Crank but no start

[KingCarGuyZ]

Ok, went out to the Jeep today and replaced a idler pulley and tensioner. (2001 4.0 manual jeep btw) Fired her up afterwards and she ran great, even fixed the pulley chatter. Then I noticed I had a check engine light so I turned the Jeep off, got the reader and read a po118 coolant temperature sensor one high, I then cleared the code and went to start the Jeep up again, and she didn’t.

She cranks great and all my gauges seem to be reading fine. Battery voltage is dropping and such, there is a smell of fuel from the exhaust which leads me to believe injectors are working fine. And I did new plugs about a month ago. Anyone have any idea what I managed to break? I’m kinda confused as to what would make her not start so suddenly. any trouble shooting advice or experiences would be much appreciated, THANKS!

 

[Daryl]

Check your coil wire.

Edit: just realized you have an 01 with a coil rail and not the earlier style with a single coil.

 

[KingCarGuyZ]

Just pulled the ignition rail and the boots look fine, currently fighting with the electrical connection so that I can test the coils resistance.

 

[Whitetrash]

I had read somewhere that the coolant temp sensor has caused some Chrysler engines of our era to randomly not start, might want to test it, or just replace it since they are fairly cheap!

 

[KingCarGuyZ]

I just put the rail
Back on, tested the coils and got 16.3 for 1&6 15.8 for 2-5 and 15.3 for 3&4 put it all back together and cranked the Jeep and she started. Idled fine but the second you tried to give her any throttle slowly she tried to die. If you jammed it she would kind of try and rev. I killed her and then tried to re-start but it took pinned throttle and was missing and running wayyyyy rich.
im guessing TP sensor or crank sensor, what do y’all think?

 

[Whitetrash]

I just put the rail
Back on, tested the coils and got 16.3 for 1&6 15.8 for 2-5 and 15.3 for 3&4 put it all back together and cranked the Jeep and she started. Idled fine but the second you tried to give her any throttle slowly she tried to die. If you jammed it she would kind of try and rev. I killed her and then tried to re-start but it took pinned throttle and was missing and running wayyyyy rich.
im guessing TP sensor or crank sensor, what do y’all think?

You can easily test the TPS to see if its bad with your voltmeter. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. At idle, TPS output voltage should be greater than .26 volts but less than .95 volts. Move the throttle and look for smooth meter response up to the 4.49 at WOT. The other wire will be the ground and should show no voltage.
Maybe the crank sensor, but typically it just wont start at all, or will start and run like crap. I still think you should test the Coolant Temp Sensor, you got a random code for it, why not try to rule that out? A bad one has been known (at least from what ive seen and read) to give some really weird issues.

 

[KingCarGuyZ]

I just ran the tps test and that passed, I have to go run some errands, but I’ll test the coolant temp sensor before I go drop money on a CKP. Before I go googleing, you wouldn’t happen to know the percedure to test the coolant sensor?

 

[Whitetrash]

There is a chart floating around somewhere, its measured in ohms. For example, at 100 degrees its at a certain ohm, and 210 is a certain ohm, etc. They are fairly cheap to replace, i would just try that honestly. Just make sure if you do replace the CKP, you get Mopar. The parts store ones are VERY hit or miss, I went through 2 parts store ones on my 318, both having random idling issues, before I learned simply putting in a Mopar CKP solved all my issues.

 

[KingCarGuyZ]

Just replaced the coolant temp sensor with one from the leprechauns for 30 dollars with tax, Jeep started up a little hard but fine, ran great no hesitation on the throttle and idled fine, let her run for about a min then killed and re-started. Started even better the second time (I’m attributing that to all the cranking) I’m gonna take her all the way up to temp either tonight or tmr before I declare her fixed, but the temp sensor definitely helped, thanks for the wisdom @Whitetrash

 

[Whitetrash]

Just replaced the coolant temp sensor with one from the leprechauns for 30 dollars with tax, Jeep started up a little hard but fine, ran great no hesitation on the throttle and idled fine, let her run for about a min then killed and re-started. Started even better the second time (I’m attributing that to all the cranking) I’m gonna take her all the way up to temp either tonight or tmr before I declare her fixed, but the temp sensor definitely helped, thanks for the wisdom @Whitetrash

No problem man! Glad I could be of assistance! Sometimes it is the small things you overlook, (like getting that random code and not thinking much into it) that can cause things to be difficult. Once you drive it around a bit, report back!

 

[KingCarGuyZ]

I just ran the Jeep through a temp cycle, all the way up to 210. She started cold great and no problems through the drive, after we shut her done she started right back up and ran great with no problems, seems like the new temp sensor worked. Hope this helps someone else with the same problem.

 

[Whitetrash]

I just ran the Jeep through a temp cycle, all the way up to 210. She started cold great and no problems through the drive, after we shut her done she started right back up and ran great with no problems, seems like the new temp sensor worked. Hope this helps someone else with the same problem.

Glad you took that piece of advice man! Keep on Jeepin!