Re: Fuel Pump

Posted by 55PackardGuy On 2012/5/12 16:05:55

I puzzled over this glass bowl issue with my vintage boat's inboard automobile engine for years. How does it keep running without fuel at the top of the bowl? I observed everything discussed here and never came up with a satisfactory answer, except that there is enough fuel in the carb when the bowl is not at the top to keep it running.

My first glass bowl had a sintered metal filter disk of some kind that floated on top of the gasoline. I took it out and the bowl did seem to stay full more of the time. I would also periodically "bleed" the air out in much the same manner as described (really messy in a boat, even using a can to catch the overflow). Usually I did this only before starting because it really decreased cranking time.

Then I switched to a pleated filter element that just floated in the bowl. Essentially, this proved to me that there was no way gas could get to the line at the top of the bowl if it was not full: the filter element floated up and sealed ONLY when the bowl was full, so why have a filter at all if the unfiltered gas could get through when the bowl was partially full?

This whole glass bowl "filter" thing is kind of a misnomer. Sometimes a filter element is used, but it's really just a sediment bowl where particles can settle out if they're heavy enough, and a "sight glass" to check on fuel flow, quality, and especially water, which it will also separate out before it gets to the carb--and definitely stop the fuel flow.

It was a stupid setup for my boat, because the sediment bowl sat at the front of the engine where a broken water pump belt could easily have knocked it off its mounting (the bowl glass is so thick I didn't worry about it breaking).

So, the solution? Out of sight out of mind! I stuck on a metal in-line filter (actually two) in place of the bowl and that was the end of that. If it doesn't start, I do the "bleed" thing first-- much easier to do with a line--and if that doesn't work, I just replace the filters, for which I always carry spares. Using two of them adds a little insurance-- the first one in line is most likely the clogged one, and if I only have one replacement, I just replace that one. If for some reason I don't have any replacements, there's enough flexible line to connect just the second one.

I also use an in-line bronze element filter before the electric fuel pump.

But it's an old boat with an old gas tank, and every precaution must be taken. And, of course, I don't care about the "period correct" thing when it could leave me sitting dead in the water.

Come to think of it, have you ever noticed how much "air" there is at times in a clear plastic in-line filter? A whole 'nother kettle o' fish!