[T2] Engine intermittently turns off while coming to a stop

[Andy McKinley]

Max,

The US '71 model did not have a brake booster, but here goes anyway.

You will need either a hand vacuum pump, a length of hose and double ended
hose barb that fits the vacuum hose on the bus and your length of hose, a
clean rag, or your local hooker.

You can check the diaphragm by disconnecting the vac hose in the engine
compartment. The hose on later vans comes through the firewall on the port
side (that's the left side looking at the van from the rear for
landlubbers). It's more like a plastic tubing than rubber, and should have
a check valve in it about two feet from the firewall (it's black on one end
and white on the other. If you don't have the check valve, you will loose
your power assist if the engine dies. a surprise you don't
need). Disconnect it wherever is convenient, and visually check for brake
fluid. No? Smell it. If it smells of brake fluid, your master cylinder is
bad, and the diaphragm is either toast or on its way out. Change them
both. If not, use a vacuum pump ((I just clean the hose up and suck on it
(unless I have funds for the hooker) but I cannot reccomend either 'cause
it's all HAZMAT & such)) to evacuate the system. Keep in mind that you have
some air that has to be evacuated before you start seeing (feeling) some
vacuum build up due to the air in the system. Once you see some vacuum,
stop pumping (put your/her tongue over the end of the hose) for a few
seconds. If the vacuum doesn't go away, your booster diaphragm is intact,
and chances of getting your bus pregnant are slim. If air flows freely
through the system, the booster is bad, or there is a hole in the system
(tubing is steel under the length of the van, could have rusted through
somewhere).

I have this cheap plastic piece of, well, plastic:
http://www.mityvac.com/pages/products_bcbe.asp
You'll need some hose and adapters, too. It sucks as a brake bleeder (no
pun intended), but holds a good vacuum for troubleshooting stuff like this.
If you think you might want one of the better models, do a CBA. The hooker
might be a better bargain.

I'd first look for a vacuum leak in the brake booster system. Loss of
vacuum will decrease the air velocity through the carbs, diluting the fuel
supply.

I experienced these same symptoms in my '72,  and using the same method,
correctly diagnosed a bad booster .

Andy

'72 hard top Westy
'79 Kombi

On Tuesday, September 2, 2014, Max Bronsema <max.bronsema at gmail.com> wrote:

> Bob and Joseph,
>
> Thanks for the quick replies. It does not seem to cut out while shifting
> about the gears with the clutch depressed. I do apply the brakes to stop,
> :) so maybe it is the brake booster diaphragm. Is the diaphragm easy to
> check or is it basically put a new one in and see if that fixes the
> problem?
>
> Thank you all,
>
> Max
>
>
> > I assume you are applying the brakes when stopping.
> >
> > I would check the brake booster for a rubber diaphragm leak. When you
> > apply the brakes, if there is a crack in the rubber
> > diaphragm it can open a bit impacting the carburetor  performance causing
> > the engine to stall.
> >
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-- 
Andy McKinley
airhedz at gmail.com

Love your country, but never trust its government.
-- Robert A. Heinlein.