Morris Minor Owners Club

Ok so I've just fitted the engine and gearbox after having both out of the car in order to rebuild the gearbox and just check the engine over and clean her up and paint her in the best livery around . Nothing was really done to the engine apart from replacing bits and bobs externally so very little disturbance took place apart from replacing the sump and cleaning up the ancillaries and painting, lacquering where needed. When I started her up everything worked as it should but then after a short while the oil pressure light in the speedo started to glow then shine bright. I have an oil pressure gauge fitted and this still showed 50psi irrespective of whether the light glowed, bright, or not. I fiddled around with the switch [it's barely a year old having replaced it last summer when I fitted the pressure gauge and done barely 300 miles since fitting] and it would sometimes go off for a while but then for no rhyme or reason, it would start to glow dimly or shine bright. I've checked the connections and all seems tight. Any ideas before I go and purchase another ?
P.S I have noticed that the oil in the clear pipe feeding the pressure gauge has air pockets in it which as been there since the fitting, but it seems to move back and foe rapidly when the engines running, not noticed this before.

I think the new gauges are a bit dodgy. I've had a few problems that have always been resolved by fitting a new one...then a couple of years later it goes wrong again. Probably carp modern bits from the legendary tin hut in a distant part of Asia?
Probably worth purging the air from the oil pipe first to see if that solves it as a first step though.

My oil gauge seems to have air in the line as well, and I did purge it once but it came back. It dosent cause any issues with the warning light so probably a dodgy switch as suggested.

Air in the line is not an issue as the air and oil pressure will be the same.

As above I suspect the switch.

Replace the old Minor switch with a high pressure switch.

https://www.minisport.com/uprated-oil-p ... 59-96.html

I agree with Phil. The standard switch will tell you when the pressure has become low enough to kill the engine whilst that 20psi one will tell you when it is startting to be a problem, thus allowing you to fix the oil situation prior to it knackering something.

but it seems to move back and foe rapidly when the engines running, not noticed this before.

That alone appears to indicate the pressure is changing. There is likely a restrictor on the gauge to prevent rapid needle fluctuations which would wear it out prematurely. I would suspect the oil pump - maybe the switch is picking up the low and highs resulting in the 'glowing' but not full on indication. Switches are cheap, compared with an unnecessary engine rebuild and they do fail - so changing it is the best place to start. But do also check for chafing on the wires back to the indication - there could be a short developing.

Does the pressure gauge indication rise and fall slowly at start up and switch off? Does the oil pressure warning light come on before the guage has fallen to close to zero at switch off? Hope it is not a problem more than the switch, but if the air bubbles in the pipe are moving a considerable amount while running at any more than tickover, I might be worried! Alternatively it could be the pressure relief valve opening and returning oil to the sump. Needs checking out for sure.

RAB


Plain bearings need about 5psi oil pressure to keep them apart, so both pressure switches might be favourite for a worn engine at tick over.

Thanks for the replies guys,

The pressure gauge seems unaltered by the light or the rapid movement of the oil in the pipe and it sometimes stays off for a few miles before either glowing or shinning bright so I'm hoping it's just the switch as the gauge needle stays static on tick over at 45lbs and rises to 60 lbs when the engine revs .

Have you checked the earthing on the dash dials? You might have an irregular earth somewhere in the system

Ah I hadn't thought of that .I've just bought a new switch so if it still plays up and the oil pressure gauge still shows good pressure then I'll check out the earthing.

The oil light in the dash, and the ignition light don't rely on an earth in the dash, they have two wires going to the bulb holders. The oil light is earthed via the switch, so the switch is closed with no pressure completing the circuit, opening when there is pressure and outting the light out.

Ah right well that saves me a bit of time then. ....update , I took her for a bit of a drive this afternoon and all went well on start up and 20 miles later so initially my thought's were hooray problem sorted until I parked her up and 20 minutes later switched the ignition on and the oil light just flickered but hey ho I've least I've got good oil pressure showing on the oil pressure gauge and a new oil pressure switch to fit when I get time.

The oil pressure gauge is the way to go anyway, tells you way more than the light does. In general the standard oil light is almost a light of doom for the engine, if that pops on when going along it really means rebuild required.

You've had the engine out...you haven't connected the dynamo wire to the oil pressure switch and vice-versa?

John

I've got an alternator so not sure if that makes a difference but it worked fine on Saturday on a spin out but just flickered when I switched the ignition on some time later and then went out completely but hey ho I've got a new switch so I'll get that linked up and see how it goes from there ....at least it's not my oil pump on it's way out ..... thank god I fitted a pressure gauge last summer.