1997 Chevy Blazer, 4.3L, Auto, "W" VIN code.

What is the most likely cause for the oil pressure gauge to be pegged max at all times (ignition on, off, cranking, running)? Should I be looking for a bad sending unit? Open/short wire in the harness somewhere? Bad gauge cluster? Is there a way to test the sending unit other than replacing it with another one? And finally, where exactly is the sending unit located on this?

I have only had this rig about a month, and the oil pressure has never read right. I bought it from a small town, rural airport and there were a couple radios and a light bar on it, that the airport removed prior to the sale. I do not think that they took a whole lot of care when removing the excess equipment.

Thanks for the help in advance.

 

The oil sending unit is under the distributor. It's just on the driver's side of the block just below the LIM. It is on the very rear part of the block and seats on the same mating surface the LIM attaches to. An adapter is screwed into the block and the unit itself is then screwed into adapter that at a 90 degree angle. It's very close to the firewall (and a real pain to get to) so there could be a possibility that the sheathing on the wire has worn thru (though I don't know if a symptom of that would be the gauge pegging out).

 

Best to check oil pressure with a manual gauge like rockp2 suggested, and post the results. If pressure indicates too high, (~80psi +) the oil pressure bypass valve in the engine block is restricted, (under $20 in parts to fix). If it indicates normal, there's a problem in the gauge circuit.

If there's a short to ground, either in the wiring or in the sending unit, the gauge will peg at minimum. If there is an open circuit, either in the wiring or in the sending unit, the gauge will peg at maximum. You can try unpluging the connector and ground the tan with white stripe wire, then turn the ignition to the run position. If the dash gauge goes to minimum, you probably need a new sending unit, (they're not known for their reliability, accuracy or longevity). Kinda like an idiot light, except this is an idiot gauge

 

Thank you for the info. Now that I know what a short and open cause, I can give that a try in the next couple days and see if it is in the sensor or the wiring.

 

Is it pegged at 80 psi, or did it go way past that? if it went past it your sensor most likely isn't sending a signal to the gauge. I just replaced mine and when I unplugged it my gauge went way past 80.

 

Just For Your Information; in order to even get to the oil pressure sensor connector the distributor will likely need to be removed. Might also think about taking the hood off, which is easier than taking the distributor out, just to have more room and light to see into this area.

It is a very tight area!

 

I couldn't get mine out without removing the disributor. If you don't know how the distributor works i suggest you Google it. you have to mark how it comes out before you put it back in. there are some good YouTube videos of it.