I recently pulled my motor out to rebuild it.
I'm using a different GSR head/sensors.... so I can't confirm if those sensors were in working order.
Tonight I was going to break the engine in on the dyno.



First thing I do is prime the engine (crank a few times to get oil pressure/disconnected injectors)
There were 2 issues:

1) With key on IgnII, I notice my TEMP needle would peg all the way up.
The engine start fine.


2) With engine running, TEMP needle is still pegged HOT.
CEL comes on. When I try to pull the code, no CEL shows up.


What I've done so far:

1) check all 3 ECT sensors for loose pins or cracked wiring.... all okay

2) unplug 1 pin ECT "gauge sender" sensor while key on ignII, and needle drops to COLD, and if I connected it, temp needle pegs to HOT.

3) fuses looks good

4) all 3 grounds are fine, engine starts.


Any other ideas?
I may try swapping the ECT gauge sender unit tomorrow

 

My h20 temp sender used to do that, swapped it and all was good. Loose connection (at plug) made it sky rocket.

 

Yep, sounds like a bad sender unit.

 

yup, was bad sensor ect sensor. Put new one in & temp needle works fine.

CEL still shows up, but can't seem to pull the code.

I know that with a bad alternator, it can cause CEL stay on but but alt was just fine when i pulled out motor 4 months ago.

Any other ideas ?