91+ Hard or No Start/Long cranks in the cold explained - Page 3 - JeepForum.com
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post #31 of 65 Old 11-11-2009, 09:05 PM
reddogg
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thanks for the great info. changed the caps and it fired up fine.

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post #32 of 65 Old 12-13-2009, 11:33 AM
willyb8
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ok i did it today, first i tried to start the heep. 28 deg. crank,crank, no start or cel. put blow dryer on ecu for 10min. turned key cel came on and it started. so i figured it was this ecu problem. went to radio shack spent 4.50 and dug in. first off i have the 4.0L and the caps are in different spots than the other pics but they are the only 3 big ones on board. truthfully the hardest part was removing the old silicone. couldn't figure out the polarity by looking at teh caps so i went with the putting stripes the way they were on old ones and that seemed to work. took about 45min from removal to final silicone. tested it before i put final silicone on and it stared right up. then i realized it was warmed up from doing it in the house so the real test will be tonite or tomm morn.






91 YJ 4.0 HO,
3.5" BDS, 5/8 MORE Booms, 1" BL, MML
AA SYE & CV,
35" Maxxis Bighorn
Smittybilt XRC8 Winch,
8.8 W/Elocker, D30 W/Aussie
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post #33 of 65 Old 07-31-2010, 09:37 AM
Beefalobart
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Can anyone tell me the value of the Capacitors for the 4.0 I have a 93. From what I have seen I think they are .220uf 25v but since my Jeep is at a shop almost an hour from here I cannot easily drive there to get the cap size then drive back to a main town and find caps on a saturday then drive back to replace them. I live in Charleton, SC and Jeeps at a shop in St Stephen (small town no radioshack) I do have a radio shack 1/4 from here so getting them shouldnt be an issue.
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post #34 of 65 Old 11-20-2010, 05:11 PM
mwcoast
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It sounds like the computers on Cherokees are the same - would the tests be the same as well?
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post #35 of 65 Old 11-21-2010, 08:31 AM
lewes2
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Wish I had seen this thread before taking my YJ to the shop.

My mechanic has been repairing Jeeps for a number of years but had never come across this hard-starting problem before. He spend quite some time first checking the fuel pump, wiring, and then the ignition switch electronics. He thought for sure that was the problem and replaced it. No-go. He then turned his attention to the computer and yep, that was the problem. He replaced it with a rebuilt and all is well! The 94 pops right over and starts. Thank god we got it fixed before winter sets in.

By the way, my mechanic charged me for only 2-hours of labor and the cost of the rebuilt computer. It's nice dealing with an honest person!

Chuck

Member of the Impact Orange Jeep Group
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post #36 of 65 Old 12-01-2010, 06:25 PM
adamandjessyj
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i may not have geico but i just saved $280 by reading this thread!

where thers a will, theres a way!
its not a just a truck, its my hobby.
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post #37 of 65 Old 01-10-2011, 11:01 PM
Sykora171
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PCM is changed and my '94 ZJ starts better than it ever has even in this 13 degree pittsburgh weather! before i changed it it would take up to 20 minutes at the worst for the CEL to come on. Glad she's running smooth!
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post #38 of 65 Old 02-01-2011, 02:48 PM
TapRackFire
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94 Wrangler, 4.0, no spark, no fuel, no CEL, relays clicking

Great info on the ECM repair. My 94 Wrangler, 4.0 is doing the same thing. Roll the key to run, no CEL, wait a few minutes or longer and then the ASD and the fuel pump relays start clicking. Sometimes they click slowly and sometime they click really fast. When the relays start clicking, the CEL will start to faintly flash on and off but very quickly. When the CEL would finally come on I could sometimes get spark at the coil and get it to fire when I used a fuel source (I found out later the fuel pump was bad). But I can not get a spark anymore.

