need electrical help

[Coupe]

Hi, i am new to this website and this is new to me as i am not as computer literate as some. a little about myself. Born and raised in Southern California and now that my kids have grown up and moved out I have been spending the last few years building  a 1937 Chevy Coupe and going to car shows all over. i have been helping my Brother put together his 48  Chevy Sedan Deliery up until three months ago when he passed away. i am trying to help  complete the car with a couple of friends as a kind of memorial and now that i don't have him to bounce problems and questions off of i am in need of a little help.
It has a Ramjet 350, 700R trans and we are just getting the engine running but it has a really hard cold start problem. if i can keep it running long enough to warm up it seems to run and start fine.  it has a code 15 (engine temp high) when it is cold. i have traced the wires  of the ECT back to the ECM with no apparent nicks or pinches but when a take a continuity test from either of the two pins in the weather pack plug back to the J plug i get continuity on both pins. could the wires in the weather pack plug at the sensor be touching inside? i really want to get this problem behind me and get on to body mods and such. I don't have everyday access to the car as it is about 70 miles away and need to get it running to move it around..
ANY electrical help will be appreciated as I have pestered Arizona Speed & Marine enough

[enjenjo]

The sensor will have continuity all the time. But you have to measure the resistance. The computer reads the output voltage of the sensor, and compares that to the input voltage to determine engine temperature. You have to check it with an Ohm meter that is designed to read very low resistance.

My best guess is a faulty sensor, they are easily damaged by overtightening them.

[Coupe]

The sensor will have continuity all the time. But you have to measure the resistance. The computer reads the output voltage of the sensor, and compares that to the input voltage to determine engine temperature. You have to check it with an Ohm meter that is designed to read very low resistance.

My best guess is a faulty sensor, they are easily damaged by overtightening them.

I checked out the Sensor and it was within specs. i even put in another sensor to confirm it was not the problem. the continuity i am speaking about is in the plug when it is disconnected from the sensor and the ECM.

[wayne petty]

here is a link to a simular wiring diagram..

http://econtent.autozone.com:24991/znetrgs/repair_guide_content/en_us/images//0900c152/80/09/91/92//large/0900c15280099192.gif

when you unplug the coolant temp sensor...  you should with a digital volt meter see almost 5 volts on the yellow wire...

when you plug it in with the engine warm you should see 1.5 to 2.0 volts on it ...

the ground wire ... black should be the ground circuit... and may connect as shown to other items up on the motor...

when you disconnect the wire from the sensor.. the yellow wire should not show continuity with the black wire... if that is what you were saying...when you back probe the ecm connector with the ecm unplugged...   try not to front probe it... it tends to spread and loosen the connector...


resistance on the sensor... should be
185 ohms at 210F   boiling water...
450 ohms at 160F
1,800 ohms at 100F
3,400 ohms at 70F
7,500 ohms at 40F   in water with ice...

hope this helps....

wayne

[enjenjo]

With the proper tool, a Weatherpac connector comes apart pretty easily, should be easy to check.

[Coupe]

With the proper tool, a Weatherpac connector comes apart pretty easily, should be easy to check.

Thanks, i will check the grounds that may be connected and try to pull the weather pack apart and let you know what i found next week.

[enjenjo]

One more tthing, grounds are important. The engine wiring, and the computer should have a common ground.