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Here's a new one, I think!
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=84226		 Page 1 of 1
Author:  Mountainman [ Tue Mar 15, 2016 12:42 am ]
Post subject:  Here's a new one, I think!
So, I fire up a jeep to pull it in the garage, only I have the coolant temp sender disconnected (robbed the part, long story), anyhow, it revs up to about 1800 rpm's all wild like, and then idles for a few seconds and dies. I repeated this a few times before I plugged in a temp sender, and then it ran fine.

I'm thinking if the wire for the sender was damaged, that you'd be dead in the water, and the symptoms would be this weird rev up and run for a few and die. FWIW, hopefully this helps someone someday :5SHOTS:
Author:  flash7210 [ Tue Mar 15, 2016 8:10 am ]
Post subject:  Re: Here's a new one, I think!
I think that with the temp sensor unplugged the ECU thinks temp in like 0 deg Kelvin or something stupid like that :lol:

Also, I think I remember Yeti mentioning that unplugging the temp sensor will help the ECU keep the glow plugs on longer for improved cold starting. But it must be plugged back in to keep it running right.

Like everything else on this engine, if a sensor is unplugged the ECU will loose its mind.
Author:  Mountainman [ Tue Mar 15, 2016 11:08 am ]
Post subject:  Re: Here's a new one, I think!
Yeah, it's kind of strange that the ECU let it start, and then later decided that it's too cold, hot, or has no input, and shuts it down. Even stranger that the rpms jump so high. This is a GDE eco tuned jeep, I forgot to mention that detail, probably wouldn't matter either way.
Author:  Hexus [ Tue Mar 15, 2016 11:38 pm ]
Post subject:  Re: Here's a new one, I think!
Yeah, it won't run right with the stupid sensor on the back of the thermostat unplugged.

Ask me how I know....
Author:  geordi [ Wed Mar 16, 2016 1:49 am ]
Post subject:  Re: Here's a new one, I think!
Very interesting. Keith or Yeti would have to weigh in on how that sensor is tracked through the ECU programming. Obviously it goes open-loop right after starting and that *really* pisses off the computer if that sensor data isn't there.

2+2 suddenly divides by zero and equals bullfrog in the computer?
Author:  papaindigo [ Wed Mar 16, 2016 7:04 am ]
Post subject:  Re: Here's a new one, I think!
We know for past forum comments (including Keith IIRC) that the coolant temp sensors feeds/produces real temps in degrees F/C to the ECU which in turn determines the temp gauge unmarked, in degrees, needle position. We also know coolant temp at least relates to AC and viscous heater operation and probably to fuel injection amount/timing. Hence it seems logical that a report of no temp to the ECU would cause the system to go nuts. That said I would have assumed a no start with code not a start/high rev/die.
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