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Carburetors, Mixers, Fuel Pumps and fuel delivery Discussion about misc. carbs, mixers, fuel pumps, injectors.

Carburetors, Mixers, Fuel Pumps and fuel delivery

Rochester Accelerator Pump


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  #1  
Old 11-08-2016, 09:04:25 AM
TomBall TomBall is offline
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Default Rochester Accelerator Pump

I recently rebuilt a Rochester single barrel B model carb on a 1944 GMC truck. The pump I took out was leather and the new one in the kit was leather also. The new one had a band around it for protection. I soaked the new one to help make it swell but it doesn't seem to expand enough to fit the bore snug enough, hence it doesn't pump properly. Is there a rubber style pump around to replace the leather one or does anyone have ideas on the subject to cure the problem?
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Old 11-08-2016, 12:56:15 PM
Power Power is offline
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Default Re: Rochester Accelerator Pump

They usually worked pretty good. When actuated, the pressure of the gasoline under the plunger would push the leather tight against the bore.
Some of them had a circular spring on shaft under leather to keep leather tight against bore. Salvage spring from the old one if it had one.

If not, I would soak the leather in engine oil to soften it, so it does not crack, and then flex it backwards to expand it out a little.
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Old 11-08-2016, 01:57:28 PM
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Craig A Craig A is offline
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Default Re: Rochester Accelerator Pump

What color is the new "leather"?
In the kit I got from Mikes Carburetor Parts it's blue.
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Old 11-08-2016, 06:50:45 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Rochester Accelerator Pump

You do not want rubber on the accelerator pump piston - crap alcoholized gas will ruin it in short order! Even if you do not use E-10 crap gas, the winter additives the gas companies are now using are just about as bad! Follow Power's instructions, and you should be good. it usually takes a little time for gas to soak and slightly swell the pump piston. Soaking in engine oil or ATF will soften and allow it to better fit the bore of the cylinder, if it is not worn too badly As Power suggested, if the new piston does not have an expansion spring, take the one from the old piston and install it on the new one..
Andrew
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Old 11-08-2016, 07:54:51 PM
carbking carbking is offline
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Default Re: Rochester Accelerator Pump

Quote:
Originally Posted by Andrew Mackey View Post
You do not want rubber on the accelerator pump piston - crap alcoholized gas will ruin it in short order! Even if you do not use E-10 crap gas, the winter additives the gas companies are now using are just about as bad! Follow Power's instructions, and you should be good. it usually takes a little time for gas to soak and slightly swell the pump piston. Soaking in engine oil or ATF will soften and allow it to better fit the bore of the cylinder, if it is not worn too badly As Power suggested, if the new piston does not have an expansion spring, take the one from the old piston and install it on the new one..
Andrew
The leather pumps should have the expander spring.

Rather than using engine oil for pre-soaking the leather, use a light machine oil (3 n 1 oil, sewing machine oil, etc.). ATF will work as well.

And generally, a 50-year-old leather pump can be soaked, and will outperform ANY of the modern synthetic pumps, regardless of their color. Of course, if the leather has been damaged, the above statement is not true. Soaking the leather will not repair the damage.

Jon.

---------- Post added at 05:54:51 PM ---------- Previous post was at 05:49:17 PM ----------

Sorry for second post. Wanted to edit the post above, but guess I am technologically challenged

The band around the leather mentioned by the original poster served a double purpose. First, as suggested, it provided protection for the pump. Second, it serves as a guide to help insert the pump in the pump well. Once the leather has been oiled, replace the cardboard band on the pump, place the pump over the pump cylinder, and push the pump out of the cardboard band. The cardboard will allow the leather to be pushed in the pump well without damage (kind of like using a piston ring compressor).

Jon.
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Old 11-08-2016, 08:23:04 PM
Amax Amax is offline
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Default Re: Rochester Accelerator Pump

Power is correct. Just give it some time. It will be fine.

Recently went through the same thing myself. Rebuilt a single barrel Carter with a 50 year old NOS leather plunger. I used engine oil and then gas to swell it up but in the end it just needed to inhale on its own. On the bench it would not pump at all and in the car it pumps so well I had to back off the adjustment to the lowest setting.
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Old 11-10-2016, 08:05:41 AM
TomBall TomBall is offline
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Default Re: Rochester Accelerator Pump

I got the kit from Mike's Carb(I think). The leather color was brown. I softened it in 2 cycle gas. It did not need the band to install it in the carb bore. The spring was inside the cup but it didn't seem to push out on it. I'm pulling it back out today to see what can be done.
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Old 11-11-2016, 06:19:14 PM
TomBall TomBall is offline
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Default Re: Rochester Accelerator Pump

I took it apart and massaged it a little and now it works fine. Thanks to all who responded.
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