Jump to content

1988 4x4 Automatic MJ starts But Will Not Run?


Recommended Posts

Alright, my trucks been out of commission for around 3 weeks, and I've tried everything I can think of to fix it, all attempts coming up fruitless.

 

When you turn the key to start, it starts, and when the key goes down to the run position, it dies. If you hold it in start, itll run along with the starter cranking. It will continue to do this as many times as you want to turn the key

 

So far attempting to fix this I've tried jumping the ballast resistor, no change. I checked the ohms on the crankshaft position sensor, 198, almost perfect and easily in the functioning range. I've disconnected the starter solenoid, cleaned the contacts, and reconnected. I changed the ignition switch under the steering column, which changed nothing, ruling that out along with the keyswitch. I checked my ignition coil, its good. I brought my ignition control module to autozone, and they said it was good, though i don't see how a simple multimeter test can acurately say it it can perform all of its functions. I checked pressure in the fuel rail, and it was exactly what it was supposed to be with the key in the start and run position, which i think rules out the fuel system (correct me if I'm wrong). My air filter is good, battery is at 12.57 volts.

 

Power is going to the ignition control module, 12 volts in the yellow wire in the electrical connector with 3 wires, and around 5 volts in the yellow wire in the electrical connector with 2 wire openings, just one with a yellow wire in it. I think ithas to be either the ignition control module or the camshaft position sensor, inside the distributor. I'm 16, just bought the truck around 2 months ago, and have no idea what else to do. If anyone has any ideas about what could be wrong, please let me know. Thanks

:cheers:

Link to comment
Share on other sites

i would suggest taking of one of your plugs and see if it tries to fire once its in transition and if it does then your CPS is off. you could also try another distributor from a junkyard and see if that does the trick. also did you check to see if your fuel pump is running??

Link to comment
Share on other sites

yeah take a plug out and have it connected to the wire and have someone start it (make sure the plug is toughing metal) and then if it sparks its not your dist. if it stops right away then its your dist. either way i would either rebuild the dist or go to a junkyard or find a spare and try that. maybe try to time it(not sure if you can or not)

Link to comment
Share on other sites

no, if it runs with the key cranked to starter position, you don't have anything wrong with operating systems most likely.

 

that becomes a problem with one of your key on supply wires. there's probably a bad connector inside the cab going to the fuse box or something along those lines.

 

check all wires for burnouts, and all connectors.

Link to comment
Share on other sites

ooh just remember happened to my friends XJ 2 or 3 weeks ago. check your fuses under the hood. he blew a 30 and we took it out of the A/C i think and it works now

 

88 doesn't have the fusebox under the hood...just in the engine bay.

 

it has 3 relays there though. replace them, check all of your fuses

Link to comment
Share on other sites

ooh just remember happened to my friends XJ 2 or 3 weeks ago. check your fuses under the hood. he blew a 30 and we took it out of the A/C i think and it works now

 

88 doesn't have the fusebox under the hood...just in the CAB

 

it has 3 relays there though. replace them, check all of your fuses

 

fixed it

Link to comment
Share on other sites

well ive checked all the fuses, their all good. Ill try the transision from start to run with a plug out and see wut happens when my dad gets home since it needs 2 people and ill check all the wires in the cab for burnouts. Hopefully that solves the problem. :cheers: Poor truck just wants to run :cry:

Link to comment
Share on other sites

Yea the fuel pump is running you can hear it. Are you talking the top or bottom part of the distributor? And just start it and put it back to run with one spark plug out?

 

The fuel pump is running when you first turn the key ON? How about after you start it and release the key? Reason I ask is because in the HO's at least (ASSuME it's the same in the Renix models) there is a fuel pump relay that bypasses the ballast resistor when starting, then latches after the engine starts to put the ballast resistor back into the fuel pump power circuit, dropping the operating voltage to about 9V. If the fuel pump relay was bad you might be losing power to the pump after it starts and you release the key. Suggest checking the fuel pump voltage in all positions of the ignition key.

Link to comment
Share on other sites

Hornbrod beat me to it.

 

The ballast resistor is the grey-white ceramic block on the inside of the driver's front fender, tucked in bwtewen the air box and the fender. Two fairly heavy (12-gauge?) wires to it.

 

Just jumper the two wires together. If it stays running, that's your problem.

