Today I followed the instructions to replace the capacitors and my jeep starts immediately every time. It was easy and I thank you for the savings of hundred of dollars. I do have a new issue which came with this fix. Now the check engine light comes on when I turn the key, the fuel pump kicks on and the engine starts right up. However the check engine light does not turn off. The fuel pump does not stay on if I turn he key but don't start the engine. Also now I don't have high beams. When I turn them on the dash indicator shows high beam but the lights kick out?
That is bad news if it is right you should absolutely not start it until you have a meter. The alternator is full fielded and putting out enough voltage to cause the battery to boil and explode. This is no joke. You need to see if it is accurate by measuring the voltage at the battery with a meter. If it is correct then you need to see off the pin for the alternator control at the ecu is shorted to ground. Post back.
I did start the jeep to see what kind of drop I would get with lights and blower. It ran for about 30 seconds and I then looked at the battery to make sure all the connections where tight. I could hear the battery starting to boil. Can you help me locate the pin at the ECU and what to look for. Something definitely unsafe here.
I want to add my thanks to the countless others who have done the capacitor change on the ECM. This was an amazing fix and so simple it was scary. I kept second guessing myself because nothing ever goes that smooth when working on a jeep! Lol. Thank you for saving me hundreds of dollars!
Excellent write up. Had to do this to my jeep recently, and I found it really helpful.
I just wanted to drop in my $0.02 about the capacitors. From what I read on the internet the brand that Radio Shack sells isn't really known for producing capacitors with quality electrolyte. The brand sold by Radio Shack is Lelon. The other problem with the caps sold there is that they are rated at 85 degrees C., whereas the ones that were installed from the factory are 105 degree C caps.
So I went a little further, and researched good brands of capacitors. What I came up with is a brand called Rubycon, and you can regularly find them on Ebay (from American Sellers) by searching Rubycon 25V 220uf High Temp Capacitor.
Just wanted to chime in here, of course I am sure the ones from Radio Shack work, but if the goal is to not have to replace them again at some point, it might pay to have this info regarding replacement options.
I thank the author for the great fix. I just ran this process on my son's 94 yj manual 4.0, starting is nearly instant now, smoother running and the extreme tach flutter is gone. 3 220uf caps removed and replaced. fyi, my local radio shacks didn't have enough, but there was a bag o' 20 caps for about 5 bucks that had 4 of them
MM2/SS USN; CM1/SS USNR
Stop and smell the Mud.
2003 RHD 4.0 TJ postal / 1997 4.0 YJ (son's)
My jeep starts fine, the CEL comes on and turns off, no codes are being thrown, I haven't listened for the fuel pump. Ran fine when I bought it last summer and now with this extremely cold weather we've been having in upstate NY it's having problems. When it starts and I let it warm up on cold mornings, the idle gets so low and choked out that it seems like its about to stall then vroom, kicks back up to normal, then happens again, etc etc. When I start driving it'll choke out and then vroom gets going again (i've noticed it's usually in low RPMS) or I clutch it and it stops. This happens for about the first 5 minutes of driving then it goes away. Am I catching this capacitor problem before it really becomes worse and won't start or is it something totally different?
POst up to a new thread with your problem and we can try and help you through it. This thread is for the ecu issue and we should try and keep post related to the ecu. PM me when you start a new thread.