myjeepisDEAD

My girlfriend drives a 1999 Cherokee (4.0L, manual trans) and it died when we were off-roading. We checked fuel and air - both fine. We narrowed it down to spark - there was none. No spark at the plugs and no spark from the coil (using spark tester).

Checked fuses - all good.

Swapped relays - all good.

Did a quick check of the wires - all seemed fine, nothing ripped, braised, or out of the ordinary.

Pulled off the distributor cap. There was a bit of moisture in there (and corrosion). We let it dry and reassembled it.

Turns out the Crankshaft Position Sensor was bad (really common). This one was actually destroyed (melted, torn up and ugly - really uncommon?). We replaced it. Still no spark from the coil.

Replaced the coil. Still no spark. Tested voltage to coil - good.

Towed the Jeep to Advance, Autozone, and a mechanic. They all narrowed it down to the ECM. Bought a new one, flashed it, and swapped it in. After that we got a weird, intermittent spark from the coil.

Swapped the old ECM back in just to see if that was actually the problem. We got the same weird, intermittent spark from the coil - must have been testing wrong before? Guess the old ECM is good, but still testing everything with the new one.

When trying to start, the car cranks fine, sounds good, but the coil sends a spark every 5-8 seconds. I'm no expert, but it seems like it should be much more often - like every second or so. I'm not sure about the strength of the spark, but it was strong enough to be extremely unpleasant going through my hand.

Thought maybe the new CPS was faulty, so replaced it again. Same intermittent spark.

Also replaced the coil again. Same intermittent spark. Thank goodness Advance has such a great return policy!

Replaced distributor cap and rotor. Should probably mention that we tried cranking with the cap off just to make sure the rotor was spinning correctly and did not necessarily align to the same position when reassembling. Would this affect timing, or does that not matter?

Right now I'm thinking it could be the pickup coil under the distributor cap (same thing as cam sensor?). Now that I think back, it would probably make sense for this to fail because there was some moisture in there. Ordered one from Advance and will swap that in tomorrow.

If that doesn't work I'm thinking it could be flywheel damage or wiring.

Another thought: I heard about a freak accident about another Cherokee that was not getting a spark, and it turned out to be an O2 sensor after testing or replacing just about everything else. It doesn't seem like this would make sense at all, but I guess the sensor was sending a faulty code (or short) that prevented ignition. On our Cherokee, part of the exhaust actually fell off RIGHT after the rear O2 sensor on our Cherokee, and I'm 99% sure the sensor got wet when we went through water. I unplugged both sensors and still got the same intermittent spark.

Any ideas? All help is very very very much appreciated. This beast has been out of commission for 3-4 weeks now!

LCFRJEEP

I would start simple, check your main negative cable and make sure it is still grounded well. If you re-assembled your distributor and did not re-align it, I was always under the assumption it would jack with your timing-mabey Im not correct on this but thats what I was told. If your O2 sensors got wet, unplugging them and then cranking would not disprove or prove anything in my mind. I would replace them as well just to be safe. If anything, I think your idea about the cam sensor is a good route to look into. If you do alot of water wheeling, I would re-attach your distributor cap and them run a thin bead of silicone around the bottom of the cap to seal it. Good Luck!!

myjeepisDEAD

Thanks for the quick response. The main ground is a bit dirty but I think the connection is fine. Regardless, I'll check it and clean it in the morning.

I just read through a ton of similar issues here and I'm leaning hardcore towards cam sensor. It makes more and more sense the more I think about it.

For the distributor, I was thinking that all timing was controlled beneath the cap, hidden away and not easily accessible. Then again, this is the first time I've ever worked on the ignition/electrical components of a car (besides replacing alternators and plugs), so I could be totally wrong. This has been QUITE the learning experience!

96Cherokee113

I vote pickup coil (AKA Camshaft Position Sensor or Stator) located under the distributor cap. You sound like you know what you're talking about so I won't try and explain it to you. Same thing happened to me, though. My CPS pooped out so I replaced it only to realize it took the pick-up coil with it. I had already screwed my distributor up removing the cap because both both snapped and one side was missing the aluminum ear it screwed into. I just went and got a junkyard distributor instead of buying a new pick-up coil and rigging the cap on. I tried at first, but the old plastic shattered because it was the dead of winter. I found that you have to pull up on the rubber plug for the electrical connection to get it out without breaking it.

captainwoot

x2 on the pick up coil

myjeepisDEAD

Changed the pickup coil and still having the same problem...

That leaves the only sensor yet to be checked as the one that goes into the oil pump, I believe. I'm not sure what this sensor does exactly... but it looks pretty dirty.

Thinking this could be a wiring issue...

lliamsdad

if im not mistaken thats your oil sending unit. wouldnt think that would cause no spark but its a jeep.
Just Expect Electrical Problems

myjeepisDEAD

Does anybody know if this thing has a Neutral Safety Switch, or is that just for automatic transmissions?

Still thinking it could be a wiring issue after replacing cap, rotor, ignition coil, crank sensor, cam sensor (pickup coil), and ECM.

myjeepisDEAD

Bump.. all help is greatly appreciated.

96Cherokee113

A shot in the dark, but check the Automatic Shutdown Relay under the hood. It should be labeled in the fusebox. You can swap it for another relay of the same type for something you don't need it to run. I think the one for the A/C is the same, but not 100% sure. Just read the numbers and match em up to see if it's the relay. There's no neutral safety switch in a manual, at least not mine. I can start mine in gear with no clutch...well jump forward a few inches.

ehudpower

Sounds like you had all the same problems i have and i am hopeing to find out it was my timeing that was off and its a ***** to get the right timeing.

96Cherokee113

Also, if you've removed the distributor and you didn't put it back in the same way it came out, you have a problem. If you did, it is improperly indexed which will cause a no-spark condition. To re-index the distributor you need to manually crank the engine over until Cylinder 1 is as Top Dead Center. Then, you can pop off the distributor cap and take out the distributor. Then you have to face the rotor pointing at Cylinder 1 (5 o'clock position) and reinstall the distributor. After that, it will be indexed correctly.

myjeepisDEAD

Thanks for the replies. I didn't actually remove the whole distributor.. I just removed the cap and cranked to see if the rotor was spinning (which it was). Would this throw off the timing?

I know about the ASD relay and swapped before replacing CPS and pickup sensor, but haven't tried it since then. I'll have to check that out.

96Cherokee113

That shouldn't throw the timing off, but you could check if it's indexed correctly by cranking the engine over manually until Cylinder 1 is at TDC. Then pop off the cap and see if the rotor is pointing towards the Cylinder 1 (5 o'clock position).

myjeepisDEAD

Is there any way the indexing could be off if I never messed with it? I didn't take the distributor off, and the rotor seems like its spinning how its supposed to so I'm assuming the distributor drive gear is fine...