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Fuel Pump Replacement

Had a problem where the Cosmo would just shut down. No codes were recorded. It appeared to be something in the fuel supply system. The obvious place to start was the fuel pump (although the problem ended up being elsewhere).



The replacement pump chosen is a Walbro GSS 342 which is 255 litres per hour, supporting up to approximately 370KW - well and truly enough for my needs.
(Note: the Walbro GSS 341 has the inlet / outlet piping offset 180 degrees from the GSS 342 and would NOT be suitable for the Cosmo.)


  The pump came with a universal kit (Walbro # 400-766) which includes:
- electrical connection
- hose and clamps
- rubber isolator
- filter.


  First step, remove the fuel tank as detailed here.



The unit on the bench.

Note the top pipe connection utilises a bell compression fitting which will need to be removed to suit the Walbro.

Also note the capacitor across the wiring for suppression of electrical noise (likely to affect your radio, etc).

The rubber isolator at the base of the pump sits in a metal "L" bracket.



The isolator at the base of the tank insulates the pump from the body, reducing noise and vibration.

To get the Walbro isolator to fit the original bracket it is necessary to trim some of the rubber away for a good fit. Some conservative trimming will result in a firm fit making a secure mounting base. The 5/16 hose over the pipework will provide substantial top support.

When installed, the bottom of the Walbro isolator and filter is 2-3mm lower than original. This prevents the assembly from being installed into the tank with the "L" bracket at its original 90 degrees. It is necessary to bend the "L" bracket slightly to prevent the filter / isolator from fouling on the base of the fuel tank.





Next, off comes the compression fitting. It is best to cut the pipe directly above the bell fitting to allow as much hose as possible to slide over the piping. This is better for both rigidity and sealing.

Be sure to file the end of the pipe and to ream the inside.

Take particular care to clean off ALL metal filings from both the inside and outside of the pipe and also off all of the fuel pump bracket assembly.




The wiring.

It's naturally very important to get the polarity correct. Blue is positive on both the pump and capacitor wiring with black being negative.

I went for soldered connections with two layers of heat shrink.


  Here is the finished article ready to go back in the tank.