Ignition issue 2.5L - JeepForum.com
 
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post #1 of 9 Old 09-02-2017, 07:42 PM Thread Starter
MaxxTJ
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1997 TJ Wrangler 
 
Join Date: Sep 2015
Location: Fort lauderdale
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Ignition issue 2.5L

Hello everyone!

Been browsing the forums but having a hard time finding an answer for this one.

My 97 TJ 2.5L has been sitting for a month or so, no original issues.
But now I am trying to troubleshoot a starting issue.
The motor turns over no problem, but will not ignite.
I have checked for spark and found nothing, after replacing a large amount of the ignition system (after 100k miles never been done) I have removed the coil wiring.
I dont appear to have any power on the white wire that feeds the coil, form my understanding I should have a continuous 12v signal from the white wire to ground, this is non-existent.

I have gone through my copy of the FSM and found the wiring diagrams to show from the fuse box fuse no 6 to Automatic Shutoff Relay through 2 splices and into the 12v side of the coil. When I Ohm this out however, I dont find a direct connection from the contact side of the relay to the coil.
Am I reading this thing wrong, or missing something else?
I checked fuse number 6 (30amp) and the shutdown relay and contacts, both of these function as normal, and I get 12v on the contacts when switched, also tried to jump the contact.
According to FSM, this is what the circuit simplified looks like:

ASR->S101(splice)->C103(plug)->S128(splice)->C152(ignition coil plug)


Hoping someone here can help out, thanks in advance!

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post #2 of 9 Old 09-03-2017, 10:28 PM
mukluk
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The circuit as you described is correct. Power will come from fuse 6 in the PDC, go through the ASD when it's energised, then onward through S101, C103, S128, and into pin 2 of C152. The PCM will switch the ground wire in terminal C152 on and off during engine operation to control the coil. The catch is the ASD will only energise for about two seconds when the ignition is first switched ON then kick back off. It will also energise while the engine is cranking, but if the PCM doesn't see a signal from the crank position and cam position sensors within a couple seconds, the ASD will once again be shut off. To test the coil power circuit, you can pull the ASD relay and jumper the B1 to B2 terminals then check to see if you're getting 12V to terminal 2 in C152. To test the ground circuit, you'll need to check for continuity from terminal 1 of C152 to the PCM at A7. If both circuits check out, you'll need to verify the ASD relay is functioning, the relay itself isn't faulty (you should be able to swap it with the horn relay to see if it works), and that the PCM is getting a signal from both the crank and cam position sensors.

2000 TJ SE
2005 LJ Rubicon
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post #3 of 9 Old 09-04-2017, 11:00 AM
Selmec
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Any luck. I am in the same spot. Battery charger purchase today. Might but the ASD relay while out.
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post #4 of 9 Old 09-06-2017, 07:43 AM Thread Starter
MaxxTJ
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Hey guys thanks for the posts, sorry for the late replies, Hurricane prep
Anyways I have tested the ASD and i know that circuit is good.
Oddly enough my fuel pump does not appear to run while the ignition is set to ON. I get power on the relay but it does not activate the coil. Seem to be getting 11.6v while battery voltage is at 12.4
I understand there can be some voltage drop but that seems a bit high.

Should do some more troubleshooting after the weekend, but for now its Irma prep time.
Will update with findings.
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post #5 of 9 Old 09-06-2017, 11:45 AM
mukluk
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Just a recap for clarification:
- ASD terminal B1 should always have battery voltage present.
- ASD terminal B3 should have battery voltage present with the ignition in START or ON/RUN, check for corrosion or loose connections to fix your voltage drop.
- ASD terminal B2 is the output from B1 on through to the PCM
- ASD terminal B5 is the coil ground/control circuit. The PCM will switch the ground on and off depending on conditions - you will only see continuity to ground when the PCM has internally switched this closed.

The fuel pump relay operation is the same as above, just substitute the terminal numbers as follows:
- A6 is the same as B1 (constant B+)
- A8 is the same as B3 (ign switched B+)
- A7 is similar to B2 (feed to fuel pump motor)
- A10 is the same as B5 (switched ground in PCM)

2000 TJ SE
2005 LJ Rubicon
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post #6 of 9 Old 09-20-2017, 01:54 PM Thread Starter
MaxxTJ
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Location: Fort lauderdale
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First chance to come back to the Jeep today.
I did check the wiring previously and verified if everything is where it should be. Not that this was touched to start with, but verified nonetheless.

Finally hooked up a OBD scan tool and turn ignition to ON. No codes can be read of either the regular scan tool or the Bluetooth scanner I usually have plugged in. Just get a "NO LINK" message.
Does this sound like a ECU issue? Or am I jumping to conclusions here....Again, appreciate the input!
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post #7 of 9 Old 09-20-2017, 10:14 PM
mukluk
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Might be a PCM issue, might not. When you turn the ignition on, do your gauges read correctly and odometer display the mileage?

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2005 LJ Rubicon
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post #8 of 9 Old 09-22-2017, 08:46 AM Thread Starter
MaxxTJ
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Location: Fort lauderdale
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Mileage does read, along with the E-brake light. Both seatbelt and airbag lights turn off after a few seconds (as usual)
I do not get a battery readout on the cluster along with any other gauges, but I believe battery voltage only shows with the engine running?

Not being able to communicate using a code scanner along with the no-spark issue has me worried about the PCM, I could be wrong of course!
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post #9 of 9 Old 09-22-2017, 01:05 PM
mukluk
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The battery gauge should read with the engine not running and the ignition turned on. Likewise, the ASD relay should engergise and cause the fuel pump to run for a couple seconds when the ignition is first switched on. So what it sounds like is one of three things: not getting power to the PCM, the PCM grounds are bad, or the PCM is toast. Before you pull the trigger on an expensive part, make absolutely certain both battery cables are in good condition and have clean/tight connections at both ends of both cables, fuse 3 (30A) in the PDC is getting power through it, fuse 11 (10A) in the fuse block is getting power through it when the ignition is turned on, the main gang ground G105 located at the right rear of the engine block is clean/tight, and that the PCM connectors aren't damaged/loose/corroded or have loose/receding pins.

2000 TJ SE
2005 LJ Rubicon
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