• Re: Fuel pressure rise

    by » one month ago


    According to the Flight Design Maintenance Manual Supplement S3 (for injected engines), the only coarse filter is in the gascolator, which is between the header tank and fuel pump inlet.  Any larger debris leaving the tank would get caught in that filter before reaching the pump or the fine filter.  If that happened, it would create a fuel supply restriction and your fuel pressure would fall, not rise.  Directly after the fuel pump is the fine filter, then after that is the fuel pressure sender. So, with the sender located downstream of the fine filter, your fuel pressure rise cannot be attributed to filter loading. But I would make sure that's where it is located. 

    If the Flight Design Manual is correct, in addition to a fuel tank selector valve, there are fuel shut off valves in front of the fuel pump that can shut off both the supply and return lines to the pump and effectively stop the fuel flow before the firewall. It appears both supply and return valves are operated with a single handle. With what you are experiencing, I would check these shut-off vales carefully to make sure the return line valve is opening fully. The valves are located in the center console next to the fuel flow transducers. 

    The way the system is plumbed, this almost has to be one of the following:

    * Restriction in the return line or return line valve. Return line pressure should not exceed 7 PSI. 

    * Fuel sender error, either the sender itself or wiring

    * Fuel pressure regulator failure (Rotax Engine Part)


    Take a look at section 28.00.0 of the Manual Supplement at the link below. 

    AF04800011_02 (flightdesignusa.com) 

  • Re: Fuel pressure rise

    by » one month ago


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