94 XJ, 4.0, auto trans.
while driving my jeep died. got it towed back to my house. i have no fuel and no spark. looking for trouble codes, but my check engine light just stays on. i have tried cycling the a/c, and shifting through the gears as was suggested by another thread. my gut instinct tells me that my computer is shot. now here is the brilliant part- my battery recently died, and i put a deep cycle rv battery in there to get by for a couple days. did i fry something somehow? input appreciated.

 

to pull codes on a 94 do the key dance. now remember, dont start it, just click the key like this;

ON-OFF-ON-OFF-ON. the check engine light will start flashing. a long pause after a flash means its done that digit. for example, for code 43 it would be;

flash-flash-flash-flash-------flash-flash-flash.

i doubt it is the comp. if you fried something, it would be the fuses first. check them. what voltage is the deep cycle rv battery?

how do you know you have no fuel?

how do you know you have no spark?

 

The key dance doesn't seem to work. Instead of flashing, the check engine light stays on. I checked for fuel at the shraeder valve on the fuel rail. There was none present. I checked for spark on one the plug wires. There was no arc to the spark plug.

 

Deep cycle battery voltage is 12.

 

I also checked all fuses in the engine bay. They were good.

 

What about the fuses inside the jeep? Had a friend with a mis-labeled fuse ruin his wheeling trip

 

Just checked all fuses again, visually and with ohmmeter. All are good. Where is the obd1 plug? I have loooked at drivers left and right knee, I don't see them. I would like to try the shorting method. Maybe that would give me some codes.

 

sounds like a CPS to me..

 

It wouldn't suprise me. But I have replaced the cps a couple times before, the last time about 6 months ago. This time, I have no fuel in adittion to no spark, and cannot get any codes from comp. In the past, I have not had any problems retrieving those codes.

 

"""""""""Deep cycle battery voltage is 12. """"""""

Shows it's not charged. Even dead it will read 12. Measure it with key on, then measure trying to start. Cranking it has to be at least 9 volts.

Put a charger on it.

 

the jumping method only works on the v6 i believe. and the obd1 port should be on the passenger side of the engine bay, by the firewall. it has been a long time since i have had anything besides a renix.

im thinking when the battery is under any load that it doesnt turn the computer on, pressurize the pump, etc.

if the computer doesnt turn on, you wont get any codes

 

I will verify that there is voltage to the computer. Thanks for your help so far guys.

 

Ok. I admit that I am a jack***. Somehow, I checked all fuses twice, but just found one that was fried. "Engine control 2". A 30 amp big fuse. In the engine bay. Replaced it. And it blew. Tried again(cause I am desperate) and it blew again. Suggestions?

 

I guess it might be worthwhile to tell you that the fuse blew with the ignition OFF. I read 0 ohms between the terminals.

 

With the cpu disconnected I still read 0 ohms at the engine control terminals.