Help - got a fuel pump leak - PeachParts Mercedes-Benz Forum

#1 02-13-2003, 01:40 PM

Got gas pouring out of a little hole on the side of the fuel pump on my M180, '69 W114. Looks like a vent hole but maybe not. Does this mean I've just bought a fuel pump? Or could it be just the diaphgram? And all this time I was blaming the Zeniths! Thanks.

Mark DiSilvestro · #2 02-13-2003, 01:50 PM

If your pump is the type that can be dissassembled AND repair parts are still availible, you could rebuild it. I'd get a new one. Replace the fuel filter too.

Happy Motoring, Mark

Mark V · #3 02-13-2003, 05:43 PM

I checked and the diaphram was available through the dealer at, I think $90 (cdn). However, it was a 2 week delivery. I got one used cause its a daily driver.

Mark
69 230

ctaylor738 · #4 02-13-2003, 06:57 PM

If gas is coming out of the hole, you need a new diaphragm or a new pump. I THINK that the newer one-piece pump replaces the rebuildable one on all engines of this vintage.

ctaylor738 · #5 02-18-2003, 09:06 AM

I had the old style on an M130 engine, and replaced it with the new style.

Good call about the gas in the oil.

Douglas Broome · #6 02-26-2003, 03:29 PM

That is a vent hole. It exists to equalize the air pressure behind the diaphragm. When a good diaphragm operating, air is drawn in and expelled through that vent hole. Thus the diaphragm is devoting its entire work to pumping fuel, not fighting vacuum or pressure on the opposite side.

When gasoline flows out of this vent hole, it signifies a rupture in the fuel pump diaphragm hence total pump failure. Pumps are normally rebuildable. If you cannot find a rebuilding kit at Mercedes or elsewhere, contact me off list for a source of individual rebuilding parts. These are basic AC-style pumps.