<VV> Electric Fuel Pumps vs Diaphragm

[BobHelt at aol.com]

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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