Link to comment
Share on other sites

Alright, i found the problem. Kinda sad that it turned out to be a bad wire next to the fuseable link, that i missed when checking it earlier. This time i pulled frmo further out, and the wire stretched out like an elastic band. I'm glad this fix ended up being so easy. Thank you guys so much for all your help, i was completely out of ideas and was about to give up if it werent for you telling me how to troubleshoot diff components. I'm so glad my jeeps finally running, this kicks @$$. jamminz.gif :USAflag:

Link to comment
Share on other sites

Alright, i found the problem. Kinda sad that it turned out to be a bad wire next to the fuseable link, that i missed when checking it earlier. This time i pulled frmo further out, and the wire stretched out like an elastic band. I'm glad this fix ended up being so easy. Thank you guys so much for all your help, i was completely out of ideas and was about to give up if it werent for you telling me how to troubleshoot diff components. I'm so glad my jeeps finally running, this kicks @$$. jamminz.gif :USAflag:

 

 

you're welcome. I had a feeling that if it ran at 1 point but not at another, you simply had a bad connection...

Link to comment
Share on other sites

  • 3 weeks later...

Thank god for the internet. my manche died on me in my buddy's yard on saturday. i had no friggin clue why. it would start, but would not stay running. checked a bunch of things, got out the wiring diagrams. changed the tps. that didn't work. was kinda discouraged (thought my fuel pump died). then i remembered seeing a post on here (prolly this one) about somebody having a similar issue. i searched, i found, i read. i then disconnected the two wires leading to the ballast and connected them with a short piece of wire. the truck fired up and stayed running. i disconnected the wire, and the truck died. beautiful! found the source of the problem. a quick trip to the boneyard, one used ballast later, problem solved.

 

thanks for the info guys.

Link to comment
Share on other sites

... a quick trip to the boneyard, one used ballast later, problem solved.

 

thanks for the info guys.

I wouldn't count on a junkyard ballast resistor. It could fail tomorrow. I was advised years ago by a friend who was a Jeep service manager that the ballast resistor is a highly unreliable part. Chrysler used to use them in their ignition systems and Mopar mechanics always carried a spare in the gove box. I always carry a spare in my Jeeps. (Although it is possible to bypass it by just jumpering the wires.)

Link to comment
Share on other sites

... a quick trip to the boneyard, one used ballast later, problem solved.

 

thanks for the info guys.

I wouldn't count on a junkyard ballast resistor. It could fail tomorrow. I was advised years ago by a friend who was a Jeep service manager that the ballast resistor is a highly unreliable part. Chrysler used to use them in their ignition systems and Mopar mechanics always carried a spare in the gove box. I always carry a spare in my Jeeps. (Although it is possible to bypass it by just jumpering the wires.)

 

and i wouldn't trust a service manager telling me used parts are junk. of course he'd say that. he's the service manager. he wants ppl to come to the dealership for everything so they can get raped on prices for parts and labour. i will now carry that piece of wire with me in the glove box. if the same thing happens again, i can use the wire to get me to the parts store.

 

oldjeep-my guess? somebody has either by-passed that resistor and connected the two wires together permanently, or they've used a different resistor (from an electronics store) and connected them that way. just a thought. you'd have to find the two wires coming out of the wiring harness and find out where they go.

Link to comment
Share on other sites

and i wouldn't trust a service manager telling me used parts are junk. of course he'd say that. he's the service manager.

Did you read the part of my post where I wrote that the guy is a "friend"? That's "friend" as in, I have known him for fifty years, my brother and I both crewed on his stock car when he was actively racing, we all belong to the same collectors' club, my brother and I have breakfast with him almost every Saturday and then spend half the day shooting the bull in his (home) garage. He's been retired from the dealership since 1988 -- he's not trying to sell me any parts. Trust him? He's one of maybe four people in this world whom I absolutely trust ... period.

 

Plus, he didn't say used parts are junk. Nobody did. I said that with used parts you have no idea how long they may last. That's a fact. You can dispute it all you want, but that's why used parts cost less than new parts. Hard parts, it doesn't make much difference. Electrical parts, especially those that are known to fail unpredictably anyway, are a real crap shoot when you buy them from a junkyard.

Link to comment
Share on other sites

Eagle-my bad. "friend" can mean a lot of things. you know, rather than saying "this guy that my sister once dated four years ago for about a month and a half" or "a guy who played a couple games on my ball team last summer", you say "friend" cuz it's just plain shorter. after reading my post, i realize i might have sounded a bit assholish in my response, but i didn't mean to. i do know that the dealership where i live are con artists ($450 for a radiator!?!?!?! :eek: ) i will replace everything with used parts until i rape and pillage every old comanche and cherokee i can find before i ever go to the dealership for anything.

 

sure, you never know how long used parts are gonna last, but like you said, that's why they're cheaper. it doens't mean they're no good. it just means they may be good for a shorter period of time than a new part.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...