Oil pressure gauge goes to zero

[Bleep Bleep]

Oil pressure gauge reads normally each time when the engine is started - cold and at temp. Reads pressures for a few minutes, and readings in normal range.

After a few minutes gauge goes to zero and stays there. Put a new sending unit in today. No change. Interestingly, the unit came with some type of white thread sealer? Could it be a poor ground issue? Should it be removed? Or just a **** sender?

Has anyone had the similar issue? ‘70 charger U code w/rallye dash gauges if that’s relevant?

Ideas where to look next? Thanks.

 

[dadsbee]

Stop f'n around and screw in a mechanical gauge fitting.

 

[Bleep Bleep]

Yea. I don’t like the idea of a separate aftermarket gauge but I thought that might be the better solution long term. I hear the nightmare stories of leakage. I did have one on a previous car without incident tho.

 

[Dana67Dart]

Is it a factory gauge or aftermarket?

If factory, do any of the other gauges do the same thing at the same time?

If not, with the key off, ground the sender wire at the sender. Turn the key to run and watch for needle movement. Only do this for a short time, don't let the needle peg.

Assuming you don't have a loss of oil pressure.

Run the engine and with the sender wire connected move it around a little and have some one look for needle movement. The gauges react slowly so make a move of the wire and wait for 30 or more seconds with the wire in this new position. Don't again in various other positions .

Lastly you could get a 5 watt 23 ohm resister and wire it between the sender wire and a good ground. With the key in the run position it should read about 1/2 scale. Leave it that way for the same amount of time it takes for the failure to happen.

And sealer on the threads is a wives tail.

You would have to have a 1/4" of tape finger right to be a problem (slight exaggeration)

 

[rickseeman]

I had a similar problem 2 months ago. 0 oil pressure, factory gauge. It turned out to be, and this is a weird one, the battery cable, where it grounds to the block.

 

[Bleep Bleep]

Is it a factory gauge or aftermarket?

Restore some years ago. Unfortunately I don’t know.

If factory, do any of the other gauges do the same thing at the same time?

No. All other gauges function properly.

If not, with the key off, ground the sender wire at the sender. Turn the key to run and watch for needle movement. Only do this for a short time, don't let the needle peg.

The needle shows reasonable readings but only for a short time. If I restart the car after it goes to zero, the gauge operates again then goes to zero again?

Assuming you don't have a loss of oil pressure.

I believe no.

Run the engine and with the sender wire connected move it around a little and have some one look for needle movement. The gauges react slowly so make a move of the wire and wait for 30 or more seconds with the wire in this new position. Don't again in various other positions .

I’ll try this when running and after guage reads zero. The wire connector is free of any corrosion and is clean.

Lastly you could get a 5 watt 23 ohm resister and wire it between the sender wire and a good ground. With the key in the run position it should read about 1/2 scale. Leave it that way for the same amount of time it takes for the failure to happen.

If the test shows the guage does continues to read what does that mean exactly for this situation?

Thanks for the feedback.

 

[Cranky]

Yea. I don’t like the idea of a separate aftermarket gauge but I thought that might be the better solution long term. I hear the nightmare stories of leakage. I did have one on a previous car without incident tho.

Didn't read all the replies but a 'temp' mechanical gauge will tell you the truth....

 

[Geoff 2]

Remove the wire on the sender. Connect one lead of an ohmmeter to the sender terminal, other lead to ground. Start engine & watch the meter. Any change in ohms should be gradual as oil warms up & pressure drops. If this happens, it suggests the gauge is faulty. If ohm reading changes suddenly, it suggests the sender or pump is faulty.

 

[Kern Dog]

Oil pressure gauge reads normally each time when the engine is started - cold and at temp. Reads pressures for a few minutes, and readings in normal range.

After a few minutes gauge goes to zero and stays there. Put a new sending unit in today. No change. Interestingly, the unit came with some type of white thread sealer? Could it be a poor ground issue? Should it be removed? Or just a **** sender?

Has anyone had the similar issue? ‘70 charger U code w/rallye dash gauges if that’s relevant?

Ideas where to look next? Thanks.

The factory gauges do fail. I had a gauge that would read fine but then randomly drop to zero. My gauge first did this about 300 miles from home and had me worried. The engine did not knock or rattle but it still worried me.
I tried different sending units and saw no change at all with any of them.
I added a mechanical gauge and saw pressures higher than the stock gauge ever showed.
Later, I replaced my instrument panel with an aftermarket setup.
It is the gauge where your problem lies. You can buy gauges individually or have yours rebuilt. OER makes reproduction gauges, see Classic Industries or maybe a sponsor of this site for other vendors.

 

[Bleep Bleep]

Remove the wire on the sender. Connect one lead of an ohmmeter to the sender terminal, other lead to ground. Start engine & watch the meter. Any change in ohms should be gradual as oil warms up & pressure drops. If this happens, it suggests the gauge is faulty. If ohm reading changes suddenly, it suggests the sender or pump is faulty.

Thanks. Good next step.

 

[Bleep Bleep]

It is the gauge where your problem lies. You can buy gauges individually or have yours rebuilt.

The ohms test @Geoff 2 suggests will hopefully narrow the cause.
Dropping the whole panel etc to get to the guage is daunting for me anyway. At that point using a mechanical unit is at least the short term answer.

 

[Bleep Bleep]

Lastly you could get a 5 watt 23 ohm resister and wire it between the sender wire and a good ground. With the key in the run position it should read about 1/2 scale. Leave it that way for the same amount of time it takes for the failure to happen.

It reads like this test is similar but a different way to assess guage is working, than Geoff 2’s description #8?
Just an alt approach to the same diagnosis?

 

[Bleep Bleep]

I had a similar problem 2 months ago. 0 oil pressure, factory gauge. It turned out to be, and this is a weird one, the battery cable, where it grounds to the block.

Meaning just a bad ground? Loose? Corrosion?

 

[rickseeman]

Yes

 

[Bleep Bleep]

Yes

Thanks!