Engine stubbles at idle speed

enblethen wrote:
The fuel pump sending unit has three wires not one.
oil pressure sending unit
As for testing, it is hard to verify that the contacts are not pitted to the point of increasing resistance that causes the voltage drop.
I noticed that my oil pressure gauge had changed slightly indicating higher oil pressure. I changed the sending unit and the gauge started registering closer to where it was.
The fuel pump relay only operates to pressurize the system. It does not operate under normal pump operation. It runs for 2 to 10 seconds when ignition is first turned to "on".

. Thanks Bud, I also put my fingers on the relay and can't feel any clicking, are you saying that the oil pressure sending unit controls this relay? I could not open the link you sent me, but what I think is the sending unit is about 1 in in Dia and 3 ins long and has about 5 wires attached to it.