My stock oil pressure gauge was fluctuating and i had the sending unit replaced, why doesn't my gauge work now?

Question

Got an Autozone (Duralast) oil pressure sending unit and put in it and now my oil pressure comes up to normal when i crank it but goes to rock bottom when the truck starts, any suggestions?

Answer 1

That's a bad sending unit. Take it back and get another brand or go to the dealer. Personally I'd put the original one back in, the fluctuation wasn't a bad sending unit, it's more likely fluctuating oil pressure.

Answer 2

There are TWO general types of oil pressure sending units.



One is a normally-closed switch, for an idiot LIGHT.



The other is a variable resistor, for a GAUGE.



It sounds like they gave you the sending unit for an idiot light.



-Engine overhaul mechanic and general automotive mechanic since 1972

Answer 3

Try touching sender wire to ground when it starts. If it comes up , your sender is bad.



Double check by borrowing a mechanical gauge that fits same hole. Exchange it for the sender, your oil pressure May fluctuate. Old sender might be ok, you may have a stuck open bypass valve, clogged filter, Low Oil. Check oil level, Top off. Replace filter. If mech gauge still says bad, change to a good detergent oil. It might loosen stuck pump bypass. If not, remove pump and check. Maybe broken spring. Often they can be reversed and you can put flat ends together, work just fine. Broken springs can nest together and act like one short, tight spring.

Answer 4

You need to have a mechanic check your oil pressure. Here's what you can do yourself, check all the fuses and replace bad ones and tighten up the wire's plug on the oil pressure sender.

Answer 5

On my LS5300 truck engine there is a tiny thimble size filter screen under the oil pressure sender that gets plugged up and caused the problem on mine. The screen is down inside the pressure switch cup.



On my truck the sender was still good but the filter screen was plugged up, new screen and sender.

Answer 6

Wrong sending unit?

You may have a bad ignition switch and it's only giving power to the gauges in the crank/start position.

Anything else not getting power?

Check for broken wires at the sending unit harness connector.

Answer 7

go to a garage & they can put another gauge on the engine and compare to two readings ...............