Hi guys. I've been pulling my hair out on my mother in laws 93 4.0 Cherokee for a week now. I'm at a loss, and figured I'd see if maybe I could score some idea's from the experts. Here's what I've got: She parked it in her garage the night before, and it was running fine. Came out the next morning and it would crank, but no start. First off it's in really good shape with no rust or corrosion issues. First thing I checked was fuel, although I can hear the pump, I checked and it has plenty of fuel. Next I checked for spark, and bingo! No spark. So next I checked the CPS and it tested fine. I later replaced it anyways and it didn't change a thing. I noticed that it powers the fuel pump relay. I next checked the fuses and the relays, and all was good. Then I checked the pick up coil, and it tested out fine. Same with the coil. I next checked to see if there was juice to the coil and while I have battery voltage with the ignition switch in the on/run position, it was only 2.90 while cranking. I'm thinking OK since the ignition module is part of the ECM, maybe that's gone bad and since the ECM powers the coil, it's gotta be that,-wrong! I've even checked to see if there's a voltage drop from the ignition switch, and it's fine as well. Am I overlooking something? I'm on chemo and am not in the greatest condition to be fooling with this to begin with. I'm trying to save her some $$$, but at this point I'm thinking I'm in way over my head........

David

 

alternator? Fuel pump? idk

 

What is the voltage at the battery while cranking? It just might be a bad battery.

 

Enough WAGs (wild a$$ guesses), if you don't know, then don't throw your hat into the ring.

 

is it cold there?? like in the mornings? mine did that before when it was cooler
try hitin the gas when you turn the key. and if itll start when you do that but dies right after it could be bad o2 sensors.

 

The battery is mid 12's, drop's to low 11's while cranking, and it cranks just fine. Temp isn't affecting it either as I checked that out after doing some research in this great forum. Lot's of great stuff to read, but so far, I haven't hit the jackpot-yet!

 

When you checked voltage at the coil, what wire or side of the coil did you measure? the simplest way to check is with a test light. put the test light across the battery paying attention to the brightness of the light, now probe the + side of the coil, it should be as bright as the batt was ( if not then your problem is there, the "asd" relay output) If that is ok, probe the negative side of the coil, you should see a pulse or flicker of the light, this indicates that the pickup coil is working to "fire" the ign coil. If both of those things work, then you need an ignition coil!
Good luck!

 

I checked the voltage at the weather-pack connector. It's same as the battery with the switch on, and it's around 2.90 or so while cranking. It does change while cranking however (varies from 2.50's to almost 4) , and the pick-up coil tested out fine (ohmed it and it changed back and forth while cranking). Even the test for power going into the distributor at the weather-pack connector was spot on at 4.99 volts. I don't remember the numbers for the coil, but it was in spec as well. I would think that 3 or so volt's just isn't enough to fire the coil. I checked the relays, and swapped them around with the fuel pump relay (same #'s) and no difference.......



David

 

You should have at least 9 volts at the coil when cranking.

 

1993 needs the CPS (in the distributer)and the CKS (at the flywheel)and the TPS to fire while cranking.
Pull the CKS sensor connector apart, check it for short circuits wire to wire and wires to ground.
Testing it for a signal is harder to do, I can provide instructions if you'd like.

 

Hi

Your king lead from the coil to the distributor is OK?

Stuart

 

how about a neutral safety switch?

 

Well, I finally found it! I had a good friend come over to see if I had over-looked something. When he checked the coil, it was shorted! I had checked it twice before and it was fine! We threw a new one on in it's place a voila! I now have proof I'm losing my mind! Anyways, I wish to thank you guys for your help and suggestions. At least I know that if she has any more problems, I know where I can come for advice!

Also a quick question if I may. A friend of a friend has a late 80's Cherokee with a 2.8 and a 5speed with a bad input shaft. On the outside it looks OK, I haven't looked at it up close, but was wondering if I would be much better off with the 4.0? What model of tranny do they use?