I have a 93 cherokee with the 4.0l. An it had a random misfire but could never figure out why. Ive replaced and checked out almost everything except the computer and crank and cam sensor. Now it will not start at all burned up 2 ignition coils. The +12v wire (green/orange) that is supplied power from the cut out relay only has 6.4v when i physcially close the relay by hand. The fuel pump relay also will not engage when it suppose to. All wiring and connections and harness are ok. Has anybody ran into this problem were that green/orange wire is not being supplied proper power to supply the coil an injectors an a few other sensors??? Ive used power probe to supply power/ground when and where needed. Still will not start. Kinda acts like bad computer but would like some extra input before spending the money on one. Thank you for any help

 

Any other info needed just ask. I have to get this thing running.

 

What are the codes?

 

No codes at all. Only flashes to show in self check an thats it

 

So to understand this, you have 12V going into the ASD relay (did you check the incoming voltage with the relay pulled?) , but only 6.4V on the output side? Have you tried swapping the relay? Perhaps burned contacts?

 

Income voltage is 12v open relay. It drops when relay is closed. Ive replaced the relays. Contacts are good on new/old relays. The computer is also sending the output (-) to close the relays but relay will not close on its own. Ive also jumped the terminals to make sure relay coil is good. There is a problem because it wont start, but everything test/s like its ok. That were im haveg trouble figuring this out. And also why i'm thinking possible computer issue. But with it's ouput/s working as far as a meter is concerend.

 

Sounds like the cps crapped out

 

What self check flash?

 

Well... 6.4 volts is not enough to operate the relays. Either your battery supply is weak- or you have a bad connection somewhere not allowing current to be drawn, or the load after the relays has a short somewhere, pulling the voltage down.
You may have to start disconnecting things one at a time until the voltage remains high when operating the ASD. Before you do that, check the battery, cables, PDC and all related connections.

 

Ya ive went threw all of that when i was checking the wiring harness. The battery is fine. And all connections are good. Any little bit of corosion on any terminals was cleaned. The funny thing is i had a customers 99 durango do the same thing. If you jumped the relay manually it worked fine. But the relay was good it was like the computer wasn't sending enough voltage for relay to close. Changed that ecm an nothing changed. So 2 seperate vehicles and same exact problem.

 

I don't know why but my jeep decided it wanted to start and run this week. Still has a random misfire. But it also dosent want to go over 3200 RPM. Misfires really bad at that point. I no this setup timing control is controlled by the computer and is non-adj. Does anybody know why it wont go any faster then 3200 RPM? Also randomly it will feel like i hit a power band (2 stroke) an there is no special thing to make it do that. Anybody ever run into those 2 problems????

 

Ttt anybody have any ideas?