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Old 12-02-2019, 03:30 PM
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no power to coil

Been having an issue for a few months. Parked jeep, went inside, came back out and it cranks but no start. I was able to determine there was no spark from the coil. Replaced the coil and it started so i assumed that was the issue. But when driving it would sometimes just randomly stall... Then it would not get spark again, id go mess with the coil and it would fire up... so it has been an intermittent issue for a while now.

A few days ago i was parkled at my garage, went to leave and had no spark again. I started messing with the coil, but nothing changed. I had a spark plug in the end of the coil wire that goes to distributor laying on the block, key was in the on position and i was using a screwdriver to jump the starter and look for spark... well i messed with the connector that goes to the coil, and i started getting sparking. some sparking from the wires themselves (behind the alternator area) and i was getting a lot of arcing from the threaded part of the spark plug when it touched the block...

Currently, i have a new distributor cap and rotor as well as a new pickup. I am not getting power to either of the wires going to the coil (drkgreen/orange and grey) Also no power at injectors green/orange wires. I tested with a multi meter with neg probe clipped to - terminal on battery and positive probe on the wires with the key in the on position.

alternator is getting power. but there is no power to the green/orange wire that leaves the alernator.

auto shutdown relay clicks loudly when key turned, so I don't think its bad.

on the wiring diagram it looks like the green/orange wire just goes from the coil to the injectors, the alternator, the ASR, then to the o2 sensors. it crosses a white/orange wire that goes directly to the PCM (powertrain control module)

the grey wire goes directly to the PCM

Any help would be greatly appreciated. i attached a copy of the wiring diagram

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Old 12-02-2019, 03:53 PM   #2
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Old 12-02-2019, 07:07 PM   #3
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Welcome to the Forum shawnk111,

If we knew what year your Jeep is and what engine you have, it'll be easier to figure out how to help you.
If I understand your post, it seems like you might have frayed wires somewhere, either in a connector or in a loom. That's where I'd start looking.

Good Luck, L.M.
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Old 12-02-2019, 07:30 PM
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Sorry I should have mentioned it's a 94 .... 4.0.... I checked over the wiring and everything is in tact. I removed tge connector that goes to the pcm and cleaned it and put some dielectric grease, but it was I good shape
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Old 12-02-2019, 08:02 PM   #5
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Quote:
Originally Posted by shawnk111 View Post
auto shutdown relay clicks loudly when key turned, so I don't think its bad.
Don't assume that is true. I have seen relays that click but are not good. It just means the control side of the relay is probably good.

Swap the relay with another in the PDC and see if that works. Based on the fact that other parts, O2 heaters, injectors are not working, sure seems like power is not coming from the ASD.

If the swap-tronics doesn't work, then we can walk you through troubleshooting the relay socket. Make sure it has what it needs to work.
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Old 12-02-2019, 09:21 PM
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great thanks ill try that tomorrow morning
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Old 12-03-2019, 10:28 AM
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Okay switching the relay with other ones I not change anything. With the key in the on position, I get 0.02v to the green/orange wire and I get 0.03v to the grey wire.
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Old 12-03-2019, 02:09 PM   #8
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Do you get battery positive for at least 3 seconds before it goes to 0v?
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Old 12-03-2019, 02:24 PM   #9
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Here is how I'd test the ASD relay socket. It's a good place to do some testing because it a spot where several circuits come together in a convenient spot. The results can give you a good direction to go.

The ASD relay has the following connections:

Pin 30, red/white: Power comes from fuse 1, 30A. Hot at all times.
Pin 85, Dark Blue/yellow: Goes to PCM. Computer applies ground to this when it wants to run and start.
Pin 86, White/yellow: Comes from fuse 5, 10A. The fuse gets power from the ignition switch in run/start. I think this fuse is fuse block on the inside. Hot in run and start.
Pin 87, Dark Green/orange: This is power from the relay fed to the ignition coil, generator, injectors, O2 heaters and a signal to the PCM that it is on.

Note that when I say pin 30, 85, 86, 87 I am referring to the standard relay pins not the pin out on the PDC. Usually the numbers are on the bottom of the relay. You just need to map them to the relay socket.


Here is how I would test it.

For the ASD relay, use a test light and multimeter...here is how.

Load side
Pin 30 , this is hot at all times. We can test this by taking a test light. Clamp it to battery negative and touch the 30 pin in the relay socket. DO NOT stuff it in and spread the pins. Does the test light light?

Pin 87 . This is wire should go injectors, 02 sensor heater wires and ignition coil. Your best test here is probably with a multimeter. If you connect one lead to battery positive and one to pin 87, it should show battery voltage. This just indicates there is a path to ground. Probably the best test to do now without going to more extreme measures. Or a continuity check from this pin to power side on the ignition coil harness.


Control side
Pin 86. This comes from the ignition switch. Take a test light. Connect the clamp to ground or battery negative. Touch the tip of the test light to pin 86. Have someone turn the key to start and run. The light should run in both positions. And be off with the key off.

Pin 85 . This is the ground or negative side of the relay coil. Take a test light. Connect it to battery positive. Touch test light tip to pin 85. Turn the ignition switch to on. The light should light for when the computer commands the ASD on. Test light should turn on when you turn the key to start and in run.

Note, my pin 85/86 may be reversed. You can do the test with either and not mess anything up. But they are both part of the control side of the relay (the electromagnet side).

Make sense? Report back with your findings.
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Old 12-07-2019, 03:36 PM   #10
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Do you do anymore testing?
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Old 12-08-2019, 10:12 AM
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No unfortunately I haven't had time yet. Been working on other customers vehicles. I was working on a Dodge ram and found it has the same ignition setup. I tested the green/orange wire and found that it is actually a ground... So that's new info for me. I will do more testing hopefully tomorrow and post back. Thanks again
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Old 12-08-2019, 05:03 PM   #12
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Find a post by Got it at last. In his signature there's a free link to several Factory Service manuals and a couple Factory Parts Manuals.
Open that link and click on the manual that you need.


Sorry, I should have posted this sooner. I thought I already had.

The schematics usually are in the electrical troubleshooting section.

Good Luck, L.M.
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Old 12-08-2019, 11:26 PM   #13
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I delt with the same random issue for awhile in a 93 4.0. Finely tracked it down to the ignition switch at the top of the steering column. 400,000 miles on the odometer, it was original equipment, I am the original owner.

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