Morris Minor Owners Club

Hi,

I've got a 55' series II morris and it starts without issue and generally runs fine, however when caught in traffic it starts to run rough and eventually cuts out. When left for 1/2 an hour it starts running fine again as if nothing was wrong. Unfortunately stuck in traffic on the A406 is the last place you want to break down! and 1/2 and hour is quicker than the AA seem to respond.

The engine doesn't see to get that hot (certainly I can't tell the difference between getting home after a normal run and just after its cut out). There's no humming from boiling water or smell of a burning engine. I can even touch the dipstick which would suggest to me that its not THAT running hot.

This cutting out happens in about 5-10 mins of heavy traffic.

I was thinking maybe the fuel is vapourising because of the lack of flowing air? Maybe the fuel line runs too close to the exhaust manifold? If so how would I gaurd against this? An electric fan like on modern cars will only keep the coolant cool, would it not?

Any advice/help would greatly appreciated

Richard

If not over heating, it might be fuel vapor lock. You could try fitting a heatshield between carb and manifold. I would also check engine breathing (PCV) is clear with no leaks in the hose. Also fuel level in float chamber, just incase it's too high, which doesn't really effect travel at speed, but can flood engine at idle.

Thanks for the info. My reasoning behind the vapour lock is that it doesn't seem to be an issue in winter (if I remember correctly it hasn't happened in the cold) or if I get stuck in a jam outside my front door (i.e. with a cold engine).

I'll certainly try what you've suggested. Thanks again

If the fuel pump is going nineteen to the dozen when this happens - then yes it is fuel vapourisation. Only certain cure is to relocate the pump low down in the engine bay - so it has almost flooded suction from the tank. It can easily pump fuel up to the carb - but it's not good at sucking fuel with vapour bubbles upwards from the tank. you can try wrapping pipe with tape etc - but lower pump is the answer. If the pump is not running - it may of course be sticking - give it a thump, or - the problem may be overheating condenser (capacitor) inside the dizzy. Just to check -try fixing a radio suppressor on the outside of the dizzy - cable to input wire and body to earth - and see if that eliminates the problem!

Also a symptom of a failing ignition coil I seem to remember

Thanks for all replies, the fuel pump going mad rings a bell!

I'll try moving the fuel pump but I guess the real solution would be to stop it getting so hot under the bonnet in the first place?

Difficult in hot weather - it's the modern unleaded fuel that seems to cause the problem - wasn't so much of a problem in the 'old' days!

Our 65 convertible has had the same problem, the SU fuel pump (new 18 months ago) points were very pitted. Cleaned them up and prob's gone. I too thought this was fuel vapourisation but none of the pipes are within 6 inches of exhaust so an unlikely cause.

I wouldn't think that being hot under the bonnet would be a problem. I drive a totally unmodified 55 2 door (admittedly it does have a the 'newer' 948cc motor) around the Top End of Australia where the temperature very rarely drops below 24c...at night! Although it did get down to 19c the other night, I had to put a shirt on. But I digress...the A series motor is very well cooled. I have never overheated any of my Moggies here. I reckon having a look at your fuel pump as stated above might be the go.
You've made my day BMC, a bloke from Central Scotland talking about hot weather! I think if I was there in summer you'd spot me a mile away, I'd be the bloke in the parka with hot water bottles stuffed down my trousers.

Thanks ferret - we just 'love' our cool/wet weather in Ecosseland!! Actually - it's been quite warm and humid last few days - getting fed up with it!! Nice downpour promised for this afternoon though.