I hate Mondays. I filled my Jeep up yesterday and it ran great. Went to start it this morning to go to work and all the fricking thing will do is crank. The battery sounds strong but the engine acts like its not getting a spark. I didn’t have a lot of time and was not dressed to mess with it so I didn’t check for fuel or spark. I had this happen once before and it turned out to be a bad connection on one of the 4 little cubes (can’t remember what they are called) that plug in above the coil. I pulled each one and plugged them back in and it still would not start. I had to drive the dang F-150 with its 11mpg. It looks like I now have something to do tonight.

Any ideas?

 

Im putting my money on CPS, sounds like the classic CPS issue.

 

X2 you can usually get buy with plugging and unplugging it back it, Usually the connector is the thing that goes first.

http://yuccaman.com/jeep/cps.html

 

Yeah these two guys posting before me are probably right. The plugging and unplugging works about 80% of the time. The CPS should be changed out at your earliest convience though so this doesn't become a permanent no start situation.

 

The CPS will be the first thing I check tonight. I replaced it the last time this happened but it was not the problem.

 

Could be the main wiring harness connector side of the CPS. Best way to check is unplug it and plug it back in a few times and test

 

Ok, are you ready for this? You probably all heard the scream around 6pm MDT. I got home with a plan of attack for this beast and thought I would just crank it over to see what happens. Well guess what? This (Dirty word of your choice) fired right up. I know this POS is going to leave me on the hill somewhere.



Currently, I always run with a spare left and right axle, u-joints and wheel bearing for the front, a spare drive shaft, a spare CPS and TPS, fuses, hoses, belts, gasket material and cement, fluids, fix-a-flat and plug kit, compressor and all the tools needed to strip it down into little pieces and put it back together.

Anybody have any idea what else I should carry to be able to get my a$$ home?

 

Are you sure that the CPS isn't grounding itself against something? I had one that did the same thing. Turned out the CPS wiring had been scraping against the exhaust manifold and had melted through. It would ground itself out against the manifold and not let it start. and then you would move the wiring and Bingo... it started and ran fine.

 

I had that happen on another XJ I had. On this one, I've got the wiring attached to the firewall to be sure it stays away from the exhaust. Between this morning when it would not start and tonight when it did start, it just sat in the driveway, nothing was touched. The only thing that changed was the temperature.

 

Same thing happened to me two weeks ago. I was getting ready to go out of town on business and the Jeep would crank but wouldn't start. Woke the wife up and had her run me into work. Got home a week later and it fired right up. I started running diagnostics and couldn't find anything out of the norms with my digital multi meter. I decided to check the main wiring harness connection - it was tight. Went to check voltage on the CPS again and it was below specs. Thought that was odd, so I shook the main harness and checked it again - guess what - back to normal. Unplugged the harness and started checking each individual pin until I found one with no resistance. Ended up being a partially broken wire in the harness. I cut out the bad section of wire and soldered the wire back together. Checked the rest of the harness, it was all within specs. Haven't had a problem since. Guess it's all part of owning a 20 year old Jeep. An hour or two of diagnostics and a little soldering solved my issue. Just something for you to think about. If you can't find anything out of the ordinary now and it happens again, try shaking the harness. If it starts after that, then you know you've got some wiring issues to chase down. HTH

 

Thanks Montana, Old wiring is kind of what I suspect the problem to be. I have found in the past that once you start playing with it, you could cause more problems than the one you are trying to solve. After a run this weekend, I’ll have a few weeks before hunting to inspect it.

 

How about the porcelin ballast resistor, seen that cause inexplicable intermitent no-start issues

 

Do you have a test for it?

 

You can jumper it as it is just a reduced voltage to quieten the noise of the fuel pump. Many people have just eliminated them.

 

Thanks for the info.