Originally Posted by never monday
there is if the diaphragm of the mechanical pump is ruptured.
There is virtually no chance that will happen. Lift pumps have poppet (one way) valves that let the fuel into the diaphragm chamber and then another one way valve to pass the fuel on down line. Pass through fuel from an electric pump will have no effect on the operation of the mechanical lift pump.
- - The diaphragm in a mechanical lift pump will wear out, crack, get stiff and eventually stop pumping fuel. If it is split/cracked then pressurizing the fuel system will result in fuel dripping or draining from the mechanical lift pump casing. Which is very good to know as you can then rebuild
the lift pump or bypass it with a piece of fuel hose and some hose clamps. The Walbro pump will supply fuel to the diesel engine and that will get you to a safe harbor where you can fix the thing properly.
- - I have two Walbro's in my fuel system, one for pressurizing the engine system downstream from the main Racor
filters and can also be used to recirculate the diesel back to the main tank after passing through the main Racor filters (polishing). The other is at the main diesel tank and pressurizes the entire fuel system for leak checks and bleeding of the high pressure pump.
- - Mechanical lift pumps are left over from the car/truck old days when everything had to be mechanical. The newer engines use small electric pumps and save all the cams and levers, etc. involved in a mechanical pump. But still I would be sure to have a spare electrical
fuel pump specific to that engine stored away in the bilge
just like I keep a spare rebuild
kit for my mechanical lift pump stored away.
- - Currently Walbro diesel pumps are the only rated (UL approved) diesel pumps for marine
use. There may be others outside the USA but as of a few years ago - Walbro was "it" for the USA.