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The oil pressure on the dash keeps pegging sometimes.. put the key in turn to power and its pegged.. I tried unplugging the thing at the sending unit and its still pegged... wiggle the wires still pugged.. Unplug the fuse i put in line.. still pegged.. and i know the fuse is working as i can hear the little plunger on the throttle body disengadging and re engadging when i put it back in..

Then randomly itll stop pegging on its own.

Any ideas ?

My WAG is a bad sender. Check the resistance between the sender and block.

Bad sender or dead short to ground in the wire. All gauge sending units switch on the ground lead, so if the sender wire is connected straight to the chassis the gauge should swing full scale (hot engine, full tank or max pressure). Keep this in mind if you ever want to test a gauge.

If the sender ie bad why would it pegg if unplugged. Like ill unplug it. turn thr key to power abd it will peg. And why is it doing that if i unplug the inline fuse.. The orange wire leads to 3 location sending unit. a.c i think and the nipple thing on the choke... with no power why would it still peg ?

You saying the sender wire is grounded to the block ?

On 1986+ the guages peg when un pluged. If its interminatly pegging you have a short in the wire somewhere.

Hrmm well the wire is only like a foot long. But it merges together with 3 others.. Guess ill have to pull the wire outa the harness and check it out.

Youd figure if it were shorting it would pop the inline fuse though... ? And why does it do it when the fuse is unplugged.. it shouldnt be getting any power then..

Wouldnt this mesn its actually the sender going bad.. because you said if unplugged it peggs.. So then no power via remove the inline fuse i put why is it pegging then ? To me that means the oil pressure sender is bad.

But ill check the wiring. Going to see how much a new sender is too

it’s not “shorting”, high resistance = open circuit or break in wire.

‘86-‘91 high resistance = pegged gauge
anything over ~90ohm

very common for gauge cluster pin to break free from circuit board too.