2 steps forward, 3 steps back

Where to start?

As the engine was running sweet using fuel from the Jerry can then I assumed it would run sweet from the wing tanks now that they were cleaned.

How wrong!

A second lot of ground running from the wing tanks gave exactly the same symptoms as before, 'catching' when I changed throttle settings and generally not sweet, smooth running.

This was using the master fuel pump rather than the backup pump - which we know is damaged in some way. In fact when I did try the backup pump this time it died completely.

I've been filming the Dynon so I can analyse the readings later on at leisure.

Compare the readings below to see the difference - the fuel pressure is different in the second lot of running which would indicate a flow restriction in the wing tank to fuel quick disconnects at the wing root. From the first test we know that the flow is good from the wing root to engine and back as it ran sweet from the Jerry can.

Funnily enough the tank pickup to wing root is the only area of fuel line that I did not flush out so perhaps the restriction lies in the flop tube pickup - which does have smallish holes in the brass end.

Despite the apparent sweet running from the Jerry can you can see that the fuel pressure is still slightly above normal - which should be 43.5 psi according to the UL Power manual. It's 49 psi from the Jerry Can and 53.4 psi from the wing tank. Max permitted is 55 psi.

The fuel lines I am using are above the minimum diameter required so I'm not sure why the pressure is so high.

Anyway we will get to the bottom of this problem eventually but now onto the other problems!

I tried to calibrate the fuel sender but moving the min level dial had no effect to the gauge. After reading the instructions again I remembered that I shortened the fuel probe - which is okay to do - but you must re calibrate the sender when you do so. This can be done with a Multimeter which I rigged up but again it did not work. A further investigation with the Multimeter revealed that the sender wire (which should only have a reading of 100mV or less) was reading 11.7 volts so there is a mistake I've made with the wiring somewhere along the line that is pushing battery voltage levels through the sender.

Something to investigate when I take the instrument panel off, which I have to do anyway as I have to wire up the Red Cube to the Dynon for fuel flow info.

Another problem was with the gear leg fairings which sit at the top of the gear legs and fair in the leg to fuselage junction and cover the hole there. As you already know these do not fit the fuselage very well at all and are tight on the gear legs. I stupidly fitted them with the fuselage upside down and with no weight on the legs, so the holes I have tapped into the legs for the attachment of the securing bolts are never going to line up now that the gear has the weight of the aircraft on it.

I was thinking of doing what Adrian Hatton did and securing the flat plate area of the fairing to the fuselage and then leave the bit further down un-fastened so that this becomes the area that moves when the gear flexes but Pete Wells warned against this saying that I need to use the factory method as the gear leg flexes so much that it will crack the fairing. 

So I've put flock into the old holes and will redrill and tap out new threads for the securing bolts soon.

And now the final problem - we always save the best (worst) for last!

After the second lot of ground running I returned to the airfield to find yet another fuel leak from the Starboard wing tank. This is not coming from the same area as before as I pro sealed the inside and outside of the securing bolt this time and this area was dry - no leaks.

The leak is coming from the tank somewhere. quite low down as I found when I was draining it and monitoring if the leak was still coming out or not. 

If I'm lucky I think it will be coming from the hole made for the fuel drain and tank vent. This is the logical first port of call as there was a hole made in the tank for these items to be fitted and if there is the tinniest of gaps in the flock then a small leak would happen. It is indeed a very small leak as the speed of the fuel coming out was very very slow. 

Anyway so that dripped out all over the fuselage bottom and stripped the paint off again just like the other side (the previous leak happened on the Port side).

So now we have matching shittyness underneath on the black paint. No problem here as the fuse base has to be repainted anyway in it's entirety. This just proves that the wing root area and fuselage base were not painted correctly all over.

Hopefully I will have a more positive post next time round.

Trying to calibrate the fuel sender - I had to jury-rig up these wires to connect up the sender to the power source and give access to the dial on the sender at the same time.

1st ground run from Jerry Can after sustained full power run and back to warm up revs - fuel psi is okay here.

1st ground run from Jerry Can at Max Static RPM. Good that the oil temp stabilises at this figure but bad that the fuel pressure is so high at 49 psi. Still running sweet at this though.

2nd ground run from Wing Tanks this time. Note the higher fuel pressure. 53.4 psi now. This is from the start of the run so the CHTs and EGT's are lower.