Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing No oil pressure - help required

Good afternoon, fired up the +8 for the first time in a few months today. Did the usual oil level and coolant checks all ok. Started almost immediately, allowed it to run for a few minutes to warm up but noticed the oil pressure was just above the zero rather than the 2+bar it usually is during warm up. Could possibly be the gauge, looked behind the dash and nothing seems out of place, the gauge does move slightly when I turn on/off the ignition? But want to be 100% sure before I take it for a run is there a way to check oil pressure/flow? Appreciate any advice on possible causes and actions to take - thank you!

Have you just done an oil and filter change since you last fired it up...?

Hi Jeremy,

There have been a number of very different oiling systems and oil pressure sending systems used on Plus 8s over the years and very different Plus 8s for that matter. Could you give us a year?

You are wise not to go for a drive or run the engine just yet.

Lorne

No, oil & filter change was last summer and was working fine after it was done. Everything was good when put away in October. I usually run the engine every couple of months even if off the road, but this time is almost 4 months since the engine ran.

The car is a 1990 +8, supplied in June of that year with the 3.9 engine, I believe it was one of the first with the 3.9 engine.

From a simple google search here are the possible causes on a river V8, if not the gauge, with my thoughts in CAPS....

Common Causes
Air Lock/Lost Prime: The pump cannot pull oil because of air in the system. WAS FINE AFTER OIL CHANGE SO NO AIR COULD GET IN

Stuck Pressure Relief Valve: The plunger sticks in the open position, bypassing all pressure. POSSIBILITY

Worn Oil Pump: Scored or worn oil pump gears on the front cover, which is common in higher-mileage or older engines. UNLIKLEY ENGINE ONLY DONE 10K MILES

Blocked/Damaged Pickup: The oil pick-up screen in the sump may be blocked or sucking air. UNLIKLEY AS WAS WORKING FINE WHEN PUT AWAY

Incorrect Gasket: Using an incorrect front cover gasket or sealant can cause air leaks, preventing pressure build-up. UNLIKLEY AS NOT CHANGED

Appreciate any other suggestions for advice on next steps

Thanks for the heads up. I have read of the oil pump priming issue on +8`s after an oil change, thus that is why I asked... Best avoided by filling up the oil filter with engine oil prior to fitting, all a bit messy but has always worked on my mid 80`s +8.
I suspect you can discount the oil pressure relief valve sticking opened, unless when you last fired it up from cold, you reved the engine high enough fort the oil pressure to rise enough to lift the relief valve off it`s seating and it stuck opened.... which I suspect to be very unlikely..?

The screen in the pickup would only likely to be restricted if there was a high degree of crud in the oil, which seems very unlikely given your description of mileage/usage
Hard to imagine gasket issues.
All of which seems to be pointing towards sender or gauge issues.... Any chance of rodent attack on the wiring...?

Sorry not up to speed with the type of instrument fitted to later +8`s, there may be a simple way to check that there is oil pressure..? I suspect that with a 90`s +8 there might be a fuel pump cut out that depends upon oil pressure to allow the fuel pump to switch on.... Thus if the fuel pump was running long enough for you to discover the lack of oil pressure...? On the other hand perhaps the EFI system uses air flow sensing to allow the fuel pump to run...Does your dash have an oil pressure warning light...?

There are others better informed than I who will no doubt jump in when they read of your plight...

Thanks, appreciate the thoughts. Agree with your thinking on the pressure relief valve. The dash warning lights do not have an oil pressure light sadly. It ran for 3-4 minutes before i realised that the oil pressure was low, the engine sounded ok but increasing revs did not increase the pressure on the gauge as it normally would so turned off. Will restart engine tomorrow and see if i can detect any other signs to help with the diagnosis.

Won't that motor have hydraulic tappets? ...surely they'd be clattering like a flamenco dancer if there was no oil pressure.

K

Most likely an electric pressure gauge, could be an issue with the sender, the cable, or the gauge. or lack of power to the instruments, does the fuel gauge work ?