I noticed yesterday (very cold outside) when the relays were clicking slowly, they would click faster if i moved the gear shifter from park to reverse and then they would slow again when i put the shifter into neutral, then fast again if I moved the slector to D, 2, or 1. Eventually if i waited long enough, the CEL would finally come on and stay on and the relays would stop clicking. But still no spark or fuel.

I have checked the fuel and ASD relay for 12v constant and with the key in the run position. I built a jumper for the fuel pump relay and that is the only way I can get 12v back to the fuel pump. I had to replace this fuel pump b/c through my testing I discoverd the fuel pump was bad.

Based on my description, am I a good candidate for reparing the ECM?

Thanks in advance for your help.
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post #39 of 65 Old 02-01-2011, 10:25 PM
Que89YJ
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Welcome to the forum Taprackfire. Post up to a new thread for your problem and you would get a quick response. Your post gets buried by tacking it onto someone elses. I didnt catch it until I was looking for an old post. To answer your question, yes.
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post #40 of 65 Old 02-01-2011, 11:52 PM
Sykora171
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Quote:
Originally Posted by TapRackFire View Post
Great info on the ECM repair. My 94 Wrangler, 4.0 is doing the same thing. Roll the key to run, no CEL, wait a few minutes or longer and then the ASD and the fuel pump relays start clicking. Sometimes they click slowly and sometime they click really fast. When the relays start clicking, the CEL will start to faintly flash on and off but very quickly. When the CEL would finally come on I could sometimes get spark at the coil and get it to fire when I used a fuel source (I found out later the fuel pump was bad). But I can not get a spark anymore.

I noticed yesterday (very cold outside) when the relays were clicking slowly, they would click faster if i moved the gear shifter from park to reverse and then they would slow again when i put the shifter into neutral, then fast again if I moved the slector to D, 2, or 1. Eventually if i waited long enough, the CEL would finally come on and stay on and the relays would stop clicking. But still no spark or fuel.

I have checked the fuel and ASD relay for 12v constant and with the key in the run position. I built a jumper for the fuel pump relay and that is the only way I can get 12v back to the fuel pump. I had to replace this fuel pump b/c through my testing I discoverd the fuel pump was bad.

Based on my description, am I a good candidate for reparing the ECM?

Thanks in advance for your help.
Definitely! My '94 4.0L ZJ was doing that exact same thing. replaced the PCM (or ECM, same thing) and it fired right up. still running strong. even in these single digit temperatures
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post #41 of 65 Old 02-04-2011, 09:28 PM
stobob1
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Super Helpful. I am Off to Radio Shack this weekend. No more getting stuck at work. Thanks
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post #42 of 65 Old 02-05-2011, 07:59 PM
TapRackFire
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Installed the 3 new caps, put it all back together, and after a little coaxing she fired right up! Tried it several times after that and she starts every time. You guys are the best!! Now on to the master cylinder.

Tap
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post #43 of 65 Old 02-17-2011, 02:24 PM
95mudman
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so i recently replaced the caps with the 35's like this thread says and now the relays stopped clicking and the pump def kicks on however i have no spark what so ever. has this ever happened to anyone before. im about to go replace these caps again with a 35v 400 rather then the 220 like this thread says. i just find it odd that i had spark before but now i dont. help me if you can...thanks!
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post #44 of 65 Old 02-18-2011, 05:35 AM
TapRackFire
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Sorry to hear of your troubles Mudman. When I replaced my 3 caps i used the 35v 220's from Radio Shack. It fired up. I know you said you had spark before the repair and now you don't, could their be another issue? Cam sensor? Have you checked for voltage or spark at the coil? There was a post that described how to use a test light and test several components both under the dash and on the firewall. This test helped to elliminate other component issues and verify the fact the 3 caps in the ECM need to be replaced.

Tap
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post #45 of 65 Old 02-18-2011, 07:41 AM
Que89YJ
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Check for voltage at the coil and fault codes before you replace the cap. Also, does the CEL come on now?
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