Oil pressure gauge pegged

Stock FSJ Tech Area
candymancan
Posts: 1791
Joined: Tue Mar 22, 2016 11:32 pm

Oil pressure gauge pegged

Postby candymancan » Sat Jul 14, 2018 7:11 am

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 ?
2013 SS camaro, cammed, and modded too much to say 500 RWHP/650 crank 30k
1998 Jeep Grand Cherokee 5.9L Limited 191k
1998 Jeep Grand Cherokee 4.0 I6 laredo 256k
1990 Jeep Grand Wagoneer 126k

SJTD
Posts: 1007
Joined: Tue May 21, 2013 12:02 pm
Location: Lompoc, Sunland or somewhere between

Re: Oil pressure gauge pegged

Postby SJTD » Sat Jul 14, 2018 7:25 am

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

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.

Herk
Posts: 183
Joined: Mon Mar 25, 2013 8:14 pm

Re: Oil pressure gauge pegged

Postby Herk » Sat Jul 14, 2018 7:30 am

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.

candymancan
Posts: 1791
Joined: Tue Mar 22, 2016 11:32 pm

Re: Oil pressure gauge pegged

Postby candymancan » Sat Jul 14, 2018 8:10 am

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 ?
2013 SS camaro, cammed, and modded too much to say 500 RWHP/650 crank 30k
1998 Jeep Grand Cherokee 5.9L Limited 191k
1998 Jeep Grand Cherokee 4.0 I6 laredo 256k
1990 Jeep Grand Wagoneer 126k

User avatar
kansasboy001
Posts: 159
Joined: Tue Jan 31, 2017 1:47 pm

Re: Oil pressure gauge pegged

Postby kansasboy001 » Sat Jul 14, 2018 8:33 am

On 1986+ the guages peg when un pluged. If its interminatly pegging you have a short in the wire somewhere.
1983 Cherokee Laredo. 360/ 727/ np229/ Rochester quadrajet/ Msd ignition

candymancan
Posts: 1791
Joined: Tue Mar 22, 2016 11:32 pm

Re: Oil pressure gauge pegged

Postby candymancan » Sat Jul 14, 2018 11:34 am

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
2013 SS camaro, cammed, and modded too much to say 500 RWHP/650 crank 30k
1998 Jeep Grand Cherokee 5.9L Limited 191k
1998 Jeep Grand Cherokee 4.0 I6 laredo 256k
1990 Jeep Grand Wagoneer 126k

User avatar
babywag
Posts: 1028
Joined: Fri Jun 08, 2012 7:29 pm
Location: Land of Fruit Loops & Coconuts

Re: Oil pressure gauge pegged

Postby babywag » Sat Jul 14, 2018 1:27 pm

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.
-Tony
'88 GW (aka Babywag) '90 GW (aka JunkBucket) both fuel injected.


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