YACNS issue (Yet another crank/no start issue)

[DavidG91]

I'm reluctant to post a new thread since several others report similar issues.

I am the original owner of a 2005 Liberty KJ 3.7L.
For several years, it has sporadically failed to start when warm after being off for 5-30 minutes, but not when immediately restarting it.
Sometimes, it's months between occurrences and sometimes it's several times a day. Last week it was several times, almost every time the engine was warm. The engine cranks but the idle is low and goes up and down for a second or two, then it dies, and does that again and again. If I feather the gas pedal when starting, I can sometimes get it to start. If I wait an hour or more it will start.

I replaced the Idle Air Control Valve but that didn't fix it. I checked the fuel pressure and it was in spec starting running and after turned off (but the issue did not occur during the test). Once when the issue was happening, I took off the fuel line pressure test cap, and there was pressure there. This issue persisted even after getting a new Jasper engine. I just replaced the camshaft and crankshaft position sensors.
I guess I'll see whether the issue recurs.

 

[KJowner]

Usually the crank angle sensor, they don't like heat when they get old.

 

[DadOSix]

Fuel pump.

Next time it does this, cycle the key on and off a few times before trying to restart. This process will build fuel pressure.

You could also check the fuel pressure with a gage.

 

[DavidG91]

Fuel pump.

Next time it does this, cycle the key on and off a few times before trying to restart. This process will build fuel pressure.

You could also check the fuel pressure with a gage.

I had tried cycling the key to increase fuel pressure but that didn't let it start.
Just waiting 1+ hours or (sometimes) feathering the gas pedal would make it start.

I'll pay attention to whether I see the issue again with the new sensors.

 

[blackhawk]

If I were You I would check the fuel pressure in ralentí and in the road! Sometimes you got a good reading in ralentí but not in the road in different scenarios

 

[DavidG91]

There are no codes displayed with the key cycling nor saved for a later scanner, but are there any real-time scanners that I could keep in the vehicle and connect when/if it happens again that might show any useful real time data?