350 Chevy with carb 0 oil psi

[88suburbanoverlan]

Hey guys

I’m trying to troubleshoot my 350 motor oil pressure. I was just driving it and the oil pressure was perfect and right in the middle of a whole trip. I shut it down and let it sit for about an hour and when I got back in my oil pressure was at zero for my whole 30 mile trip back. I kept it at 40 mph and listened for any grinding but didn’t hear anything nor did I see any smoke.

Before I start taking shots in the dark about the oil pressure sending unit or a bad gauge, does anyone have any suggestions? I’m also having a lot of trouble locating the line to the oil pressure gauge and I’m trying to avoid taking the dash apart but if that’s what needs to be done, I can do it.

 

[nvrenuf]

FIRST, I'd buy and hook up a mechanical gauge and verify exactly what, if any, pressure you have.

I agree, without knocking, smoke, etc it's unlikely there's an actual oiling problem.

If you're working on the 88 Sub in your profile the gauge should be electrical and being TBI there will be 2 oil senders; 1 for the gauge and 1 for the fuel pump relay. I believe the locations are behind the distributor and on the lower driver side of the block, I don't remember which sender is for which function.

 

[Bextreme04]

Hey guys

I’m trying to troubleshoot my 350 motor oil pressure. I was just driving it and the oil pressure was perfect and right in the middle of a whole trip. I shut it down and let it sit for about an hour and when I got back in my oil pressure was at zero for my whole 30 mile trip back. I kept it at 40 mph and listened for any grinding but didn’t hear anything nor did I see any smoke.

Before I start taking shots in the dark about the oil pressure sending unit or a bad gauge, does anyone have any suggestions? I’m also having a lot of trouble locating the line to the oil pressure gauge and I’m trying to avoid taking the dash apart but if that’s what needs to be done, I can do it.

Sending unit is on the back of the motor behind the intake manifold. If you unhook the wire, the gauge should read zero, if you put a wire into the connector(the wiring harness side, not the sender side) and ground that wire to the block, the gauge should then max out. If the gauge doesn't change when unplugging/grounding the wire, then you have a broken wire or a problem in the circuit/gauge.

 

[88suburbanoverlan]

FIRST, I'd buy and hook up a mechanical gauge and verify exactly what, if any, pressure you have.

I agree, without knocking, smoke, etc it's unlikely there's an actual oiling problem.

If you're working on the 88 Sub in your profile the gauge should be electrical and being TBI there will be 2 oil senders; 1 for the gauge and 1 for the fuel pump relay. I believe the locations are behind the distributor and on the lower driver side of the block, I don't remember which sender is for which function.

Thank you. When I first made my profile, I was buying an 88 suburban and ended up with the 86 GMC suburban I have now. The motor has been swapped out for 350 Monte Carlo engine from 1977.

 

[nvrenuf]

I believe the '86 truck will still have an electric gauge.

 

[Challis350]

Gauges on these are unreliable. My '85 either shows perfect oil pressure or reads zero. it changes mid journey sometimes.

Engine runs great and has done for over a year.

 

[Rickf]

Have you tried using "SEARCH" that is located in the upper right of the page? There are many strings about low to no oil pressure.

 

[JBswth]

Gauges on these are unreliable. My '85 either shows perfect oil pressure or reads zero. it changes mid journey sometimes.

Engine runs great and has done for over a year.

My 81 Square Body used to do that. Sometimes read fine, other times very low, sometimes zero, but it had hydraulic lifters, and they would have collapsed and clattered it oil pressure really was zero. Tried to swap in the mechanical oil gauge of the 73 - 75 trucks, but would have had to use a 73 - 75 wiring harnesses and make that opening for the two harnesses to connect smaller, so never did it.

J.B.

 

[Ricko1966]

Post #2 and 3 are right on no oil pressure you wouldn't have made it home,and you'd have heard the lifters clatter, followed by rods clatter,followed by silence as the mains stuck to the crank or a rod stuck to the crank. Verify your oil pressure as @nvrenuf and test as test the wires as @Bextreme04 if both pass you need a sender, you probably already knew that but, figured I clarify that just in case.

 

[newguy11]

Sending unit is on the back of the motor behind the intake manifold. If you unhook the wire, the gauge should read zero, if you put a wire into the connector(the wiring harness side, not the sender side) and ground that wire to the block, the gauge should then max out. If the gauge doesn't change when unplugging/grounding the wire, then you have a broken wire or a problem in the circuit/gauge.

I bought this when I had a similar issue.

Engine Oil Pressure Test Kit

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[JBswth]

My 81 Square Body used to do that. Sometimes read fine, other times very low, sometimes zero, but it had hydraulic lifters, and they would have collapsed and clattered it oil pressure really was zero. Tried to swap in the mechanical oil gauge of the 73 - 75 trucks, but would have had to use a 73 - 75 wiring harnesses and make that opening for the two harnesses to connect smaller, so never did it.

J.B.

That is something I wished I could do on the 81 I used to have. That electric oil pressure gauge was erratic. Wish I knew how to weld.

James