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Does the guage tach out when the ignition switch is turned on with the engine turned off?
If so, unplug the green wire (ignition switch still on) and see if the guage drops. If so, replace the sender. If not, continue.
Follow green wire to bulk head, actually inspect all of the wire looking for cuts, corrosion, butn marks, or obviously, seperation. If so, repair and check...if not....
Find where the green wire goes on inside of firewall. I'm sure it runs to a fuse, and then into the main under dash harness. Inspect and check the wire all the way to the insterment panel plug. If damaged, repair and check. If not...
Remove insterment panel. Obtain a digital multimeter. A cheap one can be had at sears for about 50 bucks. Decent ones at just over 100 dollars. Look at the plug, and determine what pin (for lack of a better description) the temp wire is, and see which circuit it follows on the circuit board. Follow that circuit looking for obviouse burns, tears or any other visable breaks. If damage found, repair and check, if not...
Get the multimeter, place the selector on ohms, (looks like a hose shoe, or an upside down U) or put it in continuity...this selection is pretty much the same as ohms for this kind of test, but has an audible indicator letting you know there is continuity Then place one probe (doesn't matter which one) where the plug goes on the determined circuit, (marking it with a marker is a good idea, they all look the same after a few min) and then poke the other lead into that circuit at the guage. If no continuity, then keep movinh the second lead back up the circuit untioll you have \ontinuity, once you obtain continuity, go back towards the guage in smaller incriments untill you don't have continuity anymore, and that will indicate an open circuit. If problems are found, repair/replace circuit board and test. If not...
replace the guage.
Do not worry about shorting anything out. Example, the green wire. When you unplig it, if it hits the frame, it will not spark. The guage reads amount of ground...or resistance to ground. 0 Ohms is tached out on the guage...way hot. 90 ohms (I think is the number on these) reads bottom cold.
If I left anything out, please feel free to add to this.
If it tachs out as you describe, then the circuit is grounded somewhere.
Guff, the sending unit should be the same regardless of engine if i am not mistaken. If the connector does not look like a nail head, then you have the wrong sender.
Thread tape can cause problems, and you really don't nead it anyways. The sending unit should be pipe thread. Pipe thread has a small tip, and gradually gets bigger as you thread it in. Hold one up infront of you in the light...you'll see it.
However, the thread tape would not cause the problem indicated, it would cause a guage to never move...stay bottomed out from lack of a good ground.
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