I had the EXACT same issue on my 93, The PCM needs replaced. Another forum member told me to just run a wire from the ASD ground to a near by body ground, which I did for a while with no issues, only thing is the fuel pump will not shut off while the vehicle is on. Did this till I could get a replacement. I searched all of the jeep forums and the internet and all the jeep dealerships and computer repair places looking for internal circuit diagrams and no one has them, and or refuse to give it up cause they make their money rebuilding them. Still have the PCM in my basement.

 

Cozumel, I am jealous. I need a vacation and you need help fixing your jeep! I need a little more info on whats happening and I am sure we can figure it out. You said you always get the check engine light when you turn the key? Do you hear the fuel pump prime when you turn the key too? Did you actually check for fuel and spark when the issue happens? Does it die while you are driving and just not restart or is it a no start all the time?

 

I tried grounding the pin 85 on the two asd and fuel relays but would still not start even though I could hear the fuel pump running. I did not check for spark when I tried this however.


I did use an inline spark tester to check for spark when I was cranking with a no start. I will double check and see if the pump is priming every time or not, it was not before but it was pretty regular today. Sometimes it would shut down in traffic. One of the problems with this is it is so sporadic. I was hell bent on fixing it saturday and it ran perfectly all day. tried to start it sunday and got it to run one time out of 20 attempts.

Any input is very appreciated and I will check those few things tomorrow.

Cozumel is great until you get into situations like this where parts are impossible to find and 5 different guys have allready tried to fix it with 4 paperclips a stick and an adjustable wrench.

 

If the pump is working and you are stalling you are looking at a bad crank position sensor or coil. The problem is common. Post back your observation.

 

ok, so I am definitly not getting a ground to pin 85 on the ASD most of the time. when I turn the key on and off very rarely it will light the test light. So I have test light in the hole for 85 on the asd and clipped onto the pos terminal. Interestingly I get a very faint glow from the test light when the key is off. When I turn the key on the faint glow goes away instead of lighting up.

Tried grounding the 85 pin to the neg on the battery for both the asd and fuel pump but it would not start.

I am going to test the crankshaft pos sensor again, but it was fine the first time i put an ohm meter to it.

 

Tested crank shaft pos sensor with ohm meter and it read "1" so it tested ok. Could it still be bad if it tests ok?

I am getting prime on the fuel pump every time i turn the key on unless the car goes into the diagnostic mode where the cel flashes the codes at me fom turning the key on and off three times. When it does this I get no prime.

I checked and I am getting no power to the coil.

 

When you test power to the coil you need your negative lead on the battery negative. The coil only gets ground when firing a plug. Check power at the injectors the same way. Yes the cps can still be bad. Check the coil resistance.

 

Ok so my buddy Pepe came over yesterday and helped me with being able to turn the key and me testing stuff.

I have ground to 85 when key is "on " but not cranking.

If I bypass the ASD I can get power to the coil and the pump but no signal to the coil.

I am going to try to find a crankshaft pos sensor at the two auto parts stores on the island. I will let you know if that works out.

:thumbsup:

 

I am a little confused. You say that the asd has power when you have ignition on, but not when cranking? Did you use the trick I was talking about to measure the voltage? Use the battery negative for the negative meter lead. It's easier to measure the coil or injector voltage when cranking then to measure the ground on the relay.

 

sorry for the confusion, the asd relay does not get a ground from the pcm to pin 85 once it starts cranking.

 

When you turn the key on, the ecm turns on the asd and fuel pump relays to prime the system. After like 1-2 seconds it turns them off. It will not turn them back on until it sees a signal from both the crank position sensor and the cam position sensor. Once it sees thos signals, it will turn them back on and give the engine fuel and spark.
Sounds like you may have a intermittently failing cam or crank sensor.

 

That will not drop ASD power. Please check power at the coil the way I suggested while cranking.

 

yes I tried it exactly this way, no voltage at all while cranking. I have someone that is going to mule a crankshaft pos sensor to me on monday. They are $110 here and have to be ordered in. not even a mopar replacment for that price.

 

Crank sensor won't do that. You need to check power at pins 3 and 9 on the ecu while cranking. Pull the starter relay.

 

The ASD stays pulled in with the switched ignition feed to pin 9 on the ecu when you turn the ignition on. The fuel pump cycles off after 3 seconds. Check power at the injectors when you are cranking with the ground lead on battery negative.

 

Incorrect

Fuse #5 provides switched 12v power to the coil in the ASD relay, fuel pump relay, and then continues on to provide 12v power to pin 9 in the ecm.
The ECM provides a GROUND for the coils of the ASD relay and fuel pump relay. This wire is tied together and activates both the ASD and fuel pump relays at the same time. The wires that provide the relay coils and pin 9 of the ecm with power are all spliced together in the harness, being fed by fuse #5

 

Coil power should be there. If it is dropping out then you need to figure out why. I am wondering if you are losing the switched ignition feed when cranking.

 

This may be a possibility. The mechanics have cut up a bunch of wires under the dash. When I got it the ac and wipers worked with the key off. someone had cut a switched power source and wired it so it was live all the time. I could not figure out where the other end of the wire they cut went so I tapped into the blue switched wire that came off the ignition. The jeep was allready having this problem when I got it, so I dont think my patch caused the problem.

 

Exactly why he needs to check power at the coil and the injectors both. In order for the output of the ASD to drop to the coil since he has power with ignition on the switched ignition feed that powers pin 9 and feeds the ASD control side would be dropping out. Start by checking the power to the injectors when cranking and then pin 9.

 

Ok sorry for the long hiatus, life got busy here and I was waiting for the crank position sensor which I just installed. No dice same no start. I just dropped the battery off at the "mechanics" to have him charge it up. I will check pin 9 and injectors tomorrow.

When I test pin 9 do I unplug it from the Computer? Or do I trace it back to the power distribution block and test it there?

 

Check the injector voltage then pin 9

 

Ok so here are the results.

Key on not cranking = pin 9 has constant power
cranking = no power at pin 9

for the injectors they receive 12v for a few seconds when I initially turn the key on. when cranking they have no juice until I turn the key off and they get a little blip.

 

Pin 9 is the key. You are losing switched ignition. You have an ignition wiring issue.

 

looking at my wiring diagram and power for pin 9 comes directly from the ignition switch.

So I just went and tapped into the blue wire coming from the ignition switch and it does not have power when cranking. Does this mean I need a new switch? I am thinking I can at least hotwire this temporarily to get the jeep running

 

So it has power with ignition on but not cranking?

 

If you are checking the wire at the steering column and it has power with ignition on but not when running the ignition switch has to be out of adjustment or bad.

 

that is correct power with ignition on but not cranking. I am going to hot wire it first and make sure that solves it then pull the column down to check on the switch

 

runs fine if I hotwire the switched ign wire. only needs hotwire during cranking after that it will run fine

 

Your welcome. Drinks on you next cruise stop I make in cozumel.

 

just pulled the ignition switch and bench tested it. as i slide the switch forward into the start position my blue wire terminal goes dark.

Thanks for the help boys, couldn't have done it without you!