Testing Mechanical fuel pump

[yelmrap]

Got a really late start on the season and I'm just firing up the old boat.
Seem to be having issues with the fuel delivery. It's a old mechanical pump, On a 1991 4.3 liter MerCruiser. At this time I do not have the ability to check the outlet pressure of the unit. I ended up removing the inlet hose from the tank and there was no fuel present.
Would it be true that if I turn the engine over I should feel suction on the inlet side of the fuel pump?
When I did this I felt very little if none at all.
I also removed the fuel filter and it was bone dry.

 

[ktbarrentine]

Re: Testing Mechanical fuel pump

Sounds like you've got a possible bad diaphram on your pump. I had a bad diaphram, but it worked well enough to at least put gas up to the carb via the sight-flow tube, so I knew I needed to replace the pump (on a 1990 8 cyl 5.0L, so pretty similar). Seems the ethanol gas these days does not get along with the rubber diaphrams in the fuel pumps.... Might just be a good idea to replace the pump anyway, but that is akin to easter-egging your troubleshooting approach.... There is a troubleshooting chart for fuel probs...now If I could just find it (Don S would have had it here in a pinch!).

Were you able to start the engine by adding a bit of fuel straight to the carb airhorn?

 

[CV16]

Re: Testing Mechanical fuel pump

DonS would have went to the "Adults Only" section and posted this...
http://forums.iboats.com/mercruiser...ow-testing-your-boats-fuel-system-283269.html

Don will be missed. I hope we never lose the info he has posted over the years. I know he helped on all of my families boats!