Another Fuel (pump?) Issue

[ArlingtonRV]

I have a 2001 RV-8 with an O-360 that was sent to Lycon for upgrade before installation to include high compression ceramic coated pistons, fuel injection, CS prop and an angle valve sump. I have recently, as in the last 5 or 6 flights, had an issue that somewhat has me stumped.

After flight I will find a small amount of blue stain on the belly just aft of the lower cowl exit.

https://steverush.smugmug.com/VAF-Posts/

During take off, with the boost pump on, I get a very faint fuel smell in the cockpit. It goes away when I turn the boost pump off. Last Sunday I tried flying without using the boost pump and got no fuel smell and no blue stain on the belly.

I pulled the cowl and inspected the fuel pump drain tube and fitting, outlet, gascolator, and all of the plumbing forward of the firewall and there is no signs of fuel leaks anywhere.

Today I went back to using the boost pump as normal and came home to the stains shown above. Fuel pressure in flight is fairly steady between 22-26 psi. It fluctuates a small amount between those numbers and moves very slowly. I verified with the previous owner that it has been that way all along.

Just for giggles I turned on the boost pump in the hangar with the throttle closed and the mixture at idle cutoff and had a dribble of fuel coming out of the mechanical fuel pump drain hose. I got a sneakin' suspicion it shouldn't oughtta do that.

The mechanical fuel pump has been on the engine for 12 years. I am leaning toward a breaking down fuel side diaphragm.

Is there any other item that could cause this problem, or is it a pretty straight forward case of a mechanical pump going tango uniform?

[VA Maule]

Most likely the pump's diframe has given ( giving) out, that is the design warning failure mode .
Yeah I know I can't spell!

[DanH]

Originally Posted by ArlingtonRV

...I turned on the boost pump in the hangar with the throttle closed and the mixture at idle cutoff and had a dribble of fuel coming out of the mechanical fuel pump drain hose. I got a sneakin' suspicion it shouldn't oughtta do that.

The mechanical fuel pump has been on the engine for 12 years. I am leaning toward a breaking down fuel side diaphragm.

Is there any other item that could cause this problem, or is it a pretty straight forward case of a mechanical pump going tango uniform?

You suspect right. It's Tango Uniform.

[alpinelakespilot2000]

Originally Posted by ArlingtonRV

I have a 2001 RV-8 with an O-360 that was sent to Lycon for upgrade before installation to include high compression ceramic coated pistons, fuel injection, CS prop and an angle valve sump. I have recently, as in the last 5 or 6 flights, had an issue that somewhat has me stumped.
...
Today I went back to using the boost pump as normal and came home to the stains shown above. Fuel pressure in flight is fairly steady between 22-26 psi. It fluctuates a small amount between those numbers and moves very slowly. I verified with the previous owner that it has been that way all along.
?

0-360 with 22-26 psi on fuel pressure? The max on my O320 is about 9psi I think. Is that your clue that something is wrong with the pump or is it supposed to be that high?

[Sam Buchanan]

Originally Posted by alpinelakespilot2000

0-360 with 22-26 psi on fuel pressure? The max on my O320 is about 9psi I think. Is that your clue that something is wrong with the pump or is it supposed to be that high?

Original poster stated his engine is fuel injected.

[ArlingtonRV]

Thanks for the confirmation, new pump on order.