fuel pump diaphragm and gaskets

[richard1216]

I have an '86 50hp Merc 4 cyl. I just bought 2 sets of fuel pump diaphragms and gaskets for the fuel pumps. I notice there is a thin nylon diaphragm (?) in each pack along with the regular rubber ones. The existing fuel pumps only have the rubber diaphragms. Should I install the nylon ones along with the rubber ones? If so, in what order do they go on? I am not sure if the nylon would go against the fuel pump body or between the rubber and the gasket. Thanks for any help!

 

[cmayhle]

Re: fuel pump diaphragm and gaskets

I have exactly the same question, only for a 1976 500, 50 Merc. My "extra" nylon diaphragm matches the profile exactly of the rubber check-valve diaphragm. Anyone know what this is for?

 

[cmayhle]

Re: fuel pump diaphragm and gaskets

I have an '86 50hp Merc 4 cyl. I just bought 2 sets of fuel pump diaphragms and gaskets for the fuel pumps. I notice there is a thin nylon diaphragm (?) in each pack along with the regular rubber ones. The existing fuel pumps only have the rubber diaphragms. Should I install the nylon ones along with the rubber ones? If so, in what order do they go on? I am not sure if the nylon would go against the fuel pump body or between the rubber and the gasket. Thanks for any help!

richard1216, after further research I have been told that these fuel pump diaphragm/gasket kits are used by multiple models that may or may not use all of the pieces, so just match-up and replace those that apply to yours. Hope that helps out.

 

[richard1216]

Re: fuel pump diaphragm and gaskets

thanks for the info. I also was told that the ethanol in some gas will deteriorate the rubber diaphragms, hence the nylon ones. I have found a gas station in my area that sells non-ethanol gas, and have been using that only for my outboards, moped and lawn mower. Thanks for your help. richard

 

[Faztbullet]

Re: fuel pump diaphragm and gaskets

PULSE FUEL PUMP:
The new repair kits contain check valves made of a plastic material, impervious to damage
from fuel additives. When repairing the fuel pump discard old rubber and small plastic check
valve disks, and install one new plastic disk under each retainer. Caution must be taken not
to push the check valve retainer too tightly against the check valve, this may cause the valve
to deform.
NOTE: Before driving the check valve pin into the retainer, support the pump housing on
the opposite side, directly below the check valve retainer using a socket or spacer. This will
prevent distortion or cracking of the pump housing.
http://www.marinemechanic.com/merc/distributors/mercurymarine/outboard/fuelrestrictiontesting.PDF

 

[cmayhle]

Re: fuel pump diaphragm and gaskets

PULSE FUEL PUMP:
The new repair kits contain check valves made of a plastic material, impervious to damage
from fuel additives....

Thanks kindly for that information Faztbullet. If possible could you translate this to my application? My 1976 Merc 500, 50 has (2) Integral Carburetor Type fuel pumps. The repair kits (#5137) each have (2) rubber diaphragms that match-up to the original service manual exploded-view: The Pump Diaphragm and the Check Valve Diaphragm. However, only the Check Valve Diaphragm has a duplicate made of the nylon/plastic material. Wouldn't both of the diaphragms be subject to the same fuel conditions, and if so why do you suppose they would only include an updated alternate piece for the Check Valve Diaphragm?