<VV> Electric Fuel Pumps vs Diaphragm

[Western Canada CORSA]

You learn something new on <VV> all the time.  Seven years on <VV> and I did
not know about the "dam" in (some of) the mechanical pumps!

Regards,
Joel

-----Original Message-----
From: virtualvairs-bounces at corvair.org
[mailto:virtualvairs-bounces at corvair.org] On Behalf Of BobHelt at aol.com
Sent: Saturday, September 01, 2007 10:29 PM
To: john at nfdc.net; virtualvairs at corvair.org
Subject: Re: <VV> Electric Fuel Pumps vs Diaphragm


 
In a message dated 9/1/2007 8:12:31 PM US Mountain Standard Time,  
john at nfdc.net writes:

With the  2 failures, my confidence in the "old style" diaphragm pumps is
not 
very  high.  Suggestions and opinions would be appreciated.

John  Johnson



Hi John,
It pretty much boils down to your preference. Tjhere are a lot of people  
complaining about failures of the mech pumps. But if you carry a few spares
and  
can change pumps easily,  that can be your solution. Electric pumps seems
to 
have a much lower failure rate.
 
But let me explain about getting fuel into the crankcase. ALL Chev supplied

pumps had an internal dam built into the lower casting that directed any
such  
leakage to be expelled outside the pump via a small exit hole on the side of

the  pump. It's not good to have fuel being sent outside the pump and
landing 
on the  rear motor mount....but at least you can see the fuel and smell it. 
This  essentially prevents any fuel from getting into the crankcase. Some of
the 
 aftermarket manufacturers of pumps eliminated this dam. Thus getting a  
cankcase full of gas on occasion.
 
For any mech pump that you intend to use, separate the parts and check for  
this dam. The Corvair Tech Guide Supplement has a sketch.It is a raised
portion 
 around the central hole of the lower portion. If the lower portion is 
completely  flat, it doesn't have the dam. Before you disassemble any mech
pump 
scratch a  vertical line on the outside so that you can get the orientation
of the 
pieces  correct for reassembly ( the screw holes are NOT uniformly spaced.)
Regards, Bob Helt



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