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And here's the last chapter to this entertaining troubleshooting event...
This morning, my engine guru managed to pull himself away from his wife's honey-do list for some man cave time. We snuck away to my hangar to get to the bottom of this mystery. We began by pulling the injector from all four cylinders. Using brake cleaner and Q-tips, this is what we got :eek: ![]() Based on the stuff found in the injectors, we backed up to the inlet filter in the fuel servo, where we found more cruddies. The crud found in the inlet filter had the look of fine-hair fiberglass mat. Based on the CRUD found in the fuel servo, we backed up to the fuel filter located upstream of the electric fuel pump. We found larger chunks of debris. The debris was smearable black material. The amount found in the fuel filter was not very much. It may have blocked about 1% of the fuel filter. The dismaying part is that the fuel filter had been cleaned during my last annual about 20 engine hours ago! Based on the black, smearable material found, we postulated that it may be ProSeal that may be breaking off in the tanks and migrating through the filters. If you remember from a previous post in this thread, I run MoGas most of the time. (non-alcohol Premium grade) So I drained both fuel tanks, and allowed them to dry out for awhile. Using a q-tip taped to a long stick, I swabbed several ProSeal locations inside the tanks to see if there was any softness or failure in the ProSeal. I didn't get any smearing of the ProSeal. Next, I hooked up a fuel pump to the fuel tank sump, added five gallons of AvGas, and recirculated the fuel (through two in-line see-through filters) back to the tanks for about an hour. The filters did not seem to get any dirtier, but I did not cut them open to examine the media up close. Finally, I filled the tanks with AvGas and went up for about twenty minutes of pattern work. Everything ran fine at this point, and I'm almost done with this chapter. My last action item will be to open up the fuel spider, remove the diaphram, and clean out the orifices in the spider to make sure that there's nothing left in the system. Although I've been flying for 480 hours on MoGas, I think that I'm going to have to stick to AvGas. I don't know if I got a bad batch of fuel that caused all of this trouble, or if this was building up and just finally reached a peak. (I think it's the bad batch of fuel - based on cleaning all screens and filters just a few hobbs hours ago.) |
Scott, you're fuel filter is the problem, not the mogas. Its not fine enough to catch the crud that is making its way upstream.
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Scott,
Would you mind posting what fuel filter you are currently using? Thanks, David |
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I have the standard fuel injection system from Van's with the Airflow Performance fuel filter. ![]() |
Good job but.....
Hi Scott,
While all this stuff if bad I would not assume that it was the cause of your problem.......it may be, but for you loose a cylinder, the fuel feed to that cylinder would have to be temporarily cut off. Compression, fuel and a spark are the three things you need, so a sticky valve could still be the thing that actually caused it. I have often come across situations like this where you think you have found the culprit only for the problem to occur again, so take care for the next few flights. |
The MoGas - do you transport it by some means to your airplane? If so I would look at these items first.
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Where to source?
Walt, where to you get that 74 micron filter and will it fit in the Airflow performance housing? Is the pressure drop much more to affect vapor formation? Thanks.
For reference: Oil filters ~ 30 micron Diesel prefilters ~ 15 micron Diesel fuel filters ~ 5 micron |
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See posts 28 and 29 in this thread for info from Don at AFP regarding the filter screen size:
http://www.vansairforce.com/communit...=Filter+screen Erich |
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