1990 2.9 - fuel, temp, oil pressure gauges not working

zapfed · #1 01-17-2011, 07:57 AM

Fuel, temp, and oil pressure gauges do not work. Other instrument cluster warning lights seem to work (seat belt, high beam,... all ok). All fuses under the dash are good. Is there an additional fusible link or something that the Haynes manual does not show? I just acquired the truck, so I don't know when the gauges stopped working, but I am assuming they are related...? Any ideas please?

SEOHIO · #2 01-18-2011, 04:30 PM

I have the same problem with my 91! No Idea!

zapfed · #3 01-18-2011, 07:31 PM

I can't find any information anywhere. I think I will assume that all 3 sending units are bad. I will start troubleshooting one at a time, I guess...

1KOOL1 · #4 01-19-2011, 09:05 PM

Quote:

Originally Posted by zapfed

Fuel, temp, and oil pressure gauges do not work. Other instrument cluster warning lights seem to work (seat belt, high beam,... all ok). All fuses under the dash are good. Is there an additional fusible link or something that the Haynes manual does not show? I just acquired the truck, so I don't know when the gauges stopped working, but I am assuming they are related...? Any ideas please?

I think there is a dash guage voltage regulator on the back of the instrument panel that cuts the voltage down from 12 volts to 5 volts going to the guages. Probably don't want to shoot 12 volts directly to the guages!!! Check with an auto parts store & see if they have a dash guage voltage regulator for your truck model. I'm not at my shop now or I could look that up for you. Good luck & let us know what you find. Hope this helps.

zapfed · #5 01-20-2011, 04:28 AM

Oh! That makes a lot of sense. If I can identify the voltage regulator, which I think I can, then I should be able check the input and output to determineif it works. Thanks!

zapfed · #6 01-21-2011, 02:30 PM

Update - I located the temperature sending unit, removed the wire and jumped it to ground and the temperature gauge shot up. Gauge is fine, sending unit is bad. Located the oil pressure sending unit, did the same test, got the same result. I did not test the fuel sending unit yet, but I expect to get the same result. All 3 sending units really ARE bad! Whooda thunk it?

SEOHIO · #7 01-22-2011, 10:19 AM

How Did u do it???

zapfed · #8 01-23-2011, 07:57 AM

Steve, I have attached some photos of how to test the temperature sensor. First photo shows the location of the sensor on the engine near the top radiator hose. Second photo is a close-up view. Third photo is what to do:
1. Remove the wire from the sensor.
2. Jump the wire to some convenient chassis/engine ground.
3. Check the gauge with the key in the ON position. If the temperature gauge goes to full hot with the wire jumped to ground, then you know the gauge is good and that the sensor is bad.
The oil pressure sensor looks similar and can be tested the same way. It is located on the driver's side, low on the engine block, right in front of the engine mount. It is a bit difficult to see, but you can get to it from underneath the truck.
$7.99 for the temp sensor and $9.99 for the oil pressure sensor at Advance Auto Parts. It was really quite cheap and easy, it's nice to have those gauges working. I have not done the fuel sensor yet as it is expensive and a little more difficult.
Good luck.