6.2 Water Temp Sending unit

[choots]

I have 1987 6.2. I took the sending unit out of the back of the head which was closer to the top of head, replaced it with manual gauge & sending unit combo. This was on the passenger side head, New Gauge works, also the gauge on the dash works??? Now it will not start in the morning until I pump the throttle. After checking further I plugged the old sending unit into the wires that I had strapped up & the glow plug light works on the dash. Unplug the sending unit & the glow plug light will not work. Have I taken the wrong sending unit out & If so where is the one located that I need to take out? I prefer the manual add on gauge.

[john8662]

Sounds like you've removed the Fast Idle and Timing Advance switch that is located on the passenger's side rear cylinder head near the firewall. This switch (not sender) has two wires on it. One wire is power, the other wire goes through the harness to the injection pump and fast idle solenoid.

So, put this back in.

The sender you're looking for is located on the driver's side of the engine bay, at the front of the cylinder head, just above the powersteering pump, or below the a/c compressor.

It just has 1 wire on it.

My recommendation:

Purchase a blockoff plate for the rear cylinder head that has the 1/2 threaded inlet on it and mount your new gauge sender there. This will be the HOTTEST coolant path on the engine. Then, leave the factory gauge AND cold advance Switch in place and functional. You can use the factory gauge AND your new aftermarket gauge and compare the two, for a reference.

J

[diesel65]

You took out the sender for the temp inhibit circuit to the glow plug controller, the fast idle and timing advance is the sender closer to the exhaust manifold on the passenger side.
The sender for the guages is on the drivers side head behind the power steering pump.

Just put a jumper wire across the connector and tape it up, GM had a service bulletin
for warm engine hard starts, they had you replace the sender so the glow plugs would come on at all times when starting.
I happened to break mine and found a shorting bar inside the brass fitting.