1998 tj wont start.

[kcub]

I have a 1998 tj with 4.0l. Went to start and it would spin over but not crank. Thought it was the fuel pump and droped the tank, pulled pump. Checked the pump with a battery and it started fine. Checked the voltage at the plug and only got .6 volts when ignition turned on.
Changed the fuel pump relay but no change. I even used a jumper at relay and the pump would come on. What could cause the fuel pump not to recive voltage when trying to crank the engine. I'm at a loose as to what to check. Any help would be appreciated.

 

[SteelHeadz]

Check the ckp sensor.

 

[Evil5oh]

Check the ckp sensor.

x2.

I had the same issue on two of my Cherokees. If the crank sensor has failed, the fuel pump will not run. This is a fairly common problem on 4.0's -- I keep 2 spares -- one in the garage, and one in the TJ's toolbox.

 

[kcub]

I checked the cps and it looked like it had rubbed so i put in a new one. Same thing wrong. Fuel pump does not come on when key is turned.
It also doesn't seem to have a spark at the distributor. Pulled the coil wire while the engine was spun over and no arc.
Neither the Fuel gage nor the battery gage seem to work when key is turned on.
Maybe these clues will give someone another guess.
Thanks for the help.

 

[Evil5oh]

This may be a dumb question, but did you look at the cam position sensor, or the crank position sensor? The crank sensor is on the back of the motor above the bellhousing.


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[kcub]

I changed the crank sensor in the transmission bellhousing. This has to be something simple (I hope) It was running fine when parked, now its dead. Could this be a problem with the pcm? What tells the fuel pump to prime and sends spark signal to the coil?

 

[jbjeeper]

i didnt have the same symptoms but the other day i tried to start my 97 tj and it wouldnt even turn over, thanks to a bunch of guys on here telling me to check all my ground connections. i took all my grounds off and cleaned them with sand paper and replaced the end at the sarter and put a new chassis ground on. after i was done she fired up right away and runs better then ever.

 

[kcub]

I checked the grounds, but i'll do it again. Thanks for the suggestion.

 

[Gr8tdragon]

Did You figure out your problem? My 97 has the same issues except I have found a fuse blown for the system, which I have replaced already once.

 

[Jester32]

Check ur asd relay and fuse.

 

[Gr8tdragon]

I have replaced the fuse 2 times. I looked at the asd relay (opened it and checked to see if it grounded or was burnt at points but looked good.) What is down stream other then PCM and coil? Chiltons wiring diagrams are pretty sucky... only things I see on them is the asd, pcm and that the pcm triggers the coil but the coil is also on fuse 21 which my fuse box does not have a 21 in it???? If you know of anything else that could cause the fuse to blow please let me know. I am going to try forwards testing by keeping the relay out disconnecting the PCM and coil. Then I am going to put the fuse in, turn the ignition on, see if fuse blows if no blow then put the asd in as is next in line then move on to pcm feed then output from pcm then coil... till fuse blows. This is the only way to test I can think of with out using the multimeter...it is -35 degrees celcius here this morning so have to wait till this afternoon, hopefully makes it to -15 like they say. I was hoping to hear of a part to target on this forum line as he had same type of problem...could maybe pin point faster. Electrical problems are so fun.

 

[Gr8tdragon]

Well have found that the problem is after the PCM on the third connector from the passenger side of the vehicle or the connector next to the engine on the PCM. Is there any drawings around that are better then chiltons for electrical stuff? Sure don't want tohave to disconnect everything under the hood and attach back one at a time to find the problem if it is under the hood could be under dash as that connector is on the wiring loom that heads behind the engine.

 

[kcub]

The fix for the problem was to replace the computer. I got a scanner and tryed to check for any codes, but the scanner said that it could not communicate with the pcm. The same scanner had been used before without problems. Local dealer wanted 400.00 for pcm + 100.00 to program it. Found one online for 150.00 programmed. When it came in, plugged up - startted up first try. Also, when i plugged it in and turned on the key the fuel and amp gauge worked. ( this was one of the symptoms that had me checking the PCM ) My daughter had jumped a friend off at school is the only thing I can think of that may have damaged the PCM. Not sure of the cause but that is what it took to fix it.

 

[Gr8tdragon]

Well I found my problem, It actually warmed up enough the last couple days to be able to work on the Jeep. After finding that the problem was either on the A or C connectors at PCM, I took off all sensors associated with those connectors. The last item I removed was the Oxygen sensor at the manifold...guess what I found... a melted wire bundle... 2 buck of wire and splices and wala the jeep is a running again. Of course I lengthened the wires so that they are not close to the manifold. Don't know why Chrysler would make them so short.

 

[Roundeye]

The fix for the problem was to replace the computer. I got a scanner and tryed to check for any codes, but the scanner said that it could not communicate with the pcm. The same scanner had been used before without problems. Local dealer wanted 400.00 for pcm + 100.00 to program it. Found one online for 150.00 programmed. When it came in, plugged up - startted up first try. Also, when i plugged it in and turned on the key the fuel and amp gauge worked. ( this was one of the symptoms that had me checking the PCM ) My daughter had jumped a friend off at school is the only thing I can think of that may have damaged the PCM. Not sure of the cause but that is what it took to fix it.

Jump starting someone will fry your PCM, or parts of it if it takes alot of current (like if the person getting jumped has a completely dead battery and keeps trying to start) Incorrect jumping procedures can harm your ride too (like hooking positive/positive, negative/negative instead of hooking negative of jumper to bare metal engine structure on dead battery car)

I jumped off a car with a Pontiac Bonneville a few years ago. The guy was stranded and I had jumpers. Hooked everthing up by the book and helped him on his way. Got a check engine light on the way home. When it was all over with, my little act of kindness costed me a computer.

I don't do jump starts any more. Back in the day of points/carb there was nothing to risk, but now it can cost you electronics.