<VV> Electric Fuel Pumps - One opinion (long)

[Sethracer at aol.com]

In a message dated 3/14/2007 5:26:12 A.M. Pacific Standard Time,  
tconnolly at iepfire.com writes:

I am  getting ready to have my 64 110 converted to electric fuel pump and 
would like  to hear any experiences people have had with various units.
1.  Reliability.
2. Noise, I have heard some can be annoying.
3. Possible  experienced failure rate.
Thanks,
Tom  Connolly




Tom - First, you are doing the right thing by asking for input before  
plunging ahead. You will be provided with a lot of experience and opinions  for you 
to sort through. At the time of the Corvair's design and  construction, 
electric Fuel pumps were not very common, except in a few British  cars. Mechanical 
fuel pumps were pretty much universal. Electric pumps were  not particularly 
reliable (See "British cars" above.) The Corvair mechanical  pump was 
originally very reliable, and may now be again. A number of years ago,  some bad 
material, or more correctly, the wrong material was used in  manufacturing a large 
number of aftermarket pumps. At about the same time, age  caught up with the 
original design and construction of the pumps. Eventually,  even the original 
mechanical pumps can fail. In the car, through fatigue of the  diaphragm, or via 
an internal  valve popping out or still in the  box, the screws can back off, 
causing a brand new pump to leak  gasoline out onto the motor. The diaphragm 
failure was usually more insidious,  since failure usually caused gas to leak 
into the crankcase of the motor,  contaminating the oil. This was usually 
discovered when the oil level started  rising when checked on the dipstick. The 
real tell-tale was the smell of the  contaminated oil. This is when the 
controversy started. By the 70's, many more  cars started using electric pumps. GM 
started using in-tank pumps even before  Fuel injection (which required electric 
pumps) became universal. Generally  speaking in-tank pumps should not be used 
externally because they are designed  to be cooled by surrounding fuel. All 
electric pumps have to use some mechanical  method for moving the fuel along. 
Some have a spinning electric motor, some have  an electric solenoid which kind 
of duplicates the design of the Corvair's  original pump, using a pair of 
check valves to capture and push the fuel along.  Factory electric pumps usually 
had an extra circuit or two added for both safety  and long term pump life. 
Most electric pump applications are designed to  pressurize the fuel system ahead 
of the injectors. A fuel pump relay, including  a pressure switch, controls 
the power to the pump, allowing the startup  pressurization of the system, and 
the cutting off of the pump if the ignition is  shut down. In addition to 
this, most vehicles have an impact switch set to  remove power from the pump after 
a collision, this keep the pump from  adding fuel to the flame as a result of 
a hard impact. I guess you must feel  like the guy who asked what time it was 
and was told how to build a watch! But  here is the bottom line. There are 
two basic types of electric pumps, rotary  pumps and diaphragm pumps. The rotary 
pumps make a whining spinning noise, the  diaphragm models make a thumping 
sound. Both can be annoying. The best method of  isolating the noise is by 
choosing the best location, then keeping the noise  inside the pump by putting 
something between the pump and any chassis appendage.  I have mounted pumps in the 
area directly below the fuel tank and wrapped the  pump in a sound absorbing 
material. That worked for me. I have also, for a  racing application, mounted 
a rotary pump on the inner panel of the  front trunk. The result was a bit 
noisy, but worked fine. Remember that it is  recommended that the pump be mounted 
below the fuel level in the tank, most  electric pumps are reasonable fuel 
"pushers" but lousy  pullers.  
The most common installation is behind the tank, tucked in where debris  
under the car won't snag on something. If wrapped in some kind of foam or audio  
sound attenuating material. If you put an automatic shut-off valve, having it  
controlled by oil pressure is one way that folks do it, you might want to add  
either a microswitch to allow the driver to bypass the cut off or a switch 
act  as a secondary cut-off. This can also be an effective anti-theft device. 
Since the Corvair is a reasonably "frugal" vehicle, it doesn't use much gas  
and so almost any pump will provide the oomph you need. Just try to  minimize 
the noise - both at the pump and where you can actually hear it - in  the 
drivers seat. I have used several different rotary pumps, but all were for  race 
cars and all were pretty loud. My current pump installation is a small  
in-line, wrapped in foam rubber, and powered through the ignition lead but  finally 
controlled by an auxiliary switch hanging under the dash on a  switch panel. - 
Seth Emerson 
  
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