Initial fuel flow tests - no fuel

I'm scratching my head today. Just tried to do my fuel flow test on my nearly ready 9A. I have a FlyEFII boost pump with pre-filter coming out of my fuel selector. Goes to a firewall mounted Andair gascolator (Canadian requirement) then the engine driven pump followed by a red cube. I disconnected the fuel line at the servo inlet. Problem is that I am getting no fuel whatsoever as far as the open line. Nothing in the gascolator either. The boost pump is running, but makes irregular noises, something between a click and a clunk. I've got a gallon in each tank, same result on both, regardless of the position of my fuel selector. I tried initially at a 15 degree pitch (as is required for fuel flow tests in Canada) and then again after lowering the nose to ~level. I've got no leaks and can sump fuel out of both tanks.

I'm not sure what to look at now. I'll verify the orientation of the boost pump and the pre-filter, but I don't think that's the problem. Is it possible to wire those backwards?

Anyone have any insight? Maybe help identifying the noise I hear?

Thanks.

Sounds like your pump is cavitating/not getting fuel. Try putting 5 gallons in the tank. My DAR wanted a 5 gallon measured fuel flow test. Is this a carb or F/I engine. In general these pumps will need a head of pressure to get an initial "prime", especially the low pressure pumps.

How long are you letting it run for? You have to listen to it make that awful noise for a bit until it draws the fuel in, unless you can prime the fuel lines up to the pump somehow. I recall mine taking at least 5-10 seconds to prime.

Chris

Canadian fuel flow tests are supposed to be done with minimum fuel which is calculated based on engine horsepower. Works out to 1.1 gallons. I can certainly add more fuel to try to get it primed, I'll just need to drain it for the actual test. My engine is an IO-320, Precision Silver Hawk EX fuel injection. My boost pump is a BPM-1. Not sure what's considered a low pressure pump, this one is supposed to deliver 30psi.

With the fuel valve on, and fuel line disconnected at the servo inlet, put a small amount of pressurized air into the vent port to very SLIGHTLY pressurize the tank and wait for the fuel to be pushed through the lines to the disconnnected line. I agree you should probably have more than one gallon in the tanks to start with. Start with 5 gallons.

Bevan.

YellowJacket RV9 said:

How long are you letting it run for? You have to listen to it make that awful noise for a bit until it draws the fuel in, unless you can prime the fuel lines up to the pump somehow. I recall mine taking at least 5-10 seconds to prime.

Chris

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I'm waiting for a good (but not pleasant) 30 seconds on each attempt.

I had the same issue. I assumed the never-got-wet seals weren?t sealing?? Anyway, with the engine side fuel hose disconnected, I just blew thru some tubing connected to the fuel vent until the pump got ?wet?. Then it worked fine. I pumped all the fuel thru and let it sit. Next day it worked okay, no prime needed.

Bevan said:

. . . put a small amount of pressurized air into the vent port to very SLIGHTLY pressurize the tank . . .
Bevan.

Click to expand...

Be VERY careful if you do this as you can very easily over pressure the tanks and damage them. Pressure should be no more than a couple inches of water (e.g. less than 1 psi). I believe a safer approach is to add additional fuel to the tanks instead.

Probably no issue at all, but is your fuel valve set up so that "on" is really on? Be a shame if it wasn't....

Although I imagine that one tank at least would have flowed if this were the case.

Dave

Got it working

Thanks for all of the quick responses on this. I went back out to the airport armed with those suggestions and quickly had fuel flowing. I added more fuel (to 4 gal) to the right tank and blew some air through the vent line to add some pressure. Worked like a charm. Did the same on the left, but probably didn't need to, that one flowed right away. Got my flow tests done with satisfactory results.

Thanks again, I love this place!

Not all fuel pumps are self priming!

Be carefull which fuel pump you are using. Not all fuel pumps that are used in airplanes are self priming!

The Andair fuel pump is and also can work quite a bit of time DRY! But many others do not and get damaged!

Not to think about situations when you got air into the line and the pump is not able to get them out of the system.

Check carefully the specifications, your style of flying and the risk of running a tank dry. Then deceide on which fuel pump you want to install.