WATER COOLANT TEMP. SENSOR
 

Have any of you guys had any dealings with the coolant temp. sensor on these trucks? I have a 90 model that starts and runs good on a warm day but when the temp gets fairly low, it is hard to start. I have been having to plug the sensor up to get it started in the mornings but later on after the truck warms up, the sensor needs to be unplugged because I think it makes it run rich. I have not replaced the sensor yet because its like $58 and I would like to be sure.
thanks

RE: WATER COOLANT TEMP. SENSOR
 

:-/

Which one are you talking about, there are 3. The one that controls the temp gauge is right next to the thermostat with a single wire comming out of it. There is another one in the bottom of the radiator which turns on the PTC heater under the carb when the temperature is below 60 deg F this one mainly just helps with warm up on cold mornings, neither of these should cause a running issue.

The third one is the most important one, it mounts in the intake manifold coolant passage facing the front of the truck and is the one that actually helps control engine operation. If this one fails or is unplugged it should put the computer into limp mode causing it to run rich. You should be able to go to an auto store and get this one for about $15-25.

About the cold starting problem, I would check to make sure your choke is engauging when you start the truck. The choke richens the fuel mixture to help the truck start and warm up, if this is not opening it would make sence that unplugging your coolant temp sensor helps it start since the computer would put the carb into a default rich condition by disableing the fuel mixture solenoid.