Morris Minor Owners Club

since changing the engine and reusing the same oil pressure switch, its been coming on and off when it pleases, even though the sump is nice and full and holding its drink well.

i have one pressure switch on the actual block and what appears to be another one on the oil filter housing. i swapped the cable from the filter housing to the block, just in case it was the cable, but still the light comes on and stays on, regardless of revs, speed or anything else.

so, could it be the switch or something much more less obvious?

The switch on the filter casing is there to show when the filter is blocked - any light connected to it should NEVER come on - unless the filter blocks - which is a rare and unusual event - only after many many thousands of miles! The normal oil pressure switch - in the block, near the dizzy, lights up when oil pressure is dangerously LOW. If it comes on any time other than when the engine is hot, and idling slowly, you should switch off immediately before damage is done. You really really really NEED an OIL PRESSURE GAUGE. I suggest you move heaven and earth to get one fitted asap. Meantime - if the oil warning light is on - don't run the engine ! Remind me what's been done to this engine - I know it 's got new pistons/rings - but what was done to the crankshaft/bearings/oil pump ? Did you have the oil pressure relief valve out for cleaning/inspection ?

how would the oil pressure be low? its got a shinny new oil pump, all the lovely little oil lines are all clean. nice shinny new oil filter. the light does go out now and then, but comes back on now and then. it sometimes will come on will stay on and then when i use the car later in the day its off and will pop on and off occasionally through out the trip.

hence i am a bit confused.

also, where would one pick up an oil pressure gauge? will a normal garage have one or do i have to reopen the wallet, mortgage the house and walk to work in order to get one?

Strange effects then ! But the MOST important thing is an oil pressure gauge - usually plenty on ebay. You need a T piece if you want gauge AND oil light - but in the short term - sacrifice the light to have just the gauge working.
Something like this is fine - http://cgi.ebay.co.uk/Smiths-oil-pressu ... 2a0578121a although need to ask if it comes with the pipe and fittings - and you can't afford to wait 5 days !! You need a gauge NOW!

ill borrow a guage from my local garage on monday and give it give the pressure a check and purchase one of flebay

Could just be a dodgy oil pressure switch, worth swapping for another (is the one in the oil filter housing the same thread?). Less likely, but possible, is the bulb itself broken, the filament may be making contact intermittently.

ill have a fiddle on monday afternoon,

by the by, what should the pressure be when idling?

Ideally - when hot and idling - should be ~ 25 psi, going up to 60 psi as soon as you lift the revs.

from my own recent oil light problem, swap the oil switch but also check the pressure as bmc suggests.

a crude was to test it without gauge is to unscrew half way or remove the oil switch, unhook the coil and turn the engine 1 or 2 times, if you have lost oil pressure no oil will come out from around/out of the oil switch.

keep us posted!

ahh, now their is a suggestion. ill do that before i have to buy a pressure gauge,

That would tell you if you have NO oil. You NEED a pressure gauge - every Minor should have one!

never had a gauge in many years of running minors, do you think i should get one

Absolutely - can save your engine! BMC thought it was important enough to put one in all but the very basic Minis.

Basically, all the OP switch does is supply a ground for the warning light.
From your description I would suspect that you have an intermittent ground on the wire from the OP switch to the light. Check the wire carefully, especially where it goes through the firewall (bulkhead).

aupickup wrote:never had a gauge in many years of running minors, do you think i should get one

Ignorance is bliss!!! I spend half the time watching the gauge drop. If I did not have a gauge I would not worry about low oil pressure and would have hammered the engine to death

FIXED!!!!!! a shinny new oil pressure switch has indeed cured all.

Lucky you! But I thought it was already a NEW switch ? Please please - get an oil pressure gauge asap!

never had one , do i really really need one

No - don't bother Dennis - just wait for the big ends to rattle and the engine to seize !! It's a small expense - with the potential to save a whole lot of trouble and expense!