Oil Pressure Gauge Jumping

[69fourspd]

Getting a bit frustrated with my Oil Pressure Gauge and I dont like running the car without knowing I have good pressure for sure.  Motor is a 440 which is fresh and have verified I have pressure with a mechanical gauge.  Here is what I have done:
- New Sending Unit - this is the second one actually.  Fat one for pressure, not dummy light.
- New Voltage limiter - all other gauges work fine.
- New Oil Pressure Gauge from Y/O. old one did the same thing

Symptoms:
Gauge jumps very quickly every second or so.  Looks like a clock ticking. Does this with key on and not running as well as when running.  If I ground the wire to the sending unit, it continues to jump, but pegs the gauge from 0 to full. When the wire is on the sending unit, it jumps from 0 to about 20.  When the car is running, it jumps from 0 to about 40. If the wire is not grounded and off the sending unit, gauge does nothing.  When you turn the key to on or accessory, the gauge moves all the way up very smooth, then drops back to 0 and starts the "ticking".

Engine is grounded to firewall well. All new wiring/harness.

I am pulling my hair out. Any ideas??? Someone has to have had an issue like this in the past right??? Any help is much appreciated.

[b5blue]

Find the bulkhead connection and clean.

[Ghoste]

And put a little dielectric grease in there after you clean it.

[Dino]

Yes check the wire, gray wire going to slot K, middle bulkhead connector bottom row second from the left.  It could also be an issue with the circuit board I suppose.  The pins on mine looked fine but I still had continuity issues until I soldered them to the board.

[b5blue]

Very good idea, the pins on the PCB for gauges. 

[69fourspd]

Thanks for the suggestions and advice.  That will be the next thing I try.  Will let you know how it goes.

[69fourspd]

Took the suggestions and cleaned up the bulkhead connector and harness that connects to the back of the cluster.  Same issue - gauge still jumps rapidly.  Any other ideas?

So I can drive the car and feel a bit better about the situation, does anyone know of an aftermarket oil pressure gauge which will work with an original style one wire sending unit? I am thinking I could just run a wire off the factory wiring where the gauge wire comes in. Its just a ground, so I dont see many issues doing it this way.  It is at least piece of mind until I can get my factory gauge working properly. 

Any suggestions would be great.  Thanks!

[b5blue]

For peace of mind put a manual oil gauge on it, the one with the tube. Cheap and easy.