oil pressure gauge

[brplut40]

The other day I went out on the boat and noticed no oil pressure, so I immediately killed it. I waited a little while and check the oil, full. So I figured the gauge had gone bad and went about my way. The boat ran fine all day, so there was actually oil pressure, otherwise it would have blown up I got a new gauge last night and am putting it in now. It still shows no pressure. I still have plenty of oil. I have a good ground, good constant 12v, and the signal various in voltage as the rpms change. I took a ready with a volt meter at what I thought was the sending unit, on the top back of the intake manifold. The voltage changes with rpm, same as at the gauge, which should indicate no cut in the wire. What am I missing. I really need to know if the oil pressure actually does go out. Thanks

 

[jerryjerry05]

Re: oil pressure gauge

Sounds like a bad connection someplace.The sender should have a blue wire to it. Hook up the guage and ground it out. It should peg the needle. If not it's possible it's bad. Look for a bad ground somewhere.Jerry

 

[brplut40]

Re: oil pressure gauge

when all i hook up is the ground and signal wire, directly off the sending unit, it pegs the gauge all the way to the left, below zero. I ran wires from the battery, positive and negative, and from the sending unit, all direct and it still did not work, it moved from the pegged position, but still below zero.

 

[bomar76]

Re: oil pressure gauge

........... I waited a little while and check the oil, full. So I figured the gauge had gone bad and went about my way. The boat ran fine all day, so there was actually oil pressure, otherwise it would have blown up I got a new gauge last night and am putting it in now. It still shows no pressure. I still have plenty of oil.

Just so you know.....
an oil pressure gauge measures oil pressure, not oil level...
your pan can be full and have no oil pressure due to a pump drive faliure, pump failure, clogged screen, pickup falling off pump, etc.

Since you ran it the boat all over the place and the engine didn't sieze or grenade you must of had at least some oil pressure, but looking at the dipstick didn't indicate pressure was OK.

Buy a mechanical gauge and TEMPORARILY hook it up and see what your oil pressure really is. Do Not leave it hooked up permanently as the little tube WILL break and blow the contents of your oil pan all over the bilge.

 

[brplut40]

Re: oil pressure gauge

Does anyone know if the post coming off the sending unit should be a grounding point? I know the sending unit grounds out through the engine block. If I take a multimeter and hook the positive up to the positive on the battery and the negative to the post on the oil sending unit, should I get some type reading? I thought that was how the gauge and sending unit work.

 

[brplut40]

Re: oil pressure gauge

Here is the final solution. I changed the oil pressure sending unit and everything worked fine. Included with the new sending unit were some specs that I wanted to share. They are resistance readings for the sending unit based on oil pressure. they are as follows:

0psi = 240 ohms
40psi = 103ohms
80psi = 33ohms

Make sure you remove the single wire from the sending unit when testing the resistance. These readings are for a teleflex oil sending unit. I put it on my 4.3L vortech v6 mercursier.