My Truck Can Run All Day And The Temp Gauge Barely Gets Off Of Cold So It Sends A Signal To The Comp. That Its Cold So It Is Running Rich. What Can I Do To Fix This? 89 F-150 302

 

Two possibilitys. First is that it is actually coming up to temp, but the sending unit, or units, are bad. If this is the case, you will have good output from the heater for the cabin.
Second possibility and most likely, is the thermostat is stuck open. In this case, the heater output will be barely warm.
If the thermostate is stuck, replace it with a qood quality new one, and use the factory temperature setting. My truck didn't perform right until I checked the thermostat. Factory setting for me is 195, but previous owner had installed a 180. In anything but really hot weather, it wasn't coming all the way up to temp.
Good luck Frank

 

Well know that there are actually two coolant sensors, one for the gauge on your dash and another for the engine's computer.

Just because the dash gauge says cold doesn't mean the engine is and that the computer is getting a cold reading. If you get a check engine light with a code refering to the ECT sensor then you probably have something.

I'd look into the basics first, like feel the top radator hose as the engine warms up and see if you can feel the t-stat open and get the hose hot.

I've put a thermometer in the radiator neck and checked to see if it was hot enough. You may have a problem with the gauge sending unit/wiring.

If you take the wire off the gauge sending unit and ground it, it should peg out the gauge on the dash. That'll verify that the dash gauge is working.

 

The Heater Works Great. I Know Where The Sensor On The Thermostat Houseing Where Is The Other

 

Let Me Rephrase That One Sensor Is On The Thermostat Houseing Where Would I Find The Other Sensor?

 

Ok if the heater is working great, your thermostat is PROBABLY ok. You need to do some trouble shooting, like Justin outlined.
You said the temp gauge doesn't come up to normal. That is the sensor at the thermostat housing. BUT, you also said it is running rich. That is the other sensor. Not likely they both failed same time eh? I don't know where the other sensor is located on your engine.
Try some simple steps to rule out what is or isn't working right. Take the wire off the sensor for the gauge and with the ignition turned on, ground it. The needle should peg out if the gauge is ok.
With the engine cold, open the radiator cap and start the engine. Should not see much water movement at all. This is to double check that the thermostat is working correctly. Hold onto the upper radiator hose. After a few mintues, you will feel it start to warm up and then pretty quickly you will feel it get hot. Water will visibly be moving in the radiator. If this is ok, thermostat is working correctly.
If the gauge is good and the thermostat is working, and the wire is making good contact, your temp sending unit is bad. Change it with a cold engine, and just slip it out and the new one in real quick. You will loose very little coolant.

The rich mixture is a seperate problem. Could be several causes or a combination of problems to cause a rich mixture. Bad temp sensor, fuel pressure regulator, bad plug or wire, could be a long list. The other temp sensor sends a signal to the computer to use for the fuel mixture. A bad sensor should show up as a code on the computer. Don't think it will light the check engine light, but it will store a code.
To avoid chasing old problems, it is always a good idea to clear the codes before you start. Unhook the battery cable and leave it off for 15 minutes. Reconnect the cable and start it up, and go for a drive. It will probably idle bad and may not run great for a few minutes until the computer gets enough current data. After 15-20 mintues driving, pull the codes. Anything that shows up now is definately a current problem. If you get a code for the ECT sensor, check the connection and or replace the sensor.
Don't need anything fancy to check the codes, a paper clip workes just fine. Google search will give you a step by step list of how to pull codes and what they mean. Remember codes won't automatically clear when you replace a faulty part. You have to clear the codes everytime you work on something, in order to see if the problem is solved.
Good luck Frank

 

What evidence suggests it is running rich? smell?

Have you checked computer codes? If not, check them.

The sensor on the thermostat housing is the ECT (engine coolant temp) sensor. That is the sensor that relays information to the computer.

The sending unit for the gauge is on the intake manifold on the drivers side. It is on the forward half of the manifold. On the drivers side, the intake manifold base has two sensors, one is ACT (air charge temp) and the other is the temp sending unit. The sending unit has a 1 wire hookup and is more towards the front of the manifold whereas the ACT is in the middle.

You should be able to find it with that information.

This symptom could even be caused by air bubbles in the coolant system. With the engine cold, take off the radiator cap and verify that it is topped off...and squeeze the upper radiator hose repeatedly and in varied intensity to see if you can get any airbubbles to float up to the top.

Could very well be just a bad sending unit but you may want to try turning it back and forth with a wrench a couple times. I believe the sending unit uses the intake manifold for ground and this may increase conductivity.

 

The Only Code That I Can Come Up With Is For The Ps