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im taking over a build that is 90% done. previous guy started to install an inline solid state electric fuel pump in addition to the mechanical engine driven one.
is this a common mod?
should there be a bypass so that if the mechanical pump fails, the mechanical one can still suck fuel?
can both pumps run at the same time or is the electric one just in case an emergency?
thanks; Paul
Paul,
A number of builders have installed a Facet Electric pump in line with the mechanical pump on the 912 ul/uls engine - primarily as a backup to the mechanical pump.
There are a couple versions of the Facet electric fuel pump (unless the one you have with the kit is not a facet) It is important to have the pump version which has a low enough pressure so as not to flood the engine...I believe 4 to 5 psi is correct.
The Facet pump has to be mounted low - ours is located under the console near the firewall - the pump is designed to push, not pull.
The reason for having it, or not, depends on builder preference. The airplane fuel system is designed well enough, if it is maintained, so that it is reliable without a boost pump.
I run it before startup to be sure the fuel system is pressurized; but, turn it off before starting so I know the mechanical pump is working. I do not run it otherwise, but would if the fuel pressure dropped off. A backup electric fuel pump won't correct all possible failure modes of the mechanical, but it would cover some such as malfunctioning poppet valves in the mechanical pump; or, may help with a partially clogged fuel system or filter.
I have a model IV with the 912ul. I installed a Facet electric pump as close as possible to my header tank. It's actually under the left seat. At the time, I felt it was good insurance to have a backup but my main purpose was to pressurize the carbs before startup. I always turn it on before a cold startup and it always starts good. I always leave it on for takeoff and I usually forget to cut it off during my flight. It flows just fine with just the engine pump, it doesn't stop flowing when it's cut off. Make sure you get the right model. You'll want the low pressure type, I believe something like 4.5 psi. I bought mine at NAPA. My plans didn't call for an electric pump but for my peace of mind it's simple to install and cheap. Good luck, James Thomas
thanks guys, that is the same pump i have, ill be keeping it as a backup as well. sorry if not enough engine info, i thought putting 912 ul in the title was all that was needed. ill try the search function next time. Paul