Electric fuel pump problem

jfogarty · #1 03-02-2015, 12:38 PM

Electric fuel pump question and problem, my plane has not been started for over a month and the boost pump doesn't seem to be bring fuel to the carburetor. I have had this happen a number of time this winter, however, it will usually start. Today it was a no go, any ideas? I don't have an engine primer.

0320 E2A, 150 hp. RV-9A, 51 hours, warm hangar, 2 below today. Standard Vans electric fuel pump.

Jim Fogarty
RV-9A, flying

krw5927 · #2 03-02-2015, 02:18 PM

This is rather frightening. Are you saying the Facet cube pump turns on and you can hear it clicking away, but fuel pressure stays at zero?

What happens when you turn the fuel selector to the other tank? Is there perhaps some obstruction in your fuel line from one tank?

The reason it's frightening is that in flight, if your accessory case-mounted pump fails, you don't exactly have what one would call a dependable backup. On the off chance this happened close to the ground, or even forced an off-field landing, results could be catastrophic.

The electric pump isn't just for starting....

jfogarty · #3 03-02-2015, 02:46 PM

The fuel pump just clicks away, with no smell of fuel and the engine will not fire. I believe no fuel is being delivered to the carb. I didn't look at the fuel pressure, I will look at that later today. The Skyview was not up and running prior to trying to start today. Also, I can blow into the vent lines and hear no air from the left or right tank. Both vent lines seem plugged. In the Cessna high wing I can always hear air going into the tank.

Jim Fogarty
RV-9A flying

Mike S · #4 03-02-2015, 02:55 PM

Quote:

Originally Posted by jfogarty

I can blow into the vent lines and hear no air from the left or right tank. Both vent lines seem plugged.

This is not good.........................

Try removing the fuel cap, and see if the pump will move gas that way.

I have a piece of fuel hose that fits over the vent stub, about 6' long, I slip it on the vent stub, and lean over the open fuel filler and blow in the hose. If there is any air motion, I can hear it.

Also, if the vent is plugged, you will feel back pressure when you blow in the hose.

guccidude1 · #5 03-02-2015, 08:31 PM

I might have the solution. I have seen this on another low wing aircraft with the Facet pump. The problem was that the builder had a fuel filter, located under each seat pan, on each tank line to fuel selector. There was more air trapped in the filter than the Facet pump could suck out to get the filter fill with fuel. The filters were clear plastic and you see the fuel in the filter, when selected, move forward and back. Smaller filters with less air space solved the problem. Unregard if you don't have this filter setup. Dan

gasman · #6 03-02-2015, 08:49 PM

Quote:

Originally Posted by jfogarty

The fuel pump just clicks away, with no smell of fuel and the engine will not fire. I believe no fuel is being delivered to the carb. I didn't look at the fuel pressure, I will look at that later today. The Skyview was not up and running prior to trying to start today. Also, I can blow into the vent lines and hear no air from the left or right tank. Both vent lines seem plugged. In the Cessna high wing I can always hear air going into the tank.

Jim Fogarty
RV-9A flying

Defiantly the first step..... But even without the electric boost pump working, the motor should start with only the main fuel pump working.

To start, the motor needs 3 things..... fuel, air and ignition. Proper air/fuel mixture sure makes it easier.

jfogarty · #7 03-03-2015, 10:18 AM

Okay guys thanks, I will let you know the outcome. I did remove the fuel caps and ran the booster pump yesterday before giving it a last try. Also, switched tanks from left to right. I'm going to try the 6 feet hose trick next. Over the last 6 months as soon as I get fuel to the carb it will start. Thanks.

Jim

az_gila · #8 03-03-2015, 11:46 AM

Look for an air leak or a loose fitting upstream from the pump.

krw5927 · #9 03-03-2015, 11:50 AM

Quote:

Originally Posted by jfogarty

Okay guys thanks, I will let you know the outcome. I did remove the fuel caps and ran the booster pump yesterday before giving it a last try. Also, switched tanks from left to right. I'm going to try the 6 feet hose trick next. Over the last 6 months as soon as I get fuel to the carb it will start. Thanks.

Jim

If you tried the pump without the fuel caps on, then that eliminates the possibility of blocked vents causing the issue. Might as well skip the hose trick, unless you just want to verify they're not blocked. You still have a problem though.

Also, since you switched tanks and still had the problem, it's not an obstruction in the lines from the tanks. My money is on either a bad pump or a pump that is sucking air due to a selector problem or a loose or bad fitting between the selector and pump.

If there is positive fuel pressure of 3-5 PSI when you run the pump, but the engine doesn't start, that's a different issue all together. Knowing whether the pump is making pressure is key here.

Either way, even if you are able to get the engine running, please do not fly until you get to the root of this issue. This is a real safety of flight concern.

Ralph Inkster · #10 03-03-2015, 03:18 PM

Sure it's a fuel delivery problem? Aux fuel pump only aids the mechanical pump in delivering fuel to the carb, by rights the mechanical pump should be able to start the engine- even without the aux pump on.

Lycomings need a fairly rich air/fuel mixture to start in cold weather & without a priming system may be very hard to if not impossible. If you have an accelerator pump on your model carb, you could try pumping the throttle knob in & out rapidly while turning over the starter, this might produce a rich enough mixture to fire the engine, though most o-320 carbs don't have accelerator pumps. Only do the throttle pumping trick while turning over the engine otherwise you are just dripping fuel into your air cleaner. To know if you are actually pumping fuel with the accelerator pump, smell in the aircleaner area for strong smell of fuel, caution if too flooded and the potential of an induction fire.

Back to the aux pump testing, note that most fuel lines retain some amount of pressure after engine stop & pressure you read on your monitor may be this residual pressure. The ultimate test for aux fuel pump flow is disconnect fuel line at carb & place a bucket under it, when aux pump on you should see well over 14 gal/hr flow thru the line.

Good luck