I am about to replace the fuel pump on a C3 and noticed the holes in the top silver portion of it. My dumb question is why are they there and wouldn't they leak fluids. Thought I would ask the informed souls on this board before I spend the time putting it on as I am unfamiliar with the internal workings of these. I have included a view of the pump and the holes are visible on the boss and on the band above the bowl. On the reverse side these holes are sealed. Thanks in advance.
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Re: AC fuel pump question
The holes are vents, if the diaphragm ruptures (this is a common pump failure) fuel will leak out of the holes and not be forced to enter the cylinder case. They do not normally leak here because all the fuel is sealed below the diaphragm. -
Re: AC fuel pump question
Gary and Charles-----
Yes, the holes are vents. However, their purpose goes beyond being just being "dump" orifices if the diaphragm fails. In fact, that's just a "secondary" function. Their primary function is equalize pressure on the upper side of the diaphragm and maintain it at ambient.In Appreciation of John HinckleyComment
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Re: AC fuel pump question
I knew that the board would smack that one out of here like a big fat curveball. I guess my only question now is if fuel can't enter the engine because of the diaphragm, pressure and the presence of the holes what keeps oil from leaking down and out these same holes. Oh yeah, and what are you doing Saturday for about 2 hours? P.S. bring a torque wrench.Comment
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Re: AC fuel pump question
Charles-----
There is a "secondary" diaphragm-like oil seal on the top of the chamber above the main diaphragm. The vent holes are into this chamber (i.e. between the 2 diaphragms). If the upper diaphragm/seal fails, you may well get oil out of the vent holes. It's still a rather "circuitous" route for the oil to get into this chamber and out the holes, but it can and does occur.In Appreciation of John HinckleyComment
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