If required the FF-3 can interface to standard automotive fuel level sender(s) as indicated. Most of
these senders are resistive types.
Capacitive types can be used provided they have a voltage output not exceeding 5V. The level
terminal has an internal 1K resistor pull-up to 5V.
Please note that capacitive senders may exhibit large errors as they are very sensitive to the
composition of the fuel used. We do not recommend using capacitive senders with automotive
fuels for this reason.
Please ensure that the float of the level sender moves freely at all times and that the float is large
enough not to remain submerged in case the mechanism becomes sticky. This will result in an
incorrect indication of fuel level.
Note that you need to perform the calibration routine as outlined in the respective section of this
manual.
Please observe the installation notes supplied with the fuel flow sender. Should you install a
different fuel flow sender to that supplied by MGL Avionics, ensure that you enter the K-factor
relevant for your sender.
Some senders require a pull-up resistor to the 12V supply line. We find most installations of these
senders require a 4K7 pull-up resistor.
In all cases ensure that fuel flow through the sender is continues and smooth. Nearly all flow
sender related problems are due to choosing a bad position in the fuel supply line. Any fuel flow
sender will be negatively effected by having to measure pulsed fuel supply such as is created by
most mechanical or pneumatic fuel pumps or by carburetor float valves that open and close
continuously. Nearly every installation would require a suitable fuel reservoir to help create a
smooth fuel flow for the sender. This can be easily created by installing a fuel filter before
AND
after the flow sender.
IN ALL CASES OBSERVE THE FUEL FLOW MANUFACTURERS INSTALLATION
REQUIREMENTS
Be aware of possible problems with fuel tanks made from fiberglass. Some of the resins
used may leach chemicals into the fuel when the fiberglass is new. These chemicals may
interfere with the operation of your fuel flow sender, even causing it to stop producing an
output signal. The only remedy is to open and clean out your fuel flow sender.
