Car shuts off on when braking

[Smithgall]

I have a new development. My car has started shutting off when I brake hard. Not exceptionally hard. But anything over a slow coast to a stop will cause this. I can sometimes off set this but dropping into a lower gear but if I just hit the brakes it will shut off. This is a new development and im not sure what it may be. 

Battery is not loose. tank is full. and it starts immediately when this happens. 

Any ideas? 

[Dave B.]

Mike,
Some years ago a friend asked me to look at her Plymouth Duster because every time she turned left (or right–I can’t remember any more) it would stall.  It never stalled when she turned in the opposite direction.  I didn’t believe her until I test drove it myself.  I had a mutual friend with much more automotive experience, and I told him about it, and he didn’t believe it either until he drove it.  It turned out to be the carb float, which hinged on one side and was cutting off the fuel when centrifugal force took it in the wrong direction.  The solution was to rebuild the carb.  So there’s one possibility, if that’s consistent with your carb arrangement. (It’s been so long since I’ve worked on an air-cooled VW that I don’t know whether the symptom could be consistent with the VW setup, but I’m sure the VW gurus will weigh in on this point.)  Another possibility would be an ignition wire or other ignition component that might be shorting to ground when you brake.

[Dave B.]

In this thread:

http://www.thesamba.com/vw/forum/viewtopic.php?t=62172

the writer says his idle mixture was too lean.

[Royal]

I believe that the float would have to be WAY off to experience this. More likely, assuming it is not an intermittent electrical prob is that the carb mixture is too lean, and when you take your foot off the accelerator pedal to apply the brake, the throttle butterfly goes shut and starves the engine. Back off on the mixture screw a bit (see Rob and Dave’s VW resource for guidance). Increasing idle speed may also help. I think that VW recommends 850 rpm (check the number – i’m old). I prefer an idle speed more like 1000-1050.

[edward ericson]

VW says 900.

Make sure there’s noting fouling it in the air cleaner, choke butterfly is right. 

Look for the wire that attaches to the carb–there’s a kill valve on the later Solexes to stop run-on. Could be a loose connection there. Check all the connections. Make sure the distributer is in tight. Rock the engine front to back to be sure the mounts are right and nothing is binding, especially on the throttle cable.

If nothing gives, and nothing fixes, then do a tune up. Sparks first and timing and then adjust the carb per the Muir procedure.

[Smithgall]

Thanks guys. i did check the connections and they all seemed to be fine. I then turned up the idle a bit and that seems to have worked. I did a test drive around the neighborhood and tried to stall it with some hard stops and no problems. Hoping that is all there is. Im not really a mechanic beyond the normal knowledge that men seem to possess as part of our dna but i enjoy working on the vw. Its so simple. Its all right there. easy to get to. Thanks again for your help. 

[Royal]

You may, by turning up idle speed, be masking a vacuum leak. While idling, you can squirt engine oil around the throttle shafts and intake manifold at the base of the carb and where the manifold mates up to the heads. Squirt, and listen carefully for changes. Don’t hurry. Any change indicates a vacuum leak. The engine may not respond immediately. Patience and concentration. I sometimes use a stethoscope other times, a piece of aquarium hose crammed into my ear. Keep a close eye on the tach. ….all this is to be done with engine fully warm, and choke off.
What is idle rpm now?

[Paul Mossberg]

Mike,

 

Here’s a similar discussion on the allaircooled forum. The two most likely causes are vacuum leaks as discussed in this thread or the electric idle shut off on the stock carb.

 

http://allaircooled.websitetoolbox.com/post/stalls-when-braking-3078654?trail=15

Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster

If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)

[Royal]

Geez! I forgot about the idle shutoff. I had a problem with mine a few years ago and defeated it by cutting off the little plunger. ……it ain’t no fun etc etc[EMAIL= ][/EMAIL]

[Author]

Posts