Online Community of Zenith Builders and Flyers
Something I've noticed...
Before each flight I run the engine on both pumps to make sure they both work. I haven't yet switched over to the back-up pump in flight, but after landing on the taxi in, if I switch to the backup pump, the engine quits.
The pump works, but there must be air in the line I'm guessing. It's not there before flight, but after something must be holding up the fuel.
When I restart the engine, I can switch between pump 1 and 2 all day long with no issue. It's just that initial switch after landing.
The ability to run both pumps on take off and landing was the single biggest reason I switched the pumps separately, not that that may have to be standard practice but I just like having the capability if so desired.
Agreed on wether it’s an actual problem either way. Just a good thing to be aware of and proceduralize.
I have not done the 2019-2 SB and I don't think it is necessary for me as I have a header tank and can only think of a couple of ways how it would "unport" the fuel supply which are avoidable. I have switched pumps in flight with no observable issues. I recently had the Circuit Breaker on my main pump trip during climb-out and I immediately switched to the aux pump and the engine restarted without me turning the key.
I finally received my parts to do the SB, but I'm no longer having this issue. Some may remember that I had an issue with a few of the banjo fittings on the final fuel filter and the fuel pumps leaking. I removed the pumps, annealed my copper washers, and rebuilt it and I no longer seem to have the issue with the engine quitting when changing pumps. Not sure if rebuilding had any affect, but either way I haven't had the issue since.
I'll prob still do the service bulletin though since I have the parts even though I don' think the new part that UL Power wants the owners to swap has any affect on the issue of the engine quitting. The problem is losing fuel pressure during the pump switch.
I'd bet you had a little air in leakage on the standby pump, through a crush washer. Where I worked, this was not uncommon after pump rebuilds with new gaskets/washers. Not enough air to affect operation but enough to get a bubble in the non running pump circuit.
Good to hear it worked out.