Best spot to mount Auxiliary fuel pump KF7

[PNWJARED]

I have a KF7 and am going to install an auxiliary facet fuel pump in line. I know there is plenty of discussion as to add this in series, to add or not to add. I have concluded That i like the redundency and will install it in line. Likely Engine side of the firewall. Though i did want to pull from the vast experience this group has to offer. Mount to the firewall using 90 degree fittings, no fitting before the airbox after the airbox etc...

I am now open to suggestions!

thank you,

Jared

[mr bill]

I did mine in the cabin.

[Dick B in KY]

I placed mine under the center console on my SS7, between the fuel shut off and firewall. Easy to inspect when side panels are off during condition inspection.

Dick B

[PNWJARED]

I see under the seat in parallel. I think the auxiliary fuel pump has a pretty long useful life. So no real need for replacement thus fuel in the cockpit at that time.

I have to change my header tank to the aluminum variety so I will already be working on fuel lines anyway. Good suggestion.

Out of curiosity what is that capacitor for??

[jiott]

Any liquid pump always pushes much better than it sucks, so that would favor mounting it closer to the header tank rather than way forward on the engine side of the firewall.

[Dave S]

Jim Ott is right on - the reason fuel pumps of this type are best mounted in the lowest possible part of the fuel system.

Another point to consider - don't know if this has changed in the current instructions; however, the installation instructions for the fuel pump previously included a statement that the pump should not be exposed to temperatures greater than 140 degrees F.

Sincerely,

[mr bill]

Capacitor eliminates electrical system noise generated by the brushes in the motor. You see the same thing on the alternator.

[PNWJARED]

when we put the fuel pump behind the seat it pressurizes the fuel line from that point on. Pressurized fuel in the cabin? I suspect it is all pros and cons at that point.

[Av8r3400]

Pressurized fuel in the cabin concerned me also.

I plumbed all lines downstream from the auxiliary electric pump with hard aluminum lines for this reason. I only used two short pieces of hose from the tanks to the shut off valves and the header vent line are the only rubber fuel lines in the cabin on my plane.

[n85ae]

That's enough capacitor to function as a backup starter battery ... Probably
the pump runs for 10 minutes after you kick the switch off :)

Jeff


Capacitor eliminates electrical system noise generated by the brushes in the motor. You see the same thing on the alternator.

[Esser]

I don't need to see the need to put the pump further back. Yes, pumps push better than pull but your pump is constantly primed by the gravity head pressure of your high wing tanks. If you mount your pump low on the fire wall the only time it would really have to "suck" fuel is once your header was less than half empty.

[jiott]

Yes but consider this: the only reason you install an auxiliary fuel pump is in case of partial blockages in the fuel lines or filters. Under normal conditions the gravity head alone is enough to feed the engine. If you get a partial blockage in a long suction line (pump mounted far forward) the weak sucking ability of the pump in addition to the restricted and long line probably will not be enough to pump adequate fuel to the engine. Whereas a much shorter suction line may be able to suck adequately even with a partial blockage.

[SWeidemann]

Bringing up the issue of Where & How to install a Aux Fuel Pump?

After taking the Rotax Maintenance course, and talking to Brett at LEAF, I plan to install a Facet electric fuel pump in my KF 5 fuel line (inside the center console after the fuel shutoff).

-May the pump be "hung upside down" from the center console panel?

-Do I need a Capacitor?

-May the pump be "inline" alone, or do I need a bypass valve?

-Do I need a electric shutoff wired to the ignition switch or a oil pressure relay cutoff? May a direct wired pump with a manual panel switch work?

Looking for information and of course, opinions.

Thanks much,

Skot

[Jerrytex]

This kind of ties into a discussion in another thread about fuel flow testing but also ties in with using an auxiliary fuel pump. In the past couple days, I have been working to finish my condition inspection. I decided to do a fuel flow test and noticed that the Facet back up pump does restrict the fuel flow considerably. With gravity only, I was getting 2 gph in a climb attitude and 5 gph in level flight at the inlet to the mechanical pump. (so from tanks to header, through Facet Pump, through shut off valve, through gascolator, to mechanical pump inlet) With the Facet turned on, it obviously shoots a overwhelmingly amount of fuel out. But I guess my thoughts on this are, unless there are bypasses around both pumps, electric and mechanical, I don't think gravity alone would provide adequate flow. Maybe that is why Rotax recommends a back up pump.

[SWeidemann]

Jerry

Your results are what I would expect.

My two preliminary reasons for considering a aux fuel pump was the fact that I replaced the main fuel shutoff valve with a Kitfox Folks supplied generic shutoff valve that had an obviously smaller orifice than the old valve (replaced because the one that came with it turned hard and I felt it was about to get galled and/or stuck) and in my Rotax Service class I discovered that Rotax likes auxiliary fuel pumps in Everything.

In your testing, I would assume the fuel would "slow down" on it's way through all the extra piping of the (non-operating) Facet fuel pump....and of course would pump lots of volume when it was turned on. I'm still going with the pump, I just have to decide if it can be hung by it's heels, whether I need a bypass valve or mount in parallel and if I should have a separate manual switch or hook it up to the ignition switch.

I'm in favor of doing everything I can to make sure this engine gets all the fuel it wants in any phase of flying.

Thanks,

Skot

[airlina]

As I recall, the before that 1st flight fuel flow testing should produce 150 % of max power fuel flow (in GPH or pounds per hour) with the airplane attitude 5 degrees higher than any max attitude in flight. Long ago when I checked mine, I dug a hole on a hill in my yard , put the tailwheel in the hole with the airplane pointed uphill then did my gravity fed fuel flow test. Gave me peace of mind before that first takeoff! Bruce N199CL

[HighWing]

I installed a facet pump on my first Model IV before first flight. It was just after the header tank with aluminum tubing fore and aft to the gascollator. The guy that checked me out in the airplane suggested aux pump on during takeofff. I did thst for a while, then went to straight gravity flow. Until one takeoff after an annual and an over tightened fireshield clamp restricted fuel flow to a trickle. Was able to get about 4000 rpm and returned to the runway. After the fix, it was back to facet off, but comforted by its presence. 900 hours with many in mountain country with nary a hiccup. The switch is a thumb away from the throttle.

[SWeidemann]

Thanks guys for the comments.

Another good thing I found out from Brett at LEAF today is that I can mount my little Facet aux pump cube any way I want to. I interpreted the instructions in the box to mean it should be mounted right side up. It's going upside down under the center console cover in front of the main "on-off" valve.

Skot