skeletonizer

1994 Jeep Grand Cherokee Limited, 4.0, 249 hard starting,fuel delivery, electrical problem?

I have done numerous searches here and on other boards andtried several of the suggestions to no avail. I am hoping someone has had this issue or maybe a Jeep tech will seethis and help.

When cold it cranks over without starting. If you continue to crank it eventuallysputters to life and you have to feather the throttle a bit to get it to idle. Once running it runs fine and will restartnormally.

When you turn the key to the on position (when cold) thefuel pump does not kick on nor does the check engine light come on. When cranking and it finally begins to startyou can hear the pump start and the check engine light comes on. Once running the light goes out as normal.

I have changed the fuel pump, fuel filter, fuel pressureregulator, and fuel pump relay. None hadany effect. I have also thoroughlycleaned the throttle body including the idle air valve. All vacuum lines are in good shape with nodetectable leaks.

I have tilted the wheel while attempting to start itthinking a possible short in the column with no effect. I have smacked the ECM (computer) with myflash light with no effect. The batteryand alternator are fairly new and test out fine. The security system seems to be functioningnormally.

It is OBD 1 so not much help there. No codes.

I am leaning toward a bad ECM (computer) but wanted to getsome more ideas before I start looking for one.

It’s a ***** because when warmed up it has zero symptoms.

Thanks in advance.

skeletonizer

Today when I went out I just turned the key on without attempting to start and left it sit that way and went about my business for 10 or so. When I checked it the check engine light was off but when I turned it over she fired right up and idled like normal immediately.
WTF?

dave1123

Sounds like weak capacitors in the PCM. If left powered up for a while, they will warm up and function. Likewise with solder cracks. They will shrink in the cold, but when warmed up, will make contact.

IMHO, the PCM is suspect.

truckerjack

Pull the PCM and have the capacitors replaced by an electrical shop unless you have experience soldering circuit boards. I had the same problem as you are having. Car now starts right and runs better. Mines a 93.
Check out this post.
http://www.jeepforum.com/forum/f12/9...lained-490788/
And this one.
http://www.jeepforum.com/forum/f12/c...rs-ecu-492597/

nycmailman

it works ...for just 5 bucks got my ecm fixed thanks guys

dave1123

Hey! Please! Teach the other guys how to search older threads to fix your problem like you did, okay?

Thanks!!

SpitFire

dah! I think this may be my issue starting when the weather get chilly/cold. I am having the exact same symptoms with my 94 Grand

dave1123

Yeah, and why is the thing you've been looking for always in the last place you look?

SpitFire

I spent hours on the forum searching for something. It figures I'm thumbing through google and it pops up lol

So This morning I turned my key to the start position and waited a few minutes (5 or so). Turned off then back to start. Jeep started with no issue. Boom, problem found. F@#$ing ECM

CherokeeHoonigan

I have the same exact zj. i will Fav. this thread just in case.

LiamLikeNeeson

I'm having a similar issue. I noticed that when I turn the key into the accessory mode I hear a 3 second long hum coming from the back (the fuel pump I presume) and after the sound stops I turn the ignition on and it starts up way more easily.