1936 accelerator starter switch rebuild

[JoelsBuicks]

I’ve been unable to find a rebuilding service for the ‘36 accelerator starting switch.  The switch itself is robust but the vacuum diaphragm is deteriorated.  Apparently, Bob’s has tried to get these rebuilt by the folks that rebuild distributor advance control units but with no luck.

 

I have disassembled one of these switches to reveal the failed diaphragm.  If I had the right diaphragm material, I’m pretty sure I could get this back in working order.  Has anyone done this?  Any suggestions on material?  Interestingly, it is the same diameter of the vac advance unit.

 

Thank You,

Joel
 

 

[Buick35]

I've got one for my 35 Buick that also could use a rebuild.It looks fairly similar to yours. Let me know what you find. I mounted a push button for my starter.Thanks,Greg.

[JoelsBuicks]

Greg, I’m trying to find out who does the vac advance work for Bob’s so that I can talk with them about providing, at a minimum, a diaphragm. Better yet, provide a diaphragm that is mounted to the old actuator stem that we’d provide.  I’m still asking Bob’s for help with this and hope that they’ll at least pose this question to their rebuilder.   I’ll report back.

 

 

[Buick35]

Thanks,I'm sure this has to be a common problem for our old Buicks.

[groselle]

Have you look at a lawn sprinkler valve.  They use a similar diaphragm setup, so maybe you could scavenge the material from one.  Another option is McMaster-Karr (https://www.mcmaster.com/). I've had great luck finding raw materials from them.

[JoelsBuicks]

I looked at the lawn sprinkler valves and those diaphragms look to be thick and molded.  The diaphragm material I need is about 0.015” thick or about 1/64”.  McMaster has some 1/32” polyester reinforced neoprene and that looks very interesting.  I found some 1/64 neoprene on eBay but it doesn’t have any reinforcement.  I might just buy the stuff from McMaster.
 

Thanks for the suggestions. I’d still like to hear back from Bob’s.

[Bloo]

It will need to be resistant to gasoline for sure, and now ethanol too. Choose carefully. I have seen a 37 Buick fuel pump diaphragm that was made of several layers of doped cloth. The modern gas washed the doping right out, and it leaked like crazy through the cloth. It is not unreasonable to think that if the original material was used today in your switch, the vapors might attack and damage it. Maybe something made with flourolastomer might be appropriate?

 

EDIT: Some common materials did not do so well with 10% ethanol.

https://www.hindawi.com/journals/jfu/2014/429608/

 

Edited May 28, 2020 by Bloo (see edit history)

[JoelsBuicks]

58 minutes ago, Bloo said:

It will need to be resistant to gasoline for sure, and now ethanol too. Choose carefully. I have seen a 37 Buick fuel pump diaphragm that was made of several layers of doped cloth. The modern gas washed the doping right out, and it leaked like crazy through the cloth. It is not unreasonable to think that if the original material was used today in your switch, the vapors might attack and damage it. Maybe something made with flourolastomer might be appropriate?

 

EDIT: Some common materials did not do so well with 10% ethanol.

https://www.hindawi.com/journals/jfu/2014/429608/

 

Well that’s an interesting study and for sure neoprene is out. The Delrin is promising and your suggestion of a fluoroelastomer deserves some research. I don’t want to have to open this thing up and fix it again!

 

Thanks

[Robert Engle]

I have a diaphragm out of a 32 50 series Buick fuel pump that looks like it might work.  Material is .036" thick on an old unit.

 

Bob's sells rebuild kits for the 32 Buick fuel pumps.

 

Bob Engle

 

 

[JoelsBuicks]

Bob, that would probably work.  A new kit would cost $69 just to get that diaphragm.  I may try a Nylon reinforced nitrile That I found on eBay.  It’s less than $20 shipped.

 

i read about a guy who used an inner tube and it worked.  I’m pretty sure that wouldn’t work for long.

[mcdarrunt]

I have made a vacuum start switch for use with a 1952 263 engine with a Stromberg carb. The prototype is big and ugly and does not mount on the carb but uses a vacuum line to a remote mounting. Right now the body is pvc tubing and the piston is teflon rod. Getting the return spring to match up with the Orings on the piston was the tough part. It DOES work but not close to being a finished product. The finished product will need to be much smaller, have a brass, aluminum, or stainless body, have an insulating material for the contacts in the piston and the bottom of the tube. I searched for a normally closed vacuum switch that worked in a cars vacuum range and had no luck but if there is one out there it would be the way to go.

[michealbernal]

You might consider contacting Special Interest Autos in Texas at 800 634 2469.  They advertise in Hemmings Motor News that they rebuild vacuum advance units.  I have had them rebuild vacuum advances in the past and they did good work for me at reasonable prices.  Possible they could assist youl

[pont35cpe]

They(Special Interest) made up speedometer cable/housing for me. Quite satisfied.

[JoelsBuicks]

To follow up on this, I took Bob Engle’s suggestion and I cut a new diaphragm from a recent fuel pump diaphragm.  It turned out that the old material was in great condition because it was protected via multiple layers.

 

I wish I had taken more pics but the end result turned out very well.  It sealed up and actuates the switch like intended.  How long will it last?  We’ll see.

 

Thanks,

Joel

 

[Buick35]

Hi,I thought I'd try to replace the bad diaphragm on my 35s vacuum switch. I forgot that I had an old junk Holley carb.sitting around so I thought I'd try and use the vacuum diaphragm out of it and it fits really close. I just need to know what size is the orifice on the bottom of the switch supposed to be? I might have lost the old adapter that goes into the manifold.Thanks,I'll let you know if it works.Greg.

[Buick35]

I found one on e-bay for my 35.n.o.s. for $85. He said he has one more.Vintage Auto parts in Geogia.Nice guy to deal with. I tried rebuilding mine but no luck.Greg

[JoelsBuicks]

On 6/13/2020 at 5:32 PM, Buick35 said:

Hi,I thought I'd try to replace the bad diaphragm on my 35s vacuum switch. I forgot that I had an old junk Holley carb.sitting around so I thought I'd try and use the vacuum diaphragm out of it and it fits really close. I just need to know what size is the orifice on the bottom of the switch supposed to be? I might have lost the old adapter that goes into the manifold.Thanks,I'll let you know if it works.Greg.

That orifice is 3/64” diameter - as measured using a drill bit.

[Buick35]

Thanks.