Won’t Crank When Hot

[Beebz]

Hello,

I have an 02 liberty that runs great however if you are running errands and turn it off once up to running temp it won’t crank. If you leave it sit for anywhere from 20-40min it fires right up.
So far I have replaced:

Starter
Starter solenoid
Temp sensors
Battery

Nothing seems to make a difference. It’s not every time you drive it but it does seem to be getting more and more frequently. I can’t trust it and I am starting to run out of ideas. Any help would be appreciated.

Thank you,

 

[Ksat]

When it's acting up, have someone turn the key while and look for +12V voltage down at the starter solenoid. If you don't get anything, you need to backtrack. If you have power there, grab a negative jumper cable and throw one end on the battery negative and the other on the starter case. Turn the key and see if it starts then. If so, you have a bad ground somewhere.

 

[Billwill]

I agree with Ksat but try the following as well when the failure occurs.

Swap over the Starter Motor Relay with an identical one inside the Fuse/Relay Box under the hood.

Re-plug fuses #8 and #28 inside the Fuse/Relay Box in case they are making poor contact.

If that does not help then make sure the Jeep is in Neutral and Park, remove the Starter Relay and with Ignition ON, jumper Female contacts 30 and 87 inside the exposed Relay Slot briefly with a small jumper wire.....engine should turn over.

If it does now turn over then you may have a bad Park or Neutral sensor or a bad Ignition Switch/Actuator Pin Assembly...not uncommon but usually not heat related!

 

[DaveVella1]

Hey mate,

I have a '06 that was having this exact issue. After replacing all things fuel related and considering putting heat sinks in I replaced my fuel pump assembly (that I was told to have been replaced when purchased) and fixed the issue.

I ran all tests, fuel pressure on the rail, battery, solenoid, etc and all indicated no issues. The fuel pump was my last hail Mary and worked.

Hope you find the issue!