Morris Minor Owners Club

hi guys, could someone tell me what causes the engine to run on for a bit after switching it off. is it the carb that's badly adjusted. can't find anything on this forum as there's so much stuff!!
cheers

The most common cause is that the tick over is too fast! try slowing
it somewhat. If that doesn't improve it then you appear to have
something in the engine which is getting hot enough to ignite the
fuel even with the ignition off. This is usually carbon deposits.

The usual cause is that the mixture is too weak.
Try making the mixture richer by unscrewing the adjusting nut at the bottom of the carb.
Do it one flat at a time until the engine stops running on.

I had the same problem on one of our Minors. Swapped carb, distributor, etc and checked all gaskets. Just lived with it for years, then swapped the engine. New engine = same problem ?????. The only common part was the manifold. Swapped that and the problem vanished. Conclusion: pin-hole in the casting which produces the weak mixture mentioned above.

Or just change make of petrol - give it some good stuff and see what happens. Also a good hard 'thrashing' to clean out all the gunge inside the head !

Your Minor is probably still set up for 4-star (98 ron). I ssume you're using the standard 95 ron unleaded? Adjust the idling speed as Willie said (until the ignition light glows dimly) and use super unleaded, or even better, Shell Optimax.

At the moment I use super unleaded / Optimax and Castrol additive (including an Octane booster) so effectively I'm using 99 or 100 ron fuel!. There's no hint of running on and the performance is great (well, by 1098cc minor standards anyway.... )

Try to adjust the timing on the rouletated screw on the dizzy. then the tick over probably will stop.
cheers mate from Denmark

I thought RON98 fuel only had its advantage in high compression cars? With engines that exceed the 10:1 compression ratio? I can't tell, but did we always have ron98/4 star? I did read 1920's cars run the best on ordinary 95 without additives

Onne

I think pre 1920 they did not add Lead to fuel and also the octane rating was much lower which would explain why they don't mind normal unleaded.

Old 4 star was I think originally ron98 and 2star 91ron so when original unleaded came out at 95ron most cars needed adjusting (if their valves were hardened) to use the lower rated fuel, My old Triumph Acclaim loved Unleaded because it was built for 2star and so Unleaded was a step up.

Paulk

No point in using high octane fuel if the compression ratio is standard - but good fuel (Shell/Esso/BP) can make a difference over supermarket stuff. Won't cost much to try it !

Well there IS a point to using it. Lower running temp, more power, less prone to pinking, etc. But it would be a good idea to try good fuels.

No point in using high octane fuel if the compression ratio is standard -

There is a point if the engine is still set up for 4-star and hasn't been retarded. Last year I had to top up my mog with standard unleaded and I instantly regretted it, suffering from rough running, low power, pinking and severe over-run.

Optimax & additive definately makes my standard (8.3 :1) 1098cc engine run more smoothly and pull better - it's particularly noticeable in 4th gear from 40-60mph.

Only need high octane fuel for high compression ratio. Otherwise it's a waste of money.

Cam is very right on the temperature side of things though! I can feel the difference, since my exhaust shield is missing. So it does make a difference.

What should minors run on originally???

Cheap and cheerful 3 star !

what is that in my language? We don't use 2 star 3 star and 4 star. But I expect ron95?

Well, some people used 3 star but a lot used 4 star!

Using an additive (with octane booster) with modern unleaded is much better for the engine for the reasons Chris, Onne and myself have stated. It DOES make a very noticable difference.

But somehow I don't think we can convince everyone....

BMC, surely you would agree that an engine suffering from knocking & pinking is going to be down on power output and not working efficiently? I'm not claiming the 98 Ron fuel makes my minor develop more than 48bhp but it produces smooth running and consistent power delivery. I didn't dream the symptoms of poor running when I briefly used the 95 ron unleaded.

Well mine runs with an leaded head best on the local Sainsburys LRP.