Stuck Oil Pressure gauge
Thread Starter
Cruising
Joined: Jun 2019
Posts: 12
Likes: 0
Stuck Oil Pressure gauge
I have a 1979 Corvette that I purchased middle of 2019. The oil pressure gauge seems to be stuck at 40 PSI; it never fluctuates regardless. Key off, running, idling, revving, etc. it is at 40 PSI. The sending unit looks new. I have not tested it any further. Any thoughts on where to go from here?
Safety Car
Joined: Dec 2007
Posts: 4,229
Likes: 39
From: Beautiful East Texas
Mine was stuck too when I got the car... tried two different "GM" replacement parts gauges from different vendors and both gauges were
bad. (and a real PITA to change out)
I went back to my OEM gauge, cleaned it up following a Wilcox instructional video and got it working again...
but.... mine is a mechanical gauge (1973) while yours is likely electrical.
mardyn
bad. (and a real PITA to change out)
I went back to my OEM gauge, cleaned it up following a Wilcox instructional video and got it working again...
but.... mine is a mechanical gauge (1973) while yours is likely electrical.
mardyn
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Either the oil pressure feed line to the gauge, or the gauge itself, probably has a solid plug of caked oil blocking normal oil passage/flow. CAREFULLY remove the oil feed line to the gauge at the engine and use compressed air to blow pulses of air into that line. To not put more than 80psi air pressure into that line. Doing that a few time will likely clear any minor plug.
If that does not FIX the problem and/or you see no movement on the gauge when you put the air to that line, the dial/rack mechanism inside the gauge is likely locked up. In that case, you need to replace the gauge. My estimate of probability of fixing your problem with the pressurized air is about 50%. So that testing is justified as it excludes dash disassembly and gauge costs.
Take care with that oil feed line. Whether it is metal tubing or plastic tubing, it is OLD and probably much weaker (and brittle) than it was originally.
If that does not FIX the problem and/or you see no movement on the gauge when you put the air to that line, the dial/rack mechanism inside the gauge is likely locked up. In that case, you need to replace the gauge. My estimate of probability of fixing your problem with the pressurized air is about 50%. So that testing is justified as it excludes dash disassembly and gauge costs.
Take care with that oil feed line. Whether it is metal tubing or plastic tubing, it is OLD and probably much weaker (and brittle) than it was originally.
Melting Slicks
Joined: Mar 2005
Posts: 2,095
Likes: 299
From: Midlothian VA
Either the oil pressure feed line to the gauge, or the gauge itself, probably has a solid plug of caked oil blocking normal oil passage/flow. CAREFULLY remove the oil feed line to the gauge at the engine and use compressed air to blow pulses of air into that line. To not put more than 80psi air pressure into that line. Doing that a few time will likely clear any minor plug.
If that does not FIX the problem and/or you see no movement on the gauge when you put the air to that line, the dial/rack mechanism inside the gauge is likely locked up. In that case, you need to replace the gauge. My estimate of probability of fixing your problem with the pressurized air is about 50%. So that testing is justified as it excludes dash disassembly and gauge costs.
Take care with that oil feed line. Whether it is metal tubing or plastic tubing, it is OLD and probably much weaker (and brittle) than it was originally.
If that does not FIX the problem and/or you see no movement on the gauge when you put the air to that line, the dial/rack mechanism inside the gauge is likely locked up. In that case, you need to replace the gauge. My estimate of probability of fixing your problem with the pressurized air is about 50%. So that testing is justified as it excludes dash disassembly and gauge costs.
Take care with that oil feed line. Whether it is metal tubing or plastic tubing, it is OLD and probably much weaker (and brittle) than it was originally.
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Michael S. Palmer
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Sorry. Missed the fact it was a '74. An electric gauge will read a constant value if it gets NO signal or if there is a constant pressure on it (highly dubious). It can also be because one of the armature wires inside the gauge has lost electrical contact. In that case, wherever the gauge was when it failed is where it will stay (unless serious bump or vibration causes it to shift a bit). Most likely possibilities are loss of 12vdc power to the gauge or bad gauge.
Team Owner
Joined: Sep 2002
Posts: 38,369
Likes: 2,085
From: California
Do you know what oil pump was installed. If you have like the Solid lifter Z-28 or Vette 65-70 lbs oil pump unit (One reason I like the 80lb gauges)! It may never move when running. Pull the valve covers and see if oil spraying all over from each push rod.
Last edited by TCracingCA; Jan 16, 2020 at 01:12 AM.
Safety Car
Joined: Dec 2007
Posts: 4,229
Likes: 39
From: Beautiful East Texas
Test the system first by disconnecting and grounding the wire to the oil pressure sensor... key on, it should move the gauge, if not pull the center
gauge cluster (which is a major PITA on my '73) and test the oil pressure gauge connections for voltage and ground and continuity to the pressure sensor.
If you've got all of these and the gauge still fails to move, replace the gauge.
It's not that complicated, but just time consuming to get that cluster out and apart if necessary.
Good luck
mardyn
gauge cluster (which is a major PITA on my '73) and test the oil pressure gauge connections for voltage and ground and continuity to the pressure sensor.
If you've got all of these and the gauge still fails to move, replace the gauge.
It's not that complicated, but just time consuming to get that cluster out and apart if necessary.
Good luck
mardyn
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
I took my 78 L48 out yesterday afternoon to stretch its legs and the operation of the oil pressure gauge seemed erratic. It would settle just above 20, would tick up toward 40 as the car accelerated. At a constant 50 mph, it showed a pressure of around 30-35, which seemed low but ok. But it was the erratic movement of the needle that was disconcerting. Anything here I should worry about or check? Its a stock motor, no cam, no mods, just stock 185 mph. Runs great for what it is, starts without complication as always, a few pumps of the gas pedal and fires up.
Instructor
Joined: Feb 2011
Posts: 177
Likes: 9
From: Elizabethtown Pa
I have been dealing with a non functioning oil gauge. First installed a new sending unit, as it was easier than getting into the dash and they cost $25.00. Didn't help. Bought a new gauge and it
did as Wilcox states above in this thread; but sending unit not working. Examined sending unit and that little bity hole had gotten plugged with something. Used a welding wire nozzle cleaning rod and now works fine.
Remove and clean the sending unit hole first, will save you time, money and frustration.
did as Wilcox states above in this thread; but sending unit not working. Examined sending unit and that little bity hole had gotten plugged with something. Used a welding wire nozzle cleaning rod and now works fine.
Remove and clean the sending unit hole first, will save you time, money and frustration.
