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No oil pressure or guage not working?


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75 280 with 79 block and N42 head, head has been refreshed, cleaned up and valve's done, new head gasket, no oil leaks apparent anyhwere. Now I have no oil pressure showing on the guage. I pulled the valve cover with the engine running (not smart) and oil was flying all over the place, replaced the oil sending unit and still no pressure indicated. The guage worked prior to the engine removal. I'm not sure if there is no oil pressure, bad guage, sending unit or what? I've checked electrical continuity from sending unit to the connector in the engine bay and its OK, haven't been able to check from the connector to the guage. Also tried grounding the wire from the sender with ignition on and no movement of the guage at all.

Edited by mjr45
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You will need to attach the hand held mechanical oil pressure gauge to the sender's port and test it. Once you confirmed that there is oil pressure, you will go to the electrical oil pressure gauge inside your car, identify the wire that sends resistance to the gauge, put your multimeter on it and see what readings you are getting.

If there is proper resistance, you can confirm that this is indeed your electrical gauge that failed.

On my 76 I was getting the right resistance, but the gauge was bad. I installed an autometer's sender + gauge and am getting the right readings. The stock gauge was very inaccurate (basically, it will show 'low', 'middle' and 'high'). If you take an aftermarket route, don't forget to order the right adapter for the sender (BPT to NPT).

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First ground the connector on the yellow lead that connects to the sender and see if you dash gauge pegs at max pressure. (key in RUN position, engine not running). If it does, then the gauge is fine, sender is suspect. If not, look for electrical stuff. Try the fuses first. Also check wire crimp on the barrel connector for the sender on that yellow wire. May be broke off or just about broke inside the clear boot that you can't see. I see you did the ground thing, points toward gauge power issues.

Oil going everywhere with cam cover off means you have some oil pressure. No need to panic yet.

Edited by zKars
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Put the key in the run position. Put the positive lead of your meter on the wire that goes to the sending unit (with the unit unplugged). Put the negative lead on a chasis ground or negative battery terminal. You should see some voltage. It probably won't be 12 VDC, but I would not be surprised if it's around 9 volts.

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