Cutting out on deacceleration

[Greenstag]

Hi Folks

This is really beginning to niggle me because I think I've fixed it and then it comes back again.

If I go for a good run which includes a dual carriageway or motorway section ie 60mph plus, as I lift my foot off the gas for a roundabout etc the revs drop to zero and the engine cuts.

An on the move "bump start" gets her going again immmediately and then its a case of gently down the gears or blipping the throttle to keep the revs up. Town driving is fine.

My first thought was dashpots but these are nicely topped up. (should I check the piston movement in there?) I replaced fuel and air filters, and plugs and given the carbs a good dose of cleaner. No apparent air leaks in breather system. It just like it doesn't like rapid power decrease.


As always, any pearls of wisdom from the carb experts greatly appreciated ...I'm assuming it's carbs...original Strombergs by the way

Regards

Dave

[stag157.7]

Hi Folks

This is really beginning to niggle me because I think I've fixed it and then it comes back again.

If I go for a good run which includes a dual carriageway or motorway section ie 60mph plus, as I lift my foot off the gas for a roundabout etc the revs drop to zero and the engine cuts.

An on the move "bump start" gets her going again immmediately and then its a case of gently down the gears or blipping the throttle to keep the revs up. Town driving is fine.

My first thought was dashpots but these are nicely topped up. (should I check the piston movement in there?) I replaced fuel and air filters, and plugs and given the carbs a good dose of cleaner. No apparent air leaks in breather system. It just like it doesn't like rapid power decrease.


As always, any pearls of wisdom from the carb experts greatly appreciated ...I'm assuming it's carbs...original Strombergs by the way

Regards

Dave

sounds like its running weak on the overrun
any popping back through the exhaust?

carb dashpots drop nice and easy?
only a few suggestions
alan

does it tickover at idle ok?

[john 4d]

That's also another symptom I'm experiencing, it been suggested that the vacuum diaphragm on the distributor is not functioning, perhaps perforated or perished. Could this be true?
John4D
p.s.
popping back through the exhaust? Yes
sounds like its running weak on the overrun? Don't know what that sounds like!

[Greenstag]

Thanks Alan, thanks John

No popping on the over run and normally ticks over quite nicely. I'll get the dashpots out tonight and check movement.

The vacuum advance is something I haven't checked recently ..

Regards

Dave

[martin]

Hi Folks

This is really beginning to niggle me because I think I've fixed it and then it comes back again.

If I go for a good run which includes a dual carriageway or motorway section ie 60mph plus, as I lift my foot off the gas for a roundabout etc the revs drop to zero and the engine cuts.

An on the move "bump start" gets her going again immmediately and then its a case of gently down the gears or blipping the throttle to keep the revs up. Town driving is fine.

My first thought was dashpots but these are nicely topped up. (should I check the piston movement in there?) I replaced fuel and air filters, and plugs and given the carbs a good dose of cleaner. No apparent air leaks in breather system. It just like it doesn't like rapid power decrease.


As always, any pearls of wisdom from the carb experts greatly appreciated ...I'm assuming it's carbs...original Strombergs by the way

Regards

Dave

To be fair to these old girls, there's something of an obsession on here with low emissions, I know it's the MOT, can't blame anyone for worrying, but this is one of the side effects, I think 157 is right, she's running too lean.
I'm lucky, mine's a '74 so only concerned with smoke, but with other old cars, our local guy will drop the mix for the test then put it back where it belongs straight away. People who quote figures of less than 1 are doing themselves no favours. Try enriching the mix a quarter turn at a time, it should give up that 'orrible habit. Martin.
P.S. have a look for very small holes in the diaphragms.

[Gresley]

Hi Dave,

I had exactly your symptoms when I first had my Stag, it turned out to be one of the air valves in the carbs sticking. I think it had got some grit into the dashpot at some point.

Brian

[Greenstag]

Hi Brian

Thanks that's another good lead and something else I'll investigate at the weekend

Cheers

Dave