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 Post subject: Another case of hot no-start
PostPosted: Mon May 14, 2012 10:06 pm 
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LOST Addict

Joined: Thu Oct 20, 2005 5:42 am
Posts: 2121
Location: Fort Collins, CO
Here is the sequence of events:
My wife tells me one day she came back to start her jeep which was already hot. It took a long time cranking but eventually fired up fine, with no codes.
1wk later, same thing.
1wk later, Jeep wouldn't start at all hot. Let it cool and all was fine.
1wk later, it almost died on me while in a drive thru. It was like all the injectors quit firing for a quarter second, but afterwards kept running smooth and with no codes.
1wk later, while I was out of town, of course, it died on her at a stoplight. After cranking for a while it started up and drove fine. After getting to her destination, it wouldn't start at all and she had to get a ride home.

After reading jeepdan's saga, the first thing I suspected was the crankshaft position sensor. So I took it out and did the same heat gun test on it. It started out at 1100 ohms and steady, but after only about 30 seconds the resistance skyrocketed up to 40kohm and bounced around between there. It's silly that this doesn't throw a MIL or something. It seems like this is going to be the year of the bad crank sensor here at LOST CRDs. I found a couple other threads relating to that.

New sensor is on the way, should be here Friday. Big thanks to jeepdan for doing the legwork on that one.

To remove the crank sensor, the best way is from under the passenger side. There is a small heatshield on the block, below the turbo, which protects the sensor from heat off the downpipe. Remove the two 10mm bolts holding it on and you can drop it out and see the sensor. An 8mm bolt holds the pigtail bracket to the engine, I had to remove that just to squeeze the plug locking tab. Then a 5mm allen will remove the sensor from the block, it sticks about 2 inches into the block and will come out oily.

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05CRD: GDE Hot ECU & TCM tunes, Provent, Cat filter, Facet lift pump, TransGo kit, Florida TC, Samcos, stainless brake lines, HDS thermostat, Renegade light bar,
RL super sliders, Bilstein adjustables, Al's Gen 4.5 Arms, 235/85-16 Duratracs, DTT rear, Elocker front, EVIC+TPMS, Turbo timer, McNally pillar gauges, Weeks Stage II kit.


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 Post subject: Re: Another case of hot no-start
PostPosted: Tue May 15, 2012 6:08 am 
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Joined: Sun Jun 07, 2009 5:10 pm
Posts: 1111
Would you be willing to ship me the failed crank sensor for analysis? I would like to verify the functionality vs. the diagnostic limits in the calibration. We might be able to adjust our tune to be able to detect this issue in the future. Thanks

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 Post subject: Re: Another case of hot no-start
PostPosted: Tue May 15, 2012 6:04 pm 
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Joined: Thu Oct 20, 2005 5:42 am
Posts: 2121
Location: Fort Collins, CO
Sure, I'll send it to you. Once I get the new sensor in and running I'll ship it out.

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05CRD: GDE Hot ECU & TCM tunes, Provent, Cat filter, Facet lift pump, TransGo kit, Florida TC, Samcos, stainless brake lines, HDS thermostat, Renegade light bar,
RL super sliders, Bilstein adjustables, Al's Gen 4.5 Arms, 235/85-16 Duratracs, DTT rear, Elocker front, EVIC+TPMS, Turbo timer, McNally pillar gauges, Weeks Stage II kit.


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 Post subject: Re: Another case of hot no-start
PostPosted: Sat May 26, 2012 11:21 am 
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Joined: Sat Jan 31, 2009 1:06 am
Posts: 17
Location: Atlanta GA
Hey guys I'm having the same problem with my car and papaindigo directed me to this thread and it helped me out tremendously!!! I can also send u the old sensor after I replace it today with the new one. Im hoping this will be the only problem with the car so far, a mechanic from the dealer told me that it could be the fuel pump but i hope it's not. Ill find out this afternoon if the sensor is the only problem. If u inbox me ur address I can send u the sensor.

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 Post subject: Re: Another case of hot no-start
PostPosted: Sat May 26, 2012 9:18 pm 
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Joined: Sat May 05, 2012 9:52 pm
Posts: 6
I pulled my crankshaft sensor and tried the heat-gun diagnostic I've seen described. The resistance started out just under 1000ohms, but then it didn't jump to anything super high after being heated. It climbed very steadily to about 1400 ohms (2mins) before I gave up, but there was no "spike" I've seen you talk about. Could this still be the problem?


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 Post subject: Re: Another case of hot no-start
PostPosted: Fri Aug 24, 2012 6:16 pm 
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Joined: Thu Oct 20, 2005 5:42 am
Posts: 2121
Location: Fort Collins, CO
hudunnit wrote:
I pulled my crankshaft sensor and tried the heat-gun diagnostic I've seen described. The resistance started out just under 1000ohms, but then it didn't jump to anything super high after being heated. It climbed very steadily to about 1400 ohms (2mins) before I gave up, but there was no "spike" I've seen you talk about. Could this still be the problem?


Sorry I never saw this question, but no, your sensor sounds good. I would expect it to increase a little and be steady when hot. Did you ever find your problem?

_________________
05CRD: GDE Hot ECU & TCM tunes, Provent, Cat filter, Facet lift pump, TransGo kit, Florida TC, Samcos, stainless brake lines, HDS thermostat, Renegade light bar,
RL super sliders, Bilstein adjustables, Al's Gen 4.5 Arms, 235/85-16 Duratracs, DTT rear, Elocker front, EVIC+TPMS, Turbo timer, McNally pillar gauges, Weeks Stage II kit.


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