Engine cuts out on sudden stops

Whitewater · May 30, 2023

Hi folks,
Here’s a question I have been meaning to ask for 15 yrs - my 1.6 single port LHD early bus (1969) has always cut out on sudden rather than gradual stopping. If I dab the accelerator pedal just before such a stop the engine usually stays running.
Anybody out there experienced a similar quirk, even if not for 15 yrs?

Clem · May 30, 2023

Always or just when warming up?

Whitewater · Jun 1, 2023

Hi Clem
Always - I can start her and drive 100 yds to end of my street and it does it or 50 miles up the M5 and it will cut out on the slip road when I brake to stop
Any ideas?

milfredo · Jun 2, 2023

I had this issue and the major problem was with a warn out old carb and the idle jet. New carb improved things for a while but then the problem came back and it turned out I had an air leak from my manifold rubber gaskets. They looked ok-ish (minor cracks) but upon removal, we're swimming in fuel and rotten. I'll dig out my troubleshooting page on here.

ozziedog · Jun 2, 2023

Are we talking about , hit the brakes hard and immediately it cuts out or after a second or two? What sort of carbs etc.

Ozziedog,,,,,,,,,,just fishing for ideas

Whitewater · Jun 2, 2023

milfredo said:
I had this issue and the major problem was with a warn out old carb and the idle jet. New carb improved things for a while but then the problem came back and it turned out I had an air leak from my manifold rubber gaskets. They looked ok-ish (minor cracks) but upon removal, we're swimming in fuel and rotten. I'll dig out my troubleshooting page on here.

Thanks Milfredo,
Will get that looked into
Whitewater

Whitewater · Jun 2, 2023

ozziedog said:
Are we talking about , hit the brakes hard and immediately it cuts out or after a second or two? What sort of carbs etc.

Ozziedog,,,,,,,,,,just fishing for ideas

Hi Ozziedog
it cuts it out immediately if I hit the brakes hard ( a rare occurence, thankfully) but after a couple of seconds at many more gradual stops ( if I am quick enough and dab the accelerator in those couple of seconds it does not cut out).
From memory (the bus is not with me just now but up country for some'cosmetic' work) its a standard carb, not the original and possibly even made in Brazil?
Cheers
Whitewater

ozziedog · Jun 2, 2023

Does sound like a blocked idle jet but I think there’s more to it for some reason. Something moving about somewhere possibly blocking the air filter or shorting out around the coil / dizzy praps.

Ozziedog,,,,,,,,, Hhhhmmmmm

Moseley · Jun 3, 2023

Does you bus have a brake servo fitted?

NigelDenham · Jun 4, 2023

Vacuum leak Somewhere?

sparkywig · Jun 4, 2023

Usually an inlet manifold leak causes the engine to cut out when slowing down.

fatgaz · Jun 5, 2023

Had the same issue, serviced the carbs and cured it. Thankfully.

Whitewater · Jun 8, 2023

Moseley said:
Does you bus have a brake servo fitted?

No Mosely, it doesn’t
Whitewater

Whitewater · Jun 8, 2023

NigelDenham said:
Vacuum leak Somewhere?

Thanks for that Nigel

Whitewater · Jun 8, 2023

fatgaz said:
Had the same issue, serviced the carbs and cured it. Thankfully.

Thanks Fatgaz

NigelDenham · Jun 18, 2023

Whitewater said:
Thanks for that Nigel

Did you sort it?

Whitewater · Sep 24, 2023

Dear all who advised on my 1969 LHD 1.6 bus ‘sudden stop’ engine cut out problem.
I had the carb stripped down but the spindle was too worn so I got a new carb fitted ( photos attached - anyone know what make it is - I think from VW Heritage) and problem solved. There was also an air leak on manifold rubbers as Milfredo suggested.
Backfiring problem also cured much to the relief of the elderly citizenry around here.
Thanks again to Ozziedog and co for all the advice,
Whitewater

70-CA-Panel · Sep 24, 2023

Thanks for getting back with your cure as this can help others.
Glad you got it sorted.
All the best.

ozziedog · Sep 25, 2023

That was actually quite quick when you think it took you fifteen years to ask the question

Well done anyhow and I bet that makes it a bit more pleasing to drive.

Ozziedog,,,,,,,,, great result

Ka1dza · Aug 16, 2024

Whitewater said:
Thanks Milfredo,
Will get that looked into
Whitewater

Did you find the problem? I’m having the same problem but the gaskets we just changed. I’ve changed the coil, I’ve switched the distributor from vacuum advance to mechanical advance. I’ve reset the timing and changed the carburetor! I’ve also changed the fuel filter and all of the fuel lines. All of the vacuum lines and vacuum assist unit has also been changed!!This problem has been going for years!
I get everything setup nicely, the bus runs great for a couple of weeks, then the symptoms slowly come back to the starting point.
Would there be something BEFORE the carburetor?

Engine cuts out on sudden stops

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