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post #16 of Old 05-13-2019
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Re: Fuel lifting pump making noise when first starting engine

Originally Posted by Cassidy View Post
Typically a Yanmar has a fuel bypass that sends excess fuel that the engine doesnít need to run, back to the tank. Well, at least the 4-cyl ones do, no reason to think the smaller ones are different.

So if the engine switch is on and the engine isnít started, the pump you describe will continue clicking interminably as the fuel cycles back to the tank. These pumps click each time they deliver fuel, yours may click more frequently while the engine runs as a result of the through flow system.

I installed a diesel flow pump normally fitted to a Ford Explorer, pumps adequate volume for a 4JH4E and gently buzzes in the background. The downside is that the fuel is warmed by the through-flow and brings the temperature of the whole fuel tank up. I havenít had problems yet but I often wonder about condensation, diesel bug and all those other horror stories.
the Yanmar does have a return line on the 4 cylinder and smaller engines but it is from the high pressure injectors and not the lift pump side of the injection pump so it only returns fuel when the engine is running. the reason the engineers have the fuel return back to the fuel tank is to cool the excess fuel that is coming back from the hotter fuel injectors. most Yammers have a mechanical engine driven lift pump and really don't need an electric lift pump unless the tank is placed to low in the system to meet the Yanmar requirements.

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