Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing 68 Plus Four idles poorly when hot

A friend has a 68 Plus 4 and he says it idles poorly and sometimes stalls when the engine is warmed up. He says that the temperature gauge reads normal when this happens. The engine has a pair of SU H6 carbs. I've got a little experience with the SU carbs on my 52MG TD. Does anyone have any suggestions about where to start?

Thanks in advance,

Gareth Parfitt

Hi Gareth. It might be really useful if your friend joined this forum. Can’t help him myself unfortunately.

You could take a look where the fuel line runs..... the fuel line can get too hot and the fuel will slightly evaporate ... a fix (bodge) would be to wrap the line in bacon foil and see if that makes any difference. If it does, then a better solution will be possible.

it might be worth checking/changing the condenser (capacitor) these often fail when the engine gets hot.

David Byrne

On a Morgan of that age there are so many possibilities, though when hot if the choke is pulled out a little and slowly listening to the revs to detect if there is any improvement. if there is then perhaps the mixture may be too weak which then could be down to air leakage at the manifold or carbs.. ?

Good luck, do come back and let us know what you have tried and the results if any obtained..

Carbs need to be balanced etc...also I found a gunsons colourtune is ideal to check the mixture is right

Our 1956 plus 4 TR engine purrs ...

pm me and ill give you my phone number for your friend...will try to assist.

There are only a couple of things to check. Before starting diagnostics, make sure that basic routine tune up has been done.

Check the ignition system. Your problem is most likely the coil or the condenser. Unless they're new I would probably just replace both.