Oil pressure gauge
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
You either have a loose connection somewhere on the sender "signal" wire, or that wire is nearly fatigued through somewhere along its path. The connection at the gauge is unlikely to be the problem; its more likely to be in the engine compartment somewhere.
Former Vendor
Joined: Aug 2006
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Could be a printed circuit... but probably the sending unit or a connection issue at the sending unit.
If you pull the dash, the picture below will show you which terminal to look for.
If you pull the dash, the picture below will show you which terminal to look for.
Le Mans Master
Joined: Sep 2004
Posts: 5,116
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From: Livonia MI
This isn't something to take lightly. I'd at least temporarely install an undamped mechanical gauge, to see what's really going on. Maybe tee into the existing, for comparison. Possibly a rod bearing going bad, and something you're wanting to know about right away.
Team Owner
Joined: Jun 2001
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From: Thomson Georgia
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
True and a good idea.. That reminded me of a customer that called here years ago and told us about his car purchase.. Everything worked but the oil pressure gauge. On the way driving down here he found out the gauge was indeed working.
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Thanks Wilcox and everyone for your help and guidence.I am still with no results working on my more serious problem of the code 42 (a 1982 problem)but then it's on to the oil sending switch.I did not think this electronic spark control problem was going to take 2 solid weeks to diagnose.The car runs good but the darn light (check engine) will not go off so this weekend it is back into the wiring.Persistance will pay off.I do have the faith!
Cruising
Joined: Aug 2005
Posts: 10
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From: atlanta ga
oil pressure gauge and code 42 coninues
Thanks Wilcox and everyone for your help and guidence.I am still with no results working on my more serious problem of the code 42 (a 1982 problem)but then it's on to the oil sending switch.I did not think this electronic spark control problem was going to take 2 solid weeks to diagnose.The car runs good but the darn light (check engine) will not go off so this weekend it is back into the wiring.Persistance will pay off.I do have the faith!
On the code 42, replaced the ignition module on a suggestion from a friend, no help. Then, again followed the flow chart in the shop manual and it tells me there's a short in the ground somewhere....but where do I start looking? Help; car runs good but the mileage is better without the code 42...BTW been running regular gas for years and it runs fine. 26-30 mpg hiway w/o the code 42; 20-26 with the code 42
Last edited by violinsib; Jan 22, 2017 at 02:05 PM.
Le Mans Master
Joined: Oct 2006
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
If you have the GM shop manual, it has the diagrams all laid out showing connectors and grounds. You just have to track the wire thru all of it's connectors. Could be as simple as one has shaken loose. Or a ground got a little crusty.
Melting Slicks
Joined: May 2015
Posts: 2,365
Likes: 428
From: Cape Girardeau Missouri
From what I've read here those mechanical oil pressure gauges contain some oil that slightly dampens the needle movement. If some or all of the oil leaks out the needle can begin to jump very rapidly.
I have the same problem in my '79 especially when coasting. Replaced the sender--to little or no effect. Connections are all good and the PC is new (due to other problems). I have the gauge pack out for some electrical updates and plan to replace the gauge.
I have the same problem in my '79 especially when coasting. Replaced the sender--to little or no effect. Connections are all good and the PC is new (due to other problems). I have the gauge pack out for some electrical updates and plan to replace the gauge.
Last edited by SwampeastMike; Jan 22, 2017 at 06:07 PM.
Le Mans Master
Joined: Dec 2006
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From what I've read here those mechanical oil pressure gauges contain some oil that slightly dampens the needle movement. If some or all of the oil leaks out the needle can begin to jump very rapidly.
I have the same problem in my '79 especially when coasting. Replaced the sender--to little or no effect. Connections are all good and the PC is new (due to other problems). I have the gauge pack out for some electrical updates and plan to replace the gauge.
I have the same problem in my '79 especially when coasting. Replaced the sender--to little or no effect. Connections are all good and the PC is new (due to other problems). I have the gauge pack out for some electrical updates and plan to replace the gauge.
Cruising
Joined: Aug 2005
Posts: 10
Likes: 0
From: atlanta ga
From what I've read here those mechanical oil pressure gauges contain some oil that slightly dampens the needle movement. If some or all of the oil leaks out the needle can begin to jump very rapidly.
I have the same problem in my '79 especially when coasting. Replaced the sender--to little or no effect. Connections are all good and the PC is new (due to other problems). I have the gauge pack out for some electrical updates and plan to replace the gauge.
I have the same problem in my '79 especially when coasting. Replaced the sender--to little or no effect. Connections are all good and the PC is new (due to other problems). I have the gauge pack out for some electrical updates and plan to replace the gauge.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Have you removed/cleaned/replaced the connectors on your ECU? Especially check any ground wires going to the ECU. Sometimes those can get a bit corroded or loose, causing problems. Might not help, but its a good thing to do; at least it will eliminate one possible fault. {Maybe eliminate the #42 codes.}
An electrical oil pressure sender is merely a variable resistor between the sender line and 'ground'. If you remove the sender wire and stick a 50 ohm resistor in its place, you can see whether the gauge reading continues to flutter (indicates that the circuit board likely has the problem) or if it becomes stable (indicating that the sending unit is bad). My suspicion is that your problem is the sending unit.
An electrical oil pressure sender is merely a variable resistor between the sender line and 'ground'. If you remove the sender wire and stick a 50 ohm resistor in its place, you can see whether the gauge reading continues to flutter (indicates that the circuit board likely has the problem) or if it becomes stable (indicating that the sending unit is bad). My suspicion is that your problem is the sending unit.
Last edited by 7T1vette; Jan 26, 2017 at 09:34 AM.