Morris Minor Owners Club

The various lights on the speedo - red ignition / blue high beam - so i'm assuming the yellow right hand one is the oil light? (My manual has the dashboard for an earlier model it seems!) In which case, why does it come on when i am in traffic and the turnover plummets towards dying? Oil is all good (if i can't do anything else, i am an eagle eyed one for the basic pre-flight checks!)

any thoughts greatly appreciated - i will also add a question about top end acceleration in a minute on the mechanical bit....

The light is the oil pressure switch which may come on when idling but go out when the revs pick up. The switch is designed to come on about 5psi. Obviously, if the car was only generating 5psi of oil pressure, the engine would be toast. Most folks choose to do one of two things. Replace the oil switch with a new one - which is OK but still leaves you wondering what is really going on inside the block, or, fit an oil pressure gauge using the hole the switch goes into if using an electric sensor or go for the capilary feed option. There are plenty of threads about the oil gauge on the forum if you type that into search. With the oil gauge, you can tell what is going on at all speeds and conditions and is often an early warning that the engine is nearing a rebuild.

Good luck

If you're worried that the lights behind the dash could have got mixed up at some point, both the oil pressure light and the ignition light should be on when the ignition is switched on, but the engine isn't started. To tell which is which, pop the bonnet and pull the wire off the oil pressure switch. Go back and switch the ignition on and see which light comes on.

Both should go out shortly after firing the engine. the ignition light can come on when stationary if your tickover is set very low. if the oil pressure light is coming on, as brucek says, your engine would be mullered. So it's likely to be the switch!

A worn /hot engine on slow idle may well show the 'low oil pressure warning' light. But as above - check in case the bulb holders have been mixed up at some time. An oil pressure gauge is a v useful accessory - well worthwhile. But as long as the 'oil' light goes out as soon as you lift the revs - the engine will be good for many a mile yet!

You say the tickover is slow to dying... this is a simple fix and would naturally cause the oil lamp to come on, as well as the ign lamp. Simply adjust the throttle stop screw to increase the idling speed (only adjust once the engine is thoroughly warmed up).

The ign lamp will come on at idle because the engine speed may not be high enough for the dynamo to cut in and charge the battery - this is nothing to worry about and says so in the manual.

How many genuine miles has the engine done?

As for replacing the oil pressure switch and relief valve, hell I should know that's not much good when the big ends are going on the A1 South.

The same thing happened to my minor when on a club run on easter monday. After a 15 mile journey at 50mph, when pulling in to the car park / idling the oil light flickered. The idle speed was a bit low (ign light lightly flickering also). I raised the idle speed slightly. Then done another 15 miles at 50 mph and checked it again, oil light hasn't came on since
I will keep an eye on it and replace the switch if the light flickers again at idle.

Nothing wrong with the switch - it's doing exactly as it designed to do -warning you of low oil pressure! An oil pressure gauge would be a good idea.....

is there any oil coming from the switch i had a switch with the diaphragm pinholed and once the oil was warm and thin the light would flicker due to the differential pressure in the switch equalising, cured it with new switch

There is the alternative 22psi oil switch, at least you get a bit more warning, but as bmc says the actual gauge can tell you a lot more.