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

Fuel gauge works, as does the battery voltage and the water temp.
Looked at wiring behind the dash, all leads seem connected, I'm sure its an electric pressure gauge as no oil feed pipe, so will look at the wiring for the cable/sender unit. Thanks for the advice.

I don't know? Does the 3.9 V8 have hydraulic tappets? Will check. Thx

Checked, it does have hydraulic tappets, so did it not have massive tappet noise, so looking like gauge issue of some sort. Thx

Dependant on which type of gauge is fitted, if you switch the ign on, then pull the connection off the sender unit, the needle may read max pressure. I am guessing the sender may be located at the location of the oil pump/filter alloy casing the wire colour might be light green with a red tracer. check the connection for damage or crud that might be acting as a resistance.. I left my hat in the glove cubby hole and a mouse chewed lumps out of it, how it got in there, I have no idea must have been a gymnast, so not about to give up on rodent damage to the wiring yet... Do you have a volt/ohmmeter and can you use it..?

The clatter of hydraulic tablets with less than full oil in them is very noticeable when their oil cavities are empty following rebuild. However in this case despite not being run for four months it's reasonable to assume they contained oil which would take a while to leak down before any great noise was heard.

Having mentioned this I would strongly suspect a faulty gauge system with a possibility of a high resistance connection somewhere given the lay up.

My 2002 Plus 8 had a separate oil pressure sender just for the gauge. I had to replace it as the gauge became erratic. It's a pressure switch wired to the gauge, screws into the engine block rear. Two wires onto spade connectors. Easy to replace. Bought replacement from Melvyn Rutter, not expensive ( for a Morgan). A quick change whilst underneath and car on stands. Access good.
Seeing the gauge become erratic was not pleasant! The ecu would stop the engine if no oil pressure based on a sensor elsewhere ( oil pump I think from memory). Oil pressure on a Rover V8 was not high anyway. Seeing the gauge drop at idle speed was normal but took some getting used to!

Thank you for the extra info, Jeremy.1990 was quite a transition year for the Factory! I know 5 of us of now. For more than a decade, I kept a 1990 Plus 8 I had restored in the UK. It apparently left they Works a few of weeks earlier than yours (R10326) so it had 3.5 which I swapped out for Lorne-tuned 4.6.

To reduce well-intentioned confusion, all Morgan 3.5s and 3.9s unlike.LR who used them until the GEMS variant (with a transition front cover period). I even use them on my 4.6s. At some point in the early/mid 1990s, the company wisely switched to an electrical rather than mechanical oil pressure gauge signal. Land Rover merely had a dash idiot light which usually meant the engine was toast before a driver could react to it.

I like these pumps, as they are eminently repairable at home by amateurs who can also upgrade them. But the mechanical hose system is inherently dangerous [i]as my Help inbox indicates for the last 30 years [i]. BTW, the swap from mechanical to electric is discrete and easy, whether you have VDO or for those with Smiths gauge. I do that with all my Plus 8s. If we know which sender system you have, it will eliminate a lot of bandwidth. You can confirm by looking behind the dash at the oil pressure gauge. Is there little yellowish hose going into the rear of the oil pressure gauge? Checking your era's Plus 8 at the oil pump is unhelpful as the MMC kept using the one-shot oiler (shiver) for MANY years after they stopped using mechanical oil pressure gauges. Our Morgans are very simple, you just have to be contortionist. (wryly) This additional info will save much bandwidth.

Once we confirm the cause of the unacceptably low reading gauge, a fix should be simple.Luddite's question wisely points to the most common cause of your observations..namely a loss of pump prime (a notoriously common problem with them), There are methods used re-create the prime. And, BTW, there is a special sequence to use when changing oil on a LR/Rover Plus 8 with these pumps.

Lorne

I found a little time yesterday to continue the diagnosis, see enclosed pictures of the back of the oil pressure gauge, no yellow hose, which confirms its a electrical gauge. I could see a 'take off' from the oil filter housing, see picture, but could not find a sender unit. I need to get under the car but don't have my jack / axle stands with me at the moment......

Having trouble posting pictures.....to big.....

But then did start the car again to confirm no tappet noise.....started ok, smooth no excessive noise, but after a couple of minutes it got noisy! So turned off.
Have a video but don't imagine that will post either!

Next step, re-prime pump? Or what?
Appreciate any input.

Thanks for the help and support.

You need to open a third party picture hosting account Jeremy. Suggest imgbb or tm_img, both are free. Either will allow you to upload your image(s) with generally no size limitation, then provide an image link you can paste into your post for direct display.