I rechecked myself this morning. I have good 8 volt supply to cam & crank sensors, good ground to cam & crank sensors & i believe good power & signal to coil but no spark from coil tower. I have good injector pulse & good fuel pressure also. Any ideas as to what i'm missing or overlooking ? Heres a snap shot of coil 12 volt power & signal with everything connected & cranking with coil connector back probed.
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7 years 7 months ago #22968
by Matts Auto
Replied by Matts Auto on topic Re:1995 Jeep Grand Cherokee 4.0L
yes all tests were done with everything plugged in. here are some more screen shots. the known good wave forms i found on internet seem to be around 5 volt peak for cam & crank sensors is that correct ?
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