badgerfly

I have a 94 cherokee with a 4.0,

was driving them quit, I have replaced and tested coil, cam sensor and crank sensor. along with everything else I can think of...

I have 12 volts into the coil, 7 ish coming out of the coil. but still no spark. I have tested the ECU, 5 volts going to the cam sensor. I have been scouring my chiltens manual trying to come up with ideas.. Please Help!!

Any ideas would be very much appriciated

Cherryokee

Check engine block to body and engine block to battery electrical grounds.
Cap, rotor, wires and plugs all good? Does your year have an ASD relay? What about fuses and/or fusible links?

Chilton's are fine in the general sense but a Factory Support Manual is your best friend at times like these...

badgerfly

All Grounds checked, wires cap and rotor are new, really struggling here...

Radi

How are you checking for spark?

badgerfly

Arcing a plug. any suggestions.

Rady, I have been reading other posts you have offfered help with I have tried many things, but I am not getting any where...

Radi

The PCM triggers the coil by grounding the (-) coil terminal. Every time that (-) terminal is grounded the coil should generate another spark.
It seems you have that happening if you measure 6-7 volts at the (-) coil terminal and +12volts at the (+), but perhaps not.

I'd check for the trigger signal itself right at the connector with the coil disconnected.
See drawing- Exploded view of the coil connector- the "K19" terminal 18BK/GY is the connection to the PCM coil driver.
I'd measure voltage at that point while cranking the engine .
Since it's purpose is to sink current, not supply it, check it by placing the + test lead for your meter on battery +, and the - test lead on the connector terminal.
You should see 6-7 volts while cranking. If it sits at zero or +12, the PCM is not trying to fire the coil.

Also- the PCM must be properly grounded for it to trigger the ignition. In case you haven't cleaned/refreshed grounds- now may be an appropriate time.

Also note there is another dark grey connector on the right fender shield the coil trigger signal passes through. Hopefully it is clean and making a good connection.

Radi

Why I didn't ask this before I don't know...but out of curiosity, when you changed plug wires, did you also replace the high voltage wire from the coil to the cap?

badgerfly

I will check these out, work getting in my way today.

Thank you for the info Radi. very helpful

badgerfly

tested the trigger signal, only getting .7 volts steady at the K19 plug...where to next??

thanks again for the help...

ambers96xj

im having the same problem....good luck

Radi

That 0.7 is while cranking the engine?

There was another thread here not long ago where a member had the same problem, and the same low reading you mention above. In his case replacing the PCM fixed it.
I'm hesitant to suggest you just jump in and buy a new PCM because they are not cheap, suggesting solutions sight unseen is always a gamble ...and in this case I'm gambling with your money.

If you are confident the sensors are all functioning (crank in particular), that the wiring, connectors, grounds and such are not the problem, then that's about all that's left.
If not 100% certain nothing has been overlooked it may be worth paying a diagnostic fee to a Jeep dealer or trusted local mechanic to confirm before spending the money.

freegdr

First thing should of been checked for codes thats why this there. Then all fuses checked. Has turning of distributor been verified ?