All dressed up…

Well, today we were planning on doing the first engine start. We set that goal about 3 weeks ago, and Greg, Kevin, and I have been working very hard to make that happen. And we were very close. In fact, if it weren’t for the failure of the electric fuel pump, we would have ran the beast.

The pump failed in kind of an interesting way. The first time we ran the pump this morning, it worked fine. Then it failed. It still made noises like it was pumping fuel, it drew a reasonable amount of current, it just wouldn’t flow fuel after the first usage this morning. We thought maybe the motor seized, but usually that would draw a high current and maybe pop the circuit breaker. It just really didn’t make too much sense to us, especially since the fuel pump was working well 2 days ago and once this morning. The pump only had a grand total of about 5 minutes of time in operation. So we spent a lot of time trouble shooting to make sure it was the pump. And it certainly is. (We tried replicating the fuel flow test from 2 days ago, and it was clearly not pumping.)

My fuel pump is made by Andair, which is a company based in the UK. I chose it because it is a very nicely engineered pump, but mostly because it was the smallest pump I could find. The location where I have it mounted, under the pilot thigh support next to the fuel selector, depended on its small size. Well the issue with using this pump became clear today. Any calls to the manufacturer for support would have to happen early in the morning because of the time difference, as well as on a long distance call out of the country. Also, it seems as though none of the suppliers in the US stock the pump. They order them from the UK once they have a purchase, then send them to the customer. So at best, you are looking a week to get a replacement if it goes bad (again).

As Greg said today, “I can just see you sitting in Left Armpit, North Dakota with a failed electric fuel pump. You would have 7 days to enjoy the local sights while you wait for a fuel pump to arrive from the old country.” He is right. So we called up AirFlow Performance. By the way, Don and Kyle and the whole AirFlow Performance team are great. Very knowledgeable, always willing to take time to educate their customers, and even helped out giving last ditch ideas to see if a competitors pump could be salvaged. Anyways, Kyle told me that they had re-designed their fuel pump to make it smaller. He sent me the drawings of the pump, and it turns out with some re-arrangement we can fit it in the allotted space.

To do this we are re-locating the fuel filter to the right side, and putting the new fuel pump in the location that used to be the filter and fuel pump. It requires making up some new hard lines to make it all work. The lines are longer and have more bends than the previous setup, but judging by the past fuel flow test, the extra bends shouldn’t be overly restrictive. Greg and I spent the rest of the afternoon working on making the modifications that will make this possible. We made up new hard lines to move the filter. We need to make one more hard line that attaches to the pump, but need the pump to do that accurately. Kevin and I also ran two new wires for the new pump as it draws more current and therefore needed larger wires.

Kyle overnighted me the fuel pump, so I should have it by 0800 tomorrow. I will have enough time (hopefully) to get it installed. If I am lucky I may even be able to do a fuel flow test. But as Murphy’s Law would have it, I was assigned a redeye trip for tomorrow night, so I have to go to work. Sounds like we won’t be starting the engine tomorrow.

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2 thoughts on “All dressed up…

  1. Be sure to:

    Does the new AFP pump have a by-pass and pressure regulation? I know some of those pumps have to have a plumbed fuel return line to a tank to function properly. Careful of that…and possible flow restriction when the pump is not active (mechanical engine driven pump only).


    1. I actually distilled that service instruction into my own checklist for doing that As well as the Lycoming service instruction for the first engine run. I took those two documents and the AirFlow performance and PMag manuals and created a “test card” in checklist format for the first engine run. If you don’t mind looking at it, I will send to you for your comments.

      The AFP pump does have a bypass, though it is external to the pump itself. So in the event the boost pump is inactive or blocked, the bypass will allow flow. That is why it is so much larger than the Andair pump.

      The bypass is actually how the pump regulates pressure as well. There is a relief valve that will circulate back to the pump to regulate pressure. I also just looked at the instructions and it doesn’t require a return to tank. The only thing (to my knowledge) that AFP sells that requires return to tank is their purge valve system.

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