Oil Pressure sensor - 1989 GMC C1500

My oil pressure gauge is constantly max'd out no matter what. I have tried unplugging the connector to the sensor that sits right next to the distributor that is screwed into the block, but got the same response from my gauge (max'd out).

A. Is that the right sensor for my dashboard gauge?
B. Why would my oil pressure read over 60psi (max'd out) rather it is plugged in or not?

V8..350...5.7L

My oil pressure gauge is constantly max'd out no matter what. I have tried unplugging the connector to the sensor that sits right next to the distributor that is screwed into the block, but got the same response from my gauge (max'd out).

A. Is that the right sensor for my dashboard gauge?
B. Why would my oil pressure read over 60psi (max'd out) rather it is plugged in or not?

V8..350...5.7L

That sender has low resistance for low pressure and high resistance for high pressure (90 ohms is high according to my 90 factory service manual).

When you disconnect the sender, this cauces very high resistance and the gauge shows high.

You should connect the sender lead to ground (using a fused jumper, of course). Then if the gauge reads 0, the sender is bad; otherwise, it is a bad wire, connection or gauge).

//2000CAYukon

the sender connector has two wires....which is the one I need to ground?

Also, please take a look at my other post entitled "oil sludge build up"......thanx a bunch.

the sender connector has two wires....which is the one I need to ground?

It does not matter. Use a jumper to connect the 2 wires together and the gauge should read zero.

//2000CAYukon

Also, please take a look at my other post entitled "oil sludge build up"......thanx a bunch.

Sure, I can take a look at it.

//2000CAYukon

I did as you stated and connected the two wires together via a jumper wire. With the key off and nothing on, when the two wires are jumpered, the fuel pump immediately starts running. I left the jumper wire there and started the truck anyways and the gauge still reads max'd out.

Is the fuel pump suppose to run when the two wires are jumpered? Again, it is the sensor the sits right next to the distributor, screws into the block on the drivers side.

I did as you stated and connected the two wires together via a jumper wire. With the key off and nothing on, when the two wires are jumpered, the fuel pump immediately starts running. I left the jumper wire there and started the truck anyways and the gauge still reads max'd out.

Is the fuel pump suppose to run when the two wires are jumpered? Again, it is the sensor the sits right next to the distributor, screws into the block on the drivers side.

There are 2 oil pressure sensors. The 2 wire one is for the fuel pump relay (cuts off fuel if no oil pressure). There is another one with only 1 wire and that is for the gauge.

I thought that both sensors were located in the same general area but not 100% sure.

The one wire sensor looks like this: http://198.208.187.182/internet/ViewPartImage.jsp?acdelcoPartNumber=10069218

//2000CAYukon

Ok, found it....the switch/sensor for the oil gauge on the dash is located between the firewall and driver side manifold, midway down the motor. I did the grounding test and the gauge went to 0. I will now purchase a new oil pressure switch, which I found to be really cheap.

Unfortanately, I am having the same exact problem with my fuel gauge.....always reading FULL. Is there an easy similar way to test it?

thanx again guys.......MUCH appriciated.

Ok, found it....the switch/sensor for the oil gauge on the dash is located between the firewall and driver side manifold, midway down the motor. I did the grounding test and the gauge went to 0. I will now purchase a new oil pressure switch, which I found to be really cheap.


Glad to hear it is not expensive.


Unfortanately, I am having the same exact problem with my fuel gauge.....always reading FULL. Is there an easy similar way to test it?

thanx again guys.......MUCH appriciated.

Yes but the sender is in the tank. You will have to disconnected the electrical harness on the top of the tank and ground the right wire.

I can look it up later when I get a chance to get in the garage after the kids go to bed.

//2000CAYukon

That would be great, thanx. Let me know if I can get to the harness without dropping the tank. If I do end up having to drop the tank, how hard is that?

Thanx again....2000CAYukon

That would be great, thanx. Let me know if I can get to the harness without dropping the tank. If I do end up having to drop the tank, how hard is that?

Thanx again....2000CAYukon

I have not dropped the tank on my K1500 (knock on wood); however, there are 2 ways to do it. 1 is to drop the tank and the other is to unbolt the bed and move it out of the way.

The bed is held on with only 8 bolts and can be easier than wrestling with the tank.

I found this on the net http://www.faqfarm.com/Q/How_to_change_a_fuel_pump_in_a_1997_chevy_1500_pic k_up_truck

I am not sure if you can reach the wires on top of the tank or not without dropping the tank or moving the bed.

By the way, the fuel pump sender going bad is pretty common but you should make sure before replacing it.

I will find out what color the wire is later tonight.

//2000CAYukon

According to my 90 factory manual, there are 2 wires for the fuel sender going to the top of the tank. The Black/White wire is the ground for the sender. The Purple/White goes to the gauge. If you jumper those 2 wires the gauge should read empty.

The Gray wire is the power for the pump.

//2000CAYukon