oil pressure gauge/ ground question

[gchappel]

I have been having intermittent problems with my starter which we have been trying to track down. It isn't the starter, ignition switch, battery, etc----so I decided to add an extra ground strap from the tranny to the to the tub. I don't know if that helped my starter problem at all, because it only fails every 3 months, so it will be a while. After adding the 2nd ground strap my oil pressure gauge is reading a little higher than before--now reads 4.5 instead of 4 at 3000 rpm. It is a slight but definate change. Could improving the ground somehow change the meter reading? If so possibly it confirms a bad ground back there somewhere.
Thanks
gary

[ischmitz]

You oil pressure sender sends an attenuated ground signal (engine ground) back to the meter against battery +12volts. If you disconnect the sender the instrument should read zero. If you short the lead on the sender to the engine your instrument should peg at the top.

A poor ground strap from the engine to the body/battery adds another resistor between the engine and the battery. Depending how bad it is the battery ground is not at 0 volts but something higher. It also would cause the oil pressure instrument to read higher if anything. That's oppositve from what you see, right?

In any case I would measure the voltage between the engine case and the body with a sensitive DVM. If there is any voltage other than zero you have a bad ground strap. Next make sure there are no corroded connectors on the oil pressure sending unit, the gauge, and the 14-pin connector.

Ingo