4.0 engine. Where should I start? I can hear the fuel pump come on when I turn the key over. Battery voltage looks good and I cleaned up the terminals and cables. I was thinking of checking for spark. How do I do that?
94 YJ turns over but, won’t start
- Thread starter JMT
- Start date
Flyer58
YJ Enthusiast
I’m working on it for a friend. It needs some love. Right now the property is covered in jeeps!
@Flyer58 OK, I got no spark for the first two spark plugs. So, the testing says that the ignition system has a faulty component. I assume since the first two spark plugs weren’t getting any spark then probably none of them are. The spark plug wires look good. I"m looking for the stupid camshaft position sensor. Not sure how to test it. I read that you can turn the engine over manually and check it with a multimeter. Heading back to the auto parts store to borrow a fuel pressure regulator to test that. What else should I look at next? Distributor?
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Ok, I’ve got fuel pressure at the rail. Still have to check crankshaft position sensor, but I don’t know how to do that. Is there anything else I can check? Like with respect maybe to the distributor or distributor cap?
Another thing, I noticed when somebody else was turning it over that my starter was jumping all over the place down there, moving quite a bit. What’s the problem there? Or is that the problem?
Well the plugs look like they need replacing. Not sure about the CPS, but you should be able to look in the FSM and there should be a testing procedure, just like there is with the TJs.
When you stay the starter was "jumping all over the place down there", do you mean that it was loose where it connects to the bell housing?
When you stay the starter was "jumping all over the place down there", do you mean that it was loose where it connects to the bell housing?
Flyer58
YJ Enthusiast
Yes, the starter was not even tight. I could finger loosen the bolts. Of course, I tightened it back up.
Did you figure this out yet? Did you check for 12V at the plug for the coil? If you have 12V at the coil but no fire, then it’s a faulty coil. They do go bad and they will crank all day and not start when they do.
If the coil doesn’t have 12V, then the PCM isn’t providing it, likely due to a bad crank position sensor, ASD relay, etc. Most common is crank position sensor. My solution for testing that sensor is throwing a part at it. If it fixes the problem, yay. If not, keep as a spare.
Just figured it out this evening. It was the coil! Thank you! I had 12 v going in, but not coming out. Very happy to have her running like a dream again!
Carova Randy
New Member
I had this same problem with my 1992 YJ I-4. The Jeep would not turn over and I did not see the “Check Engine” light come on. I suspected initially that I might have a bad ECM. But, the cure was far easier that replacing the ECM or installing new capacitators in the ECM. Instead, the problem was a blow “IGN” 15 amp fuse in the fuse box underneath the dashboard on the driver’s side. I replaced that fuse and all was well
For what it's worth, the distributor has the Camshaft position sensor in it. Honestly, there's no good way to test either the CKPS or CPS without an oscilloscope. Something most people aren't equipped with. If you run into a similar problem in the future then and exhausted all over troubleshooting options then sometimes the best option is to throw a part at it as much as I hate doing that.
Also RE: battery and ground cables. I've had cable that looked perfect externally but when cut open they were basically a tube of corroded copper. If the maintenance history of the cables is unknown, it's usually best to just replace them and then replace them on a set schedule from there on out. I do mine every 5 years or on first purchase. Given all the sensors are on a 5V reference, even a somewhat sketchy ground can have your values all screwed up going into the computer.
Also RE: battery and ground cables. I've had cable that looked perfect externally but when cut open they were basically a tube of corroded copper. If the maintenance history of the cables is unknown, it's usually best to just replace them and then replace them on a set schedule from there on out. I do mine every 5 years or on first purchase. Given all the sensors are on a 5V reference, even a somewhat sketchy ground can have your values all screwed up going into the computer.