Electric Fuel Pump procedure

Getting close to first flights in my Javron Cub, it is fuel injected and I cant seem to find anything definitive about when to operate the electric fuel pump. My thoughts are that I should operate it for takeoff and landing if the engine runs well with it on, in lieu of any other guidance.

Does anyone have any references or recommendations?

Specs:
IO-375
Standard 3/8” fuel line
Airflow performance electric pump
Silverhawk FI
No Gascolator
9:1 compressions
Superior cold air induction (horizontal induction)
Trailblazer prop
Slats (possible high deck angle on climb)



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All airplanes should have a Gascolator to catch and separate any last ditch contaminates and water.

It's always advisable to run an aux fuel pump on fuel injected engines in case of engine driven fuel pump failure on take off or landing. This is just to eliminate one thing for the pilot to think and do if needed when in close proximity to the ground. A hiccup can distract. Just remember to turn it off when not needed if only to reduce the time on the pump. Sometimes a power on warning light will help you remember to turn it off.

If the engine driven pump never fails, then you didn't need to do this. But what if it does?

The aux pump is also used for priming the engine before starting.

Thanks for the input! I left the gascolator off at the recommendation of airflow performance since their filter setup includes a filter. The low point or sump area is on the bottom of my fuselage/boot cowl just prior to the filter and electric pump on the firewall. Im well past the good idea cutoff line on this one so hopefully it works out and I dont have to install one later.

Ive heard that running the pump can cause the engine to run rough on some planes, is this just confusing carbureted planes with boost pumps vs injected? I know that some carbureted planes with bigger engines didnt have large enough fuel lines and the way around not replumbing the whole fuel system was to install a pump that is typically not used for takeoff though. Like a c-170 with a O-360 comes to mind. Isnt a 185 the same? Even though injected the pump is off for takeoff?


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supercub83a said:

Ive heard that running the pump can cause the engine to run rough on some planes, is this just confusing carbureted planes with boost pumps vs injected?

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Electric aux pump on for takeoff and landing in my FX-3. Also used for cold start prime. Lycoming YIO-360 (CC 363i) with Avstar servo mounted horizontally. There is an increase in fuel pressure with the electric pump running but I have not noticed any change in fuel flow.

supercub83a said:

Ive heard that running the pump can cause the engine to run rough on some planes, is this just confusing carbureted planes with boost pumps vs injected? I know that some carbureted planes with bigger engines didnt have large enough fuel lines and the way around not replumbing the whole fuel system was to install a pump that is typically not used for takeoff though. Like a c-170 with a O-360 comes to mind. Isnt a 185 the same? Even though injected the pump is off for takeoff?

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We'd need to know more details of this to make a judgement. If the aux pump's output pressure exceeds the engine driven pump's, it could be possible to have too rich a mixture. Generally an aux pump is more critical with a low wing airplane than a high wing, and that being with a carburetor. The modified airplanes which you mention use an aux fuel pump to ensure adequate flow with the small fuel lines. Without the pump the small lines would not flow enough fuel.

The 185 has a two speed aux pump which is normally only used for starting and emergencies. One time I forgot to turn it off after starting. During take off it ran rough when the high speed position kicked in. There is a micro switch on the throttle which turns on the high mode.

I have an aux pump in my fuel injected 180 hp Cub. The engine driven pump is a gear pump rather than a diaphragm pump. I usually do not run the pump on take off and landings. I have run it, with no noticeable differences. It's easy to forget to turn it off, particularly since you can't hear it running when you're flying. On hot days with a hot engine, it is a good idea to run the aux pump on the ground to prevent the engine from stopping. It has a tendency to develop air in the injection lines causing poor running under those heat conditions.

If you do decide to run the aux pump on all your take offs, install a "pump on" warning light as a reminder.

I have API injection and omitted the filter and used a Steve’ gascolator instead.

We’re advised to run the electric pump for takeoff and landing but I rarely have. Not by design. In fact I added a fuel pump indicator light to remind me.

I can’t imagine the pump making your engine run rough. It sure shouldn’t. I can leave mine on continuously if I choose. A friend has no mechanical pump so uses dual electric pumps. One primary, one backup. It works fine.

Mooney and Decathlon procedure is to run it on takeoff. Instead, I just pre-brief before each takeoff - “if it quits, turn this switch on.”

pump lasts longer that way.

As to the mechanical pump failing - it is usually a diaphragm that fails, and I am not convinced the electric pump can run fast enough to feed the leak and the engine. I will turn it on anyway, and off hopefully before impact.