[DeTomaso] Mechanical fuel pumps

[JDeRyke at aol.com]

In a message dated 3/19/09 3:48:08 PM, wkooiman at earthlink.net writes:

> I have a Holley Chrome.  It is shaped like the factory pump - with two 
> vertical cylinders about 1" in diameter.  It has 1/4" pipe fittings.
> For those who care, there are two main failure modes for mechanical fuel 
pumps. The first is failure of the rubber diaphragm and/or the rubber 
check-valves, often from attack by MTBE or alcohol in the gas. The second is the 
mechanical lever's pivot shaft backing out. I've seen this in two chrome pumps (don't 
remember the actual brand).   The casting needs to be staked so the shaft won't 
come out, and apparently the staking would blemish the shiny chrome, so it 
wasn't done (or wasn't done good enough). Due to oil and heat in the area, glues 
won't hold. 
Finally, not the pump but the pump eccentric on the ed of the cam fails, and 
there are two different possible. The OEM is two piece sheet metal, with the 
inner part driven by a bent tab and held onto the cam by a torqued bolt. The 
outer shell spins freely around the inner, apparently to cut wear on the lever 
end. The second type is a single hardened steel cylinder, held on by the same 
bolt. This is a much heavier assembly and probably causes some frictional 
heating and lever wear. FWIW, I'm still running the 37-yr-old pump delivered with 
our '72 L. It has a hose bib on the inlet and an inverted flare fitting on the 
outlet; not optimum, but....   Cheers- J Deryke


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