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Old July 8th, 2012, 11:27 PM   #1
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Default 95 YJ 2.5L fuel relay issue, need help

My weakest mechanical ability is with electrical things. Here's my issue.

On my 95 YJ with a 2.5L I'm having issues with the fuel pump turning on. Sometimes, it works fine, other times, I cycle the key and it doesn't turn on/prime. In the cases when it doesn't turn on, if I do NOT try to start it, but instead let it sit for a 15-20 seconds, the relay will start rapidly clicking, maybe 15 times over the course of a few seconds and then the pump will prime. For the next few key cycles, the pump will prime every time until the jeep sits for a while, then the issues happens again.

Here's some other info.
- The pump is new and it's wired correctly, I replaced it thinking it was the issue.
- The relay is not new, but I switched it out with another relay and the issue seems to be the same. I may go buy another relay just for shits and giggles. I suppose it can't hurt to have an extra anyway if that turns out to not be the issue.

I'm thinking poor ground or perhaps a weak power input. Not 100% sure how to check for that on a relay. Any help would be appreciated on how to test and open to suggestions for other issues!

Thanks,
Matt
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Old July 10th, 2012, 09:26 AM   #2
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No one huh...
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Old July 10th, 2012, 12:34 PM   #3
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Quote:
Originally Posted by sodapop View Post
I'm thinking poor ground or perhaps a weak power input. Not 100% sure how to check for that on a relay. Any help would be appreciated on how to test and open to suggestions for other issues!

Thanks,
Matt
Use a test light to check power supply to the relay. If it's bright, power is good. If it's dim, then you have an issue. You can also use it to check the relay ground. If the relay clicks with the test light connected to the ground side, you have a ground issue (you have to be quick about this because the ECM only turns on the relay for a few seconds with the key on).
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Old July 10th, 2012, 02:06 PM   #4
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Or possibly the driver in the ecm could be going bad? I'd lean toward dirty wiring somewhere though.
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Old July 17th, 2012, 12:19 PM   #5
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Default ECM Capacitors were failing

After some significant researching it turned out to be a failing ECM. More specifically it was the Electrolytic Capacitors in the ECM failing.

I found this write up on Jeepforum.com and followed it to do the repair.

http://www.jeepforum.com/forum/f12/c...rs-ecu-492597/

Just for the sake of not having to follow the link, here's the text from their page.

PLEASE NOTE: I did not create this or find this fix. I was just lucky enough to find the link. All the credit for the repair and the pics goes to sasquachYJ over at Jeepforum.com

This is for a '94 Yj 2.5 liter ECU repair,
Symptoms: turn key but no check engine light but after a few minutes of the key on, you hear clicking and then the check engine/shift light come on and you hear the fuel pump prime and it starts right up.

-I've been dealing with this for about 3 weeks now since the weather has gotten cold. when the problem first arose I thought it was a bad fuel pump so I replaced it and the strainer still same problem. I was really getting fed up with the problem of leaving it and coming back and having to wait 5 minutes before it would start, i searched all over jeepforum for an answer i found sentinel02's thread about checking all the plugs leading to the ECU very complex but informative but i didnt feel like checking all the electrical components. so I either had to send my ECU out to get rebuilt or rebuild it myself so I decided to take it step by step to show in detail how its done, due to the fact that i havn't seen a step by step version of this and also I noticed lots of '94 YJ owners having the same problem.

Tools/Equipment:
Small needle nose plyers
Soldering gun(including flux, wire)
x3 220 uf 35wvdc capacitor (radio shack) the stock spec is 25v but 35 seemed to work also.
utility knife
silicon/sealer
8mm socket

STEPS:
1. take ECU out of Jeep you'll need to remove the washer fluid container held on by one philips screw on the side and then it just slides right out.

2.now for taking off the ECU disconnect the main wiring harness leading into it using a 8mm socket, when loosen bolt and pull off gently being sure not so break any contacts.

3. once the harness is off there are 3,8mm bolts just undo them and the ECU will pop right off the firewall.

4.Take the cover off by prying at the prongs that hold the lid to the casing.

5.once cover is removed run a utility knife along the edge close too the plastic once you have cut alll the way around gently pull the ECU itself out of the casing.

6. now heres were it gets tricky. locate the 3 capacitors on the top of the ECU
http://i259.photobucket.com/albums/h...l/S7301732.jpg

7. After locating them you have to dig out on the underside of the ECU to expose the ballistics encased circuit board. Its a tidious task but it has to be done to get the capacitors out.
http://i259.photobucket.com/albums/h...l/S7301729.jpg

8. now that the contacts are exposed take a soldering gun and melt away the factory solder points, have a friend grab the contact on the top side and pull as you melt the solder.
http://i259.photobucket.com/albums/h...l/S7301731.jpg

9.After you get them out take the gun and put it were the contacts went through to make a hole for the new capacitors to go through.

10. now its time to put the capacitors in, make sure that the side with the stripe is facing the big metal tower (reference picture)
http://i259.photobucket.com/albums/h...l/S7301732.jpg

11.push them all the done and solder them on the other side back in the original place making sure the stripe is facing the correct way.
http://i259.photobucket.com/albums/h...l/S7301734.jpg

12. once they are soldered in place take nailclippers and clip the extra wire.

13. take putty or silicon to reseal the holes wait for it to dry and follow the take out procedure in reverse order.
http://i259.photobucket.com/albums/h...l/S7301740.jpg
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Old July 17th, 2012, 12:26 PM   #6
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I followed the repair and the jeep runs perfect again. I used the radio shack capacitors that he suggested (220 uf 35wvdc capacitor) without issue. The total cost was as listed below:

220 uf 35wvdc capacitor X 3: $1.49 per capacitor so $4.47
Spool of solder was $8.79
Tube of silicon $6.99
Total was $20.25 + tax = $21.47
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Old January 5th, 2014, 03:06 PM   #7
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a BIG thank you to sodapop for the link. worked like a charm. props for the share and the credit placed where it was due.
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