Saturday August 16, 2025
Fuel System Calibration, Flushing, Testing
(2.0 Hours Firewall Forward, 2.0 Hours Fuel Tanks)
4.0 Hours Total

I bought a bunch of gas cans for the process of filling the fuel tanks and doing the fuel level calibration. I had the fuel truck come and fill these cans up for a total of ~22.5 gallons. Then I slowly added 2 gallons of fuel to each tank at a time and recorded the calibration set points in the G3x in both level (in-flight) and tail-on-ground attitudes.

Once I had 10 gallons in each tank, I flushed the fuel through for about 15 minutes using this cheap electric automotive fuel pump with a filter on it. It was connected to the output of the fuel selector, so the plane's electric boost pump was excluded. The point of this is to filter out any junk remaining in the fuel tanks from the build process.

Right tank first...with the fuel just pumping around in a loop.

And the left tank.

Then I had the fuel truck fill all of my gas cans again and I finished filling the tanks in 2 gallon increments. I don't think the capacitive fuel senders are particularly accurate, but they're close enough.

Then I did a fuel flow test by disconnecting the hose at the firewall and redirecting into a fuel can with this aluminum tubing. I forgot to take a picture while it was attached, but this is essentially what I did. The electric boost pump appears to be capable of pumping at ~70 GPH with the plane in a climb attitude, which is far greater than what the engine needs at full power.

Then I popped the injector supply lines off of each cylinder and pumped fuel through into some plastic containers. I got fuel pressure in the green during this and all four injectors dribbled fuel.

Here are the other two... I discarded this fuel because there was fuel remaining in these lines from the factory test stand run and that gas is now almost two years old.

Finally, my battery had run down a bit because I'd left the G3x on for several hours while calibrating the fuel levels. So I charged it up with my 30A power supply.

I think I may fire up the engine tomorrow...

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