1997 TJ crank no start

Kurt97TJ

New Member
Feb 4, 2019
7
Glendale, CA.
I need help with a crank no start issue on my 1997 TJ 4.0 5speed. I am at a loss, I have done:
-I have good spark tested all plugs (new cap, rotor, and wires)
-I have fuel (rail pressure 45lb, sprayed starter fluid in manifold no start, pump comes on with ignition for few seconds)
-New: MAP, TPS, Crank PS, Cam PS. (5v to all from PCM)
-ASD rely swapped with good horn relay.
-All fuses good.

Has been misfiring and sputtering for a few months and now no start at all.
Thanks
 
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Kurt97TJ

Kurt97TJ

New Member
Feb 4, 2019
7
Glendale, CA.
X2, a bad coil can produce spark... just not enough of it. Avoid aftermarket coils like Screaming Demon etc.
I tested the coil and was within ohm specs, but I also got an O'reilly "masterpro" coil just to test for any difference and got no change, so I reinstalled the stock one. (FYI: I replaced all sensors with mopar ones)
 
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JPAZIDO

New Member
Feb 4, 2019
9
Glendale Arizona
Just for fun, how is your battery? When the TJ battery goes "weak" NOthing is predictable, anything can and will happen. IT basically goes nuts. Check your voltage with the jeep not running. Long shot but it sounds like you need a long shot. :)
 

ac_

zombicon
Supporting Member
Jun 15, 2017
4,093
AZ, United States
As mentioned earlier,
Spark
Fuel
Compression.

If you have spark and fuel, I would do a compression test. After that if it passes, I would go back to the spark. It sounds like your fuel is right on, unless your injectors are not injecting. An easy way to test that is carb cleaner or either in the air cleaner. Spray some in and try and start and see if it wants too. If there is no change, I would go back to checking the spark.

You have something basic wrong. Stop replacing computer parts till you figure out what is wrong?

Is it backfiring like say though the carb(Throttle body?)

For the the most part your computer won't stop your car from running, it can run bad, but it still should have a limp in mode.

Check all of the timing. Put it on Top Dead Center and make sure the crank and distributor line up with the number one plug wire. That will check your timing chain/gears. Although if they are far enough off to not have your jeep try and start it should be backfiring through the intake. That is one of the reasons why I asked.

One last thing to try. Pull all of your spark plugs and keep them in order, and see if they are different colors or the same. sometimes you can spot a troubled cylinder if one or two spark lugs are different than the rest.

Keep us posted.
 
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Kurt97TJ

Kurt97TJ

New Member
Feb 4, 2019
7
Glendale, CA.
Just for fun, how is your battery? When the TJ battery goes "weak" NOthing is predictable, anything can and will happen. IT basically goes nuts. Check your voltage with the jeep not running. Long shot but it sounds like you need a long shot. :)
The battery is good.
 
OP
Kurt97TJ

Kurt97TJ

New Member
Feb 4, 2019
7
Glendale, CA.
As mentioned earlier,
Spark
Fuel
Compression.

If you have spark and fuel, I would do a compression test. After that if it passes, I would go back to the spark. It sounds like your fuel is right on, unless your injectors are not injecting. An easy way to test that is carb cleaner or either in the air cleaner. Spray some in and try and start and see if it wants too. If there is no change, I would go back to checking the spark.

You have something basic wrong. Stop replacing computer parts till you figure out what is wrong?

Is it backfiring like say though the carb(Throttle body?)

For the the most part your computer won't stop your car from running, it can run bad, but it still should have a limp in mode.

Check all of the timing. Put it on Top Dead Center and make sure the crank and distributor line up with the number one plug wire. That will check your timing chain/gears. Although if they are far enough off to not have your jeep try and start it should be backfiring through the intake. That is one of the reasons why I asked.

One last thing to try. Pull all of your spark plugs and keep them in order, and see if they are different colors or the same. sometimes you can spot a troubled cylinder if one or two spark lugs are different than the rest.

Keep us posted.
I have not done a compression test.
I have sprayed starter fluid (see above) and no change.
There is no backfire through the intake and no hiccup of trying to start.

The sensors have been replaced over the past few years and I know from experience that if the crank or cam sensor goes bad it will not start.

