I have a 29' Fountain with twin 454 Mag MPIs and my oil pressure gauges stay pinned as soon as I turn the key. I changed the oil pressure sending unit, but the gauge still goes from zero to pinned as soon as i turn the key. I am thinking there is a bad ground, but I am wondering if anyone else has had this problem before and what they did.

I think you may have a short to ground in the sender wiring cause if you ground the sender wire the guage should peg

Actually the wire going from the sending unit to the gauge may be grounding somewhere in between. Try disconnecting it and start it and see if still does it. If it does than either the wire is grounding somewhere or it is in the gauge it self.

That was my thought, I would check the guage & wiring by grounding the lead at the sender.If you unhook the lead & turn the key it should read zero if not check wiring. you can check guage the same way by grounding the sender lead. I have found chaffed insulation around studs or other sharp edges

If you used sealer on the sender, it may not be grounding properly. The sender grounds itself to the engine block. It could also be bad ground on the back of the gauge.

Thanks for the feedback. I will let you know what I determine.

If you changed gages you could have the wrong polarity sending units.

x2 it must be a short, a open would be "0" psi.

That would depend on if the gage is sinking or sourcing.

all the above!!

did you have any stereo work done??? i have seen some people ground a head unit to the gauges and hooked to the wrong wire..ma be put speakers in with 3'' drywall screws and through a wire harness....i have seen a bunch of weird mishaps..