No power to ballast resistor or fuel pump

[8Mud]

well i got home and pulled the pcm to check it out, it smells fried. I've never smelled one before, but this one smells like fried electronics. I will hit ebay after hitting the JY tomorrow, there were a few there with my engine/trans combo, and within the correct year range that I pulled the fuel pumps from. ( i pulled 3 fuel pumps when i thought that the Fuel pump was the problem)

Has anyone ever smelled their PCM?

Did you ever try to unplug the CPS and then check if the Check engine light came on when the key is turned to run?
I've been lucky so far, I've had a shorted CPS that sucked down the 5 volt sensor circuit to around 2 volts (you can check this at the sync sensor), this caused the CEL to not come on and the check code function was dead. Unplugging the CPS returned CEL and code reading function. I have yet to burn up a PCM. Before you replace the PCM, I'd try to find out what fried it in the first place.
By the way the short in my CPS was in the two pins not mentioned in the normal ohm test.

 

[GGR]

yeah I unplugged the CPS and got no CEL. I even unplugged the SYNC sensor and still got no CEL. I took out the PCM last night and it smelled fried. The only thing I can think of that could of fried it is a remote start alarm
that I have installed. That im gonna remove now

 

[GGR]

Well I've made some progress, but still have a question
I swapped the ECU and got the fuel pump to prime and spark back, have not re installed the fuel pup yet, but will be doing so in a few minutes. My question is, I got the ECU out of a 1994 same options exept no 4WD. Will i have problems with this computer?

 

[jneary]

are the part numbers the same?

 

[GGR]

no, but they cross over to the same emmision standards from the ecudirect. site.

I'll have the fuel pump in in a minute, and i guess I'll see what happens

 

[Voluster]

Don't be so quick to blame the remote start alarm. I hear stuff like this all the time. But the truck is 16 years old and a pcm going because of the remote start would be crazy the remote start does the exactly the same thing you do when you turn the key just does it with relays instead of turning the key.

I wish you luck in finding your problem. but don't be so quick to blame the remote start.

I had buddy with almost the same problem in a 89 MJ ended up being something unplugged under the dash.


Phil

Remote start alarm installer

 

[comanche91]

Surprises no one has mentioned the Auto Shutdown Relay (ASR). I had one go bad on my 91 MJ and caused similar problems. When starting the engine the ASD relay latches and looks for the distributor to spin. If not, the ASD relay trips and cuts power to the + coil and the fuel pump. A safety thing. Of course, if the relay's bad, the engine will never start. You can test the ASD relay by running +12V from the battery directly to the coil pos terminal. This will also backfeed 12V to the fuel pump through the ASD circuit. If the pump runs, the ASD relay is bad. If not, the pump itself, fuel pump relay, or the wiring is fubar. Worth a shot.

 

[waxer]

He said he already swapped the PCM and now he gets power to the fuel pump. What does that tell you?

If it was the Auto Shutdown relay, then he would still have a no spark, no power to fuel pump condition. But he does not, he has full power now to the fuel pump and coil.

My only concern is that he got a PCM from a diff model jeep, so I'm not 100% it's the correct one.

 

[GGR]

yeah it's running now, but i think it's running a little richer than before, so i will seek out a 1991 computer to get everything back to normal. i drove it about 10 miles and didnt get a glowing cat or anything so i don't think it's too rich, but it may cause me some issues come smog season next year, so im going to keep my eyes open for the exact replacement computer. i only paid 35.00 for this one, so i may ebay it after i find the 91 computer.

i really wonder what makes them different????

Oh well It's running again so i can get to and from work without borrowing or hitching a ride.

Thanks for all the help and advise guys, but yeah waxer is right, this aint the right ECM for the job. Why...... i have no idea. it just is what it is.

 

[comanche91]

He said he already swapped the PCM and now he gets power to the fuel pump. What does that tell you?

If it was the Auto Shutdown relay, then he would still have a no spark, no power to fuel pump condition. But he does not, he has full power now to the fuel pump and coil.

My only concern is that he got a PCM from a diff model jeep, so I'm not 100% it's the correct one.

AAARG, got to learn how to read - missed that. There's got to be 20 different possible PCMs..............

 

[waxer]

yeah it's running now, but i think it's running a little richer than before, so i will seek out a 1991 computer to get everything back to normal. i drove it about 10 miles and didnt get a glowing cat or anything so i don't think it's too rich, but it may cause me some issues come smog season next year, so im going to keep my eyes open for the exact replacement computer. i only paid 35.00 for this one, so i may ebay it after i find the 91 computer.

i really wonder what makes them different????

Oh well It's running again so i can get to and from work without borrowing or hitching a ride.

Thanks for all the help and advise guys, but yeah waxer is right, this aint the right ECM for the job. Why...... i have no idea. it just is what it is.

Glad you got it up and running. Yes, once you find the correct PCM you will be golden. The PCM's are specific to the emissions components and options YOUR specific jeep came with. The PCM controls more than just the emissions. Like I said with mine, my A/C started getting cold again once I got a good PCM installed.