Help!!! No start when hot....not crank sensor

jws84_02 · **Posted:** Mon Sep 11, 2017 1:43 pm

Alright guys. Need some help. I was down to do a timing belt on a guys jeep and also change air conditioner compressor and he had symptoms of what I thought was crank sensor so I changed it out with a new one.

Anywho, fired it right up after timing belt job, took it for a cruise got it up to temp. Came back to his shop, shut it down and the first time I went to re start it it started. After that it wouldn't. During these episodes that he says keeps getting more frequent. It will crank and right away it seems like it will fire for a brief second and then it acts like its out of fuel.

I tried a cam sensor with no help.

And the kicker is there are no codes

Locked KJ · **Posted:** Mon Sep 11, 2017 5:34 pm

Does said jeep have a lift pump? I was just dealing with basically the same symptoms ( trouble restarting when hot ) and it was cured by a lift pump. I would run into a store quick and when I tried to start it, the jeep would seem out of fuel and I would have to hand prime the filter head.

jws84_02 · **Posted:** Mon Sep 11, 2017 6:17 pm

No the jeep doesn't have a lift pump. But the filter was pumped and bled everytime before cranking to be sure that wasn't it. Like stated, it's starts perfect on a cold engine. Something is heating up and causing something weird to not allow it to fire

GordnadoCRD · **Posted:** Mon Sep 11, 2017 7:58 pm

Have you checked cranking voltage?
You say you tried a cam position sensor with no result.
You say it's not the crank position sensor, but how did you reach that conclusion? The symptoms sound very much like that's what it is.
The only other thing that comes to mind is the neutral safety switch, or shifting interlock out of adjustment, but that usually causes it to not crank over.

jws84_02 · **Posted:** Mon Sep 11, 2017 8:23 pm

GordnadoCRD wrote:

Have you checked cranking voltage?
You say you tried a cam position sensor with no result.
You say it's not the crank position sensor, but how did you reach that conclusion? The symptoms sound very much like that's what it is.
The only other thing that comes to mind is the neutral safety switch, or shifting interlock out of adjustment, but that usually causes it to not crank over.

I put a new crank sensor in as I stated the original post. I never did meter voltage. That was one idea I told owner to try after the fact I left his place.

GordnadoCRD · **Posted:** Mon Sep 11, 2017 8:56 pm

Sorry, I missed that you had changed the CKP sensor.
Did you check the Loom-side connector for the CKP sensor and the wires behind it? Am told that problems there are common, as it is on close proximity to the exhaust down pipe, and isn't protected by the CKP sensor heat shield.

jws84_02 · **Posted:** Mon Sep 11, 2017 9:04 pm

GordnadoCRD wrote:

Sorry, I missed that you had changed the CKP sensor.
Did you check the Loom-side connector for the CKP sensor and the wires behind it? Am told that problems there are common, as it is on close proximity to the exhaust down pipe, and isn't protected by the CKP sensor heat shield.

I will relay that advice. Thanks

rankom · **Posted:** Mon Sep 11, 2017 9:33 pm

can you check fuel rail pressure , also unplug Mprop valve at cp3 to send max pressure to rail , but make sure low pressure side does deliver fuel to cp3.

rankom · **Posted:** Mon Sep 11, 2017 9:33 pm

can you check fuel rail pressure , also unplug Mprop valve at cp3 to send max pressure to rail , but make sure low pressure side does deliver fuel to cp3.

blueray · **Joined:** Thu Aug 03, 2017 10:44 am **Posts:** 6

I bought my jeep two months ago, so I'm new to it. My Duramax had the same problem. It wouldn't start hot, but fired right cold. It was my injectors. Could it the injectors?

Help!!! No start when hot....not crank sensor

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