After the first few flights, I had Malcolm open up the fuel filter and clean it out. I cleaned out the tanks as best I could before and after they were sealed, but you can never get all the debris out. So cleaning out the fuel filter after a few hours is called for.

Malcolm reported the usual amount of crud that he sees in the filter at this stage.

At about the 15 hour mark on my Phase I flight testing, I had a cylinder come up cold during the runup. Now I’ve seen this more times than I count.  It’s always a fouled plug that is usually from idling full rich for too long.  The standard approach is to run up the engine and aggressively lean engine.  And has so many times in the past, it cleared the fouled plug.

But then about two flights later, I had two cylinders come up cold on the run up pad. Now that’s one I haven’t had before. I leaned out the engine at run up power to no avail. After a few more attempts the cylinders were all firing properly again. I made a mental note to make sure and lean the engine for ground operations like I have been with the Cessna.

Two flights later, it happened again. But this time I was only able to clear one of the cylinders. So I checked the mags and discovered that the cylinder was dead for both mags.  When it’s a fouled plug, it’s usually the bottom plug so I should have seen power on the top plug. Which meant that it must be a fouled (clogged) injector. Oh well.  Back to the hanger.

I pulled the cowling and removed the injector for the offending cylinder and sure enough, it was clogged. I could not see light when looking through it. I got a paper towel and blew through the injector but it wouldn’t clear. I tried a few more times and still couldn’t clear it. While I was walking over the service center, I tried a couple times and it finally cleared. But since I didn’t have the paper towel over the end, I wasn’t able to identify what the material was.

I reinstalled the injector and cranked up the engine and all six cylinders were firing away so I made another flight.

The next morning when I started up, I had two more cylinders that were not firing. A mag check showed that it wasn’t the plugs which meant that I had two more fouled injectors.  So I called Malcolm to come out and give me a hand. While I was pulling the five remaining injectors he was removing the fuel filter.

I cleared out the injectors and then I heard Malcolm say “Check this out”. I looked at the fuel filter in his hand and it was about half full of crud. He cleaned it and this is what came out of the filter.

He said that was two to three times what he found the first time he cleaned the filter. Our guess is that there was a pocket of fiberglass dust that was stuck behind one of the baffles and that after about 10 hours of flying it got flushed out.

When the filter was reinstalled, we disconnected the fuel line at the servo and directed it into a container. Then I ran the fuel pump for a few seconds. We got a small amount of crud. Emptied the container and did it again. Clear fuel this time.

Hooked the fuel line back up and the engine ran fine.

So I’m going to be checking the fuel filter about every 5 hours for the immediate future until it shows clear.