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Touring Motor Gliders Association (TMGA)

Electric Fuel Pump


mikeschumann

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As part of the standard engine start checklist, I test the electric fuel pump..Not only due I listen to see if it is running, but I also wait to see the fuel pressure rise, which used to take about 20-30 seconds. 

Recently it has taken much longer for the fuel pump to prime. During the last couple of flights I gave up waiting for the fuel pressure to come up and just started the engine without the electric pump on.  The engine started normally. 

Does anyone have any ideas on why the electric pump is not priming?  Is this something I should be worried about?

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I rarely watch the pump pressure when testing the electric fuel pump; instead, I watch the fuel flow into the filter near the pump. If the plane has be unused for several days, a lot of fuel flows for a few seconds, then it diminishes to almost zero (I think it's filling the carb bowl, then some is fed from the carbs back to the left tank). As long as the timing and fuel flows seem normal, I'm happy. I do occasionally check the fuel pressure widget on the Skyview. I'm not suggesting this better than checking the fuel pressure, but does give you different information.

So, does your pump put fuel through filter, suggestig the pump is just not producing as much pressure as before? Or is it not putting out any fuel at all, suggesting pump might not have fuel on the inlet, or that the check valve is blocked?

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I'm in the cockpit when I check the fuel pump, so I have no idea what is going on in the filter.  It sounds like a priming issue, or maybe a stuck check valve (or vapor lock).  It's definitely not pumping or there would be pressure.  I can't tell if it is pumping when I turn it on after the engine is running.

Next time I land, I will leave the fuel pump on when I shut down the engine and see what happens with the fuel pressure.

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I check the fuel flow into the filter with the top cowling off, of course, but checking the pressure from the cockpit display like you do sounds like a good additional check. I don't know why I haven't been doing it every flight, instead of sporadically. I don't recall it taking more than 10 seconds to build up pressure, but I will measure it next time I fly.

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This afternoon I left the electric fuel pump on after landing and shutdown the engine. Over 30-60 seconds the fuel pressure slowly dropped to 0. Looks like I need to replace the pump. Does anyone know the part number and a source for the pump?

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  • 2 months later...

I replaced the pump.  The part number was on the component list that came with my motorglider.  Bought the pump on E-Bay for $85 (new).  Solved the problem, so it was definitely a defective fuel pump.  The check valve was OK.

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  • 2 years later...

What pressure are you seeing when/if you check the fuel pressure widget during your preflight? 

What pressure do you see with only the engine driven fuel pump operating either on the ground or in the air?

Trying to compare with the 2 psi that my gauge is reading in either scenario.  rotax-owner.com video says proper range is 2.18 - 7.3

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I turn on the electric fuel pump during preflight.  It usually takes 20-30 to prime before the pressure starts building.

If you look at the specs for this pump, it is not recommended to use it in an application where the pump is above the fuel level in the tank, so priming the pump can be a little challenging.  Once it is primed, the fuel pressure is similar to the engine pump once the motor starts running.

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