Chevy 454 Oil pressure gauge/sending unit trouble - stuck on 60psi

[moonlitcoyote]

I noticed on my last trip that the oil pressure gauge is stuck on the 60 mark. It never moves. So I pulled the gauge out enough to check the connections on the back and everything looked good. So I put my test light on it and 2 of the 3 posts on the back are hot and the other is (I'm assuming) a ground. So my question is.. What now? Could the problem still be the gauge even tho the 2 posts are hot, or does that mean the problem is in the sending unit (I'm assuming thats what it is called). And if it's the sending unit, where would I find it?


Thanks, MJ

[DonD]

"The oil pressure switch and oil sender for older 454's are mounted on the lower  left front of the block just above the  oil pan."

[moonlitcoyote]

Thank you for the picture, I think I saw that when I was under it today. I'll check again tomorrow, do I have to replace both or just one?

[DonD]

The 2 wire is for the fuel pump.

[HandyDan]

Visit this thread.  It includes diagrams on the subject.
http://www.classicwinnebagos.com/forum/index.php?topic=6292.msg25323#msg25323

[moonlitcoyote]

With all the answers about the sending unit, I am guessing that everyone is telling me thats where the problem is??


MJ

[DonD]

As for my posts, you asked where it was, I responded. Don't know if it's bad.

[moonlitcoyote]

In that picture DonD posted, which is the oil sender and which is the switch? Also the silver one on the left, where do those wires go? I found mine yesterday and the wire is broke off, no idea where the wire is or where it comes from though

[DaveVA78Chieftain]

The single wire one is used for the pressure gauge

A tan wire connects to the sender then goes to the bulkhead connector.  From the bulkhead connector the tan wire goes directly to the pressure gauge.








The 2 wire one is used to shut the fuel pump off if the engine stops (like in a car accident)

[moonlitcoyote]

Thanks Dave, the 2 wire one is broken and leaking oil and the one wire one is missing the wire, so I need to replace them both and figure out where the wire is/ goes to on that one with 1 wire

[DaveVA78Chieftain]

On the attached diagram:

oil pressure switch is circuit 31

oil pressure switch is on page 1

oil pressure gauge is on page 2

[MotorPro]

You may not need to replace it. You need to hook up the wire.

[cncsparky]

Also, if you want to test your gauge and wiring, you can ground the sensor (the single wire unit) wire to the engine block with ignition power on.  You should see the oil gauge swing full scale if its working ok.

[M & J]

Part of her problem is she can't find the wire that goes to the sender.

[DaveVA78Chieftain]

Unfortunately, my 84 book only shows point to point wiring connectiopns.  It does not show wiring harness routing like the 90's era books do.  The only thing I can offer is to open the front access hood and look on the drivers side bulkhead for the bulkhead connector shown on that PDF file I attached in my previous post.  She would need to locate the pin for circuit 31 (tan approx 18 gauge wire) and then either attach a new wire from there to the sending unit or walk the cable run hand over hand down to the sender unit to locate where it was broken off.  Yes, that would require opening up the bundle to locate the offending wire at several points along the way back down to the sending unit.  The PDF diagram of the connector should look very similar to the actual connector.

Dave

[moonlitcoyote]

Thanks, I'll look into it tomorrow  had to get other stuff done today.

the hardest part about those diagrams is the fact that they dont show you a picture and tell you EXACTLY where the wire starts. .. Something like, under dash connector on left with 10 wires coming out.. You know something that gives you an ACTUAL starting point. I can see the connectors in the diagram and how they come out and go to another connector, but finding the first connector is the problem.

[DaveVA78Chieftain]

Will see if my 1990 book has some sort of a pic that will work when I get home

[DaveVA78Chieftain]

MJ,
First my understanding is that the oil pressure senders are located at the drivers side front of the engine, behind the PS pump just above the oil pan like depicted in Handy Dans post (http://www.classicwinnebagos.com/forum/index.php/topic,6292.msg25323.html#msg25323)



Based on what I see on this drawing:


The oil sender lead of the engine wiring harness (item 83) is routed from the sender up the front of the engine and back down the drivers side of the intake manifold.  You should find the tan wire for the sender in that wiring harness.  I would not expect it to be completly gone.

Dave

[moonlitcoyote]

Thank you Dave, I will see what I can find. Probably tomorrow since its going to be raining so I cant do much anything else.

[DaveVA78Chieftain]

When the tan wire is removed from the sending unit, the dash gauge should read max pressure
When the tan wire is removed from the sending unit and then attached to ground (shorted to ground), the dash gauge should read minimum pressure

[moonlitcoyote]

That helps Dave, does the engine have to be running or the key just turned on in order for the gauge to move?

[DaveVA78Chieftain]

For that test just key on

You said the wire is not connected and you are having problems finding it so most likely just getting it wired back up will solve your problem

[moonlitcoyote]

Question.. I found the wiring harness that goes to the 2 wire sensor (still dont know the name of it) would the wire I'm looking for be in with those?

[DaveVA78Chieftain]

All I can is open it up a foot or so away from the end to see if it is in there.  I have no way of knowing the exact answer to your question.  No need for a big hole in to just peek inside.

Dave

[moonlitcoyote]

thanks, I did that but there are only 3 wires and I followed them all the way to where they go and that wasnt it. I cant believe the wire is gone, I expected it to be hanging there somewhere