The fabulous jumping oil pressure needle...

[rennch]

Hi all,

I've got an odd problem. My oil pressure needle is jumping all over the place while I'm driving. I'm not sure if it's a gauge problem or an oil pressure issue. The car is a 72 with a 3.0 from a 1979 motor.

What's the best way to test whether it's the pressure or the gauge?

Thanks in advance.

mto

[Tim Walsh]

Stick a mechanical guage on it and that should eliminate the whole sender question.

[rennch]

Barring that, what are my other options?

[masraum]

Well, you could put an ohm meter on the thing and determine if the resistance is all over the place. Generally a jumpy gauge indicates a bad connection or a faulty sender.

[rennch]

I'm an electronic neophyte...any chance you could detail what I should do with my trusty meter?

Thanks.

[Early_S_Man]

Could be loose or dirty connection at sender, or cracked wire making intermittent connection ...

To test gauge and wiring, take connector loose at sender and ground it with ignition on ... if gauge reading settles down to a stable zero reading, then you don't have a gauge or wiring problem. Try substituting a 1000 Ohm potentiometer for the sender ... sweep full range, and the gauge should do the same. Crimp both sides of the sender Faston connector slightly after cleaning ... to put more tension on the tab cannection.

[ischmitz]

Warren should be right on the money, I had the same with the 2.7. A new spade connector crimped to the wire and it was rock solid.

Ingo

[1bar]

Not to sound like an echo, but I had exactly the same problem. The spade lug on the sender was loose. Either bend the fingers back (tighten it up with a pair of pliers - it worked for me) or replace it.

[Wil Ferch]

Or...it might be behaving exactly as it should...

at idle...you'll see normal level.

When off-idle and running...it'll drop into the red zone.

As you speed up and down...it'll go down and up..

What's it doing at a steady idle?

---Wil Ferch

[rennch]

no...it's peaked at 140. It jumps drastically at idle, and as I drive, it just pins it at 140. It hasn't always done this...I just had some stereo gear installed, so I think there's something up with it.

[Emission]

Check the spade connector. I had the same issue.

[Wil Ferch]

My money is on bad ground...
---Wil Ferch

[rennch]

I think it's probably a bad ground too, because my voltage gauge isn't working either, at the moment.

[Tim Walsh]

whoops.. sorry emptyo... my previous post sounded like just do away with the VDO gauge and use a mech. one.. I meant use a mech. one to make sure it's not instrument error. If it doesn't jump around then go onto the next part of the system, the sender. I haven't done this step but I would stick a resistance gauge between the sender and a known good ground. If that seems to send a good signal (resistance is directly proportional to the oil pressure or RPM) then go onto the next thing, the line between your guage and the sender. I would test for that same signal at the wire between the sender wire at the guage. If that gives a good signal try a new gauge.

[Leland Pate]

Mine was doing the same thing.
I used some dikes and crimped the connector to make it fit tighter around the spade on the sender unit.
Now, it doesn't jump anymore.
Good luck,
Lee

[rennch]

My sender unit would be just east of my fan, no?

[Leland Pate]

Yup, it sits just to the right of the fan shroud.
There is one spade connector on top of the sender.
Clean, and slightly crimp the connector and see if your problem goes away.

[rennch]

Thanks Doc. I'll check 'er out.

mike

[rennch]

Ok, I'm fixed. It turns out the solder had broken on the tab that connects to the switch. I fired some fresh solder in there, and it seems like it's going to be ok.

Thanks all!

[98GTW]

There's another possible cause for a jumping oil pressure needle, as I discovered last Thursday.
Mine wasn't pegging, only jumping erratically around its normal reading. I've driven ~400 miles since bring it out of winter storage, where the oil was changed from synthetic back to dino oil, and I thought that might be related.
Just to cover all the bases, I checked the oil level Thursday night. It was low, so I added a quart (the last one in my garage). Still low, so I buzzed out to the local parts store and picked up another case and put in another quart. ... Still low, starting to make me nervous, so I added another quart (That's three, if you're counting). ... Still not showing on the dipstick, and I'm questioning whether someone traded my dipstick for a short one....The fourth quart finally showed itself on the stick, but still below the MIN line. The fifth quart brought me up to the midpoint between MIN and MAX.
The oil pressure needle isn't jumping any more.