All the plugs are good.
 

ac_

zombicon
Supporting Member
Jun 15, 2017
4,093
AZ, United States
by good you mean the same color?

If the crank and cam sensor goes bad what happens to make it not start? Does it cut the spark or the fuel?

I honestly don't know the answer to that question, but seems if you have spark, and fuel and compression it should run regardless, so I am assuming if the crank sensor or cam sensor go bad then it stops one of those two things.

Maybe someone smarter than me can school me on that. I am curious. I haven't learned that by experience yet, and if that is true I hope not to.

From what I know though other than that is if you have bad sensors your car will go into a limp in mode, and let you get home. I always assumed that went with the crank and cam sensors too.

Do you have any codes? I am still leaning on something basic though. I don't think it is fuel related because starting fluid would have at least made it try.

I think you have a compression issue or something weird with the spark. Have you checked inside your cap for moisture. That could do it. although sometimes it will try and catch and at least backfire in the intake. but sometimes if it is wet enough it just won't start.


Now you got me curious damnit!
 
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Kurt97TJ

Kurt97TJ

New Member
Feb 4, 2019
7
Glendale, CA.
by good you mean the same color?

If the crank and cam sensor goes bad what happens to make it not start? Does it cut the spark or the fuel?

I honestly don't know the answer to that question, but seems if you have spark, and fuel and compression it should run regardless, so I am assuming if the crank sensor or cam sensor go bad then it stops one of those two things.

Maybe someone smarter than me can school me on that. I am curious. I haven't learned that by experience yet, and if that is true I hope not to.

From what I know though other than that is if you have bad sensors your car will go into a limp in mode, and let you get home. I always assumed that went with the crank and cam sensors too.

Do you have any codes? I am still leaning on something basic though. I don't think it is fuel related because starting fluid would have at least made it try.

I think you have a compression issue or something weird with the spark. Have you checked inside your cap for moisture. That could do it. although sometimes it will try and catch and at least backfire in the intake. but sometimes if it is wet enough it just won't start.


Now you got me curious damnit!
Yes, all the plugs match color.

The crank sensor on the bellhousing reads magnets in the flywheel telling the computer the position of the crank. This controls the timing of the spark.

The cam sensor reads the position of the cam telling the computer when to fire the injectors.

As these sensors start to go bad they will not accurately relay this information and the engine will start to misfire. Once the sensors stop working the engine will not start, there is no limp mode. I always carry a spare crank and cam sensors.

No codes

The cap is dry and clean
 

ac_

zombicon
Supporting Member
Jun 15, 2017
4,093
AZ, United States
Thanks for the school. That seems like a single point of failure. And a total bummer that you have to carry spare parts just in case.

If your cam sensor and or crank sensors start to go bad don't they throw codes?

Outside of that if you have spark and fuel, and cam and crank sensors, the only thing left is compression.
 
OP
Kurt97TJ

Kurt97TJ

New Member
Feb 4, 2019
7
Glendale, CA.
Thanks for the school. That seems like a single point of failure. And a total bummer that you have to carry spare parts just in case.

If your cam sensor and or crank sensors start to go bad don't they throw codes?

Outside of that if you have spark and fuel, and cam and crank sensors, the only thing left is compression.

Finally found the problem, I started slowly working my way through the loom to see if there were any bad grounds or worn/damaged wires. when I got to the connections to the PCM they had a lot of moister in them and I could shake a little water out of them. I dried them out and the jeep fired right up.

To prevent this problem in the future I have used dielectric grease on these connections and I am making a new custom cover as I believe the water was coming in from the gap between the hood and firewall allowing water to fall directly on the PCM and connections.
 
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ac_

zombicon
Supporting Member
Jun 15, 2017
4,093
AZ, United States
Finally found the problem, I started slowly working my way through the loom to see if there were any bad grounds or worn/damaged wires. when I got to the connections to the PCM they had a lot of moister in them and I could shake a little water out of them. I dried them out and the jeep fired right up.

To prevent this problem in the future I have used dielectric grease on these connections and I am making a new custom cover as I believe the water was coming in from the gap between the hood and firewall allowing water to fall directly on the PCM and connections.

Congrats! Nice detective work!