stumped by oil pressure guage

[rebars1]

18.5' 1974 IMP 255s, Ford 302: My oil pressure guage pegs when I turn on the switch and stays pegged when the engine is running. I have replaced the sender and I have tested the guage per the Merc manual (0psi off, pegged with jumper to ground from "sender" connection on on the guage.) I have also tried a new wire directly from the sender to the guage, but get the same results. The warning light comes on when I turn the key, then goes off when the engine runs. Any ideas? This is my last challenge before getting the boat in the water after a long restoration project.

 

[Don S]

Re: stumped by oil pressure guage

It's simple, the gauge is shorted to ground inside. Replace the gauge. I have replaced many that did the same thing.

 

[rebars1]

Re: stumped by oil pressure guage

Thanks, Don S. I was wondering if something like that could happen.

 

[rebars1]

Re: stumped by oil pressure guage

Thanks, Don S. I was wondering if something like that could happen.

 

[rebars1]

Re: stumped by oil pressure guage

Thanks, Don S. I was wondering if something like that could happen.

 

[I/O WALDO]

Re: stumped by oil pressure guage

Does the gauge peg with the key on and nothing connected to the sender terminal?

 

[rebars1]

Re: stumped by oil pressure guage

Well, I replaced the guage and replaced the sender, again. I tested the sender with another guage connected with jumpers directly to the sender and battery. It read to just below the 80 psi level. I then tried the new guage in the dash after double checking and tightening the ground wires. It did not peg, but was just below the 80psi level also. I was expecting 40-60 psi at idle. Does the high reading indicate a problem?

 

[Don S]

Re: stumped by oil pressure guage

Get a mechanical gauge and hook it to the engine temporarily and verify what the oil pressure is actually doing.

 

[lilmandavis]

Re: stumped by oil pressure guage

could it be a wire shorted out somewhere?

 

[rebars1]

Re: stumped by oil pressure guage

I attached a mechanical oil pressure guage and got a reading of about 52 psi at idle. Before installing the guage and after attaching the small nylon tube that came with it to the engine, I ran the engine for a few seconds until there was a good flow of oil through the line. I then attched a remote electric guage to the sender with jumpers to the battery and got a reading of about 40 psi, with a little increase up to 1500rpm. When I re-attached the bvoat wires to the dash guage, I got similar readings (40psi @ idle with upward movement with rpm increase.)

 

[rebars1]

Re: stumped by oil pressure guage

I guess there was some blockage in the pipe or something that opened up when I let the oil flow through the tubing.

 

[cobra 3.0]

Re: stumped by oil pressure guage

My oil guage would read a very low oil pressure at idle. On my next oil change I added a valve lifter cleaner product. The oil pressure guage must have been cleaned by this product because it now reads correctly. Go figure!

 

[Bondo]

Re: stumped by oil pressure guage

That's 1 of the Projects I've never gotten too,.......<br /><br />Mounting a permanent Mechanical Water Temp,+ Oil Pressure gauges in the engine bay, or On the engine...........<br /><br />Someday..........

 

[rebars1]

Re: stumped by oil pressure guage

I suppose one could install a "T" fitting and have both the dash guage a mechanical guage on the engine?

 

[rebars1]

Re: stumped by oil pressure guage

Interesting story, cobra3.0