AFP boost pump not pumping

erich weaver · #1 11-23-2007, 07:19 PM

I am trying to work toward a first engine start this weekend and at the end of the day today I checked to see if my AFP boost pump would actually pump fuel. I had 10 gallons in my left tank, fuel valve set to left tank, and I disconnected the fuel line that goes from the engine driven fuel pump to the fuel pressure transducer and directed it into a gas can after removing the restrictor fitting. Turned the switch and heard the pump humming, but no fuel came out after 20-30 seconds.

I didnt have time to troubleshoot much, but Im pretty sure I have everything plumbed right. Does the pump need to be primed somehow to get it going or am I missing something else?

thanks

erich

AlexPeterson · #2 11-23-2007, 08:05 PM

Erich,

It should not take that long. The output of those pumps is about a half gallon per minute, albeit a little less coming from your smaller pressure line. If you have 10 gallons in a tank, it should essentially self prime due to gravity - the pump will be below the fuel in the tank. The lines don't hold that much fuel, so 20 to 30 seconds is a lot of fuel.

It certainly is easy to get confused on those boost pumps and their associated valving, perhaps you could post a picture of the setup?

Exciting times - first engine starts!

Ron Lee · #3 11-23-2007, 08:14 PM

Priming may have been the solution.

Adam · #4 11-23-2007, 09:15 PM

I had the same problem, the pump just needs a one time prime, that should fix it.

Martin Sutter · #5 11-23-2007, 09:48 PM

Confessions of an oldtimer

The same thing happened to me. After taking everything apart and re-checking the fuel would still not flow. In desperation I decided to lightly pressurize the tank. Soon the fuel started to flow even before I turned the pump on but to my surprise it stopped when the pump started running! More head scratching..... Finally I had a hunch....could the pump be running backwards??? Yep, you guessed it, I had the polarity reversed. I only discovered that when I checked with the volt meter because the wires were labeled incorrectly so it passed my previous check. Lesson learned - Never assume anything!!!

Martin Sutter
building and flying RV's since 1988

erich weaver · #6 11-23-2007, 10:10 PM

I'll double check electrical polarity and plumbing tomorrow. A light pressurization of the tank sounds like a good way to prime the pump, but not sure how Im going to achieve that yet. Hmmm... maybe blow up a balloon and stick it on the vent line fitting, or just blow through a piece of tubing I guess.

I'll report back tomorrow, hopefully with a success story.

erich

RV7Guy · #7 11-24-2007, 09:54 AM

You didn't say which fuel valve you have. I have the stock Van's valve. On first engine run I had the little pointer on the tank instead of the big end. As soon as I switched it the pump grabbed the fuel fine. I pulled the selector handle and ground off the little pointer.

Try cycling the valve through to see if it will pull fuel. Also noted, check polarity.

Good luck. Let us know what you find.

erich weaver · #8 11-25-2007, 05:55 PM

All ok now. Worried over this for two days but problem solved 30 seconds after arriving at the hangar to troubleshoot. I simply turned on the pump again and swiveled the fuel lever around a full 360. Out came the fuel in a nice steady stream. Not exactly sure exactly why this worked - probably broke an airlock somehow.

I am curious about what Darwin said on the previous post - that he didnt get fuel flow because he had inadvertantly had his lever pointed 180 degrees off the mark since he used the pointer instead of the handle of the standard fuel lever. I was under the impression it wouldnt make any difference - as long as the handle (and pointer) are in alignment with the valve it will pass fuel. I havent investigated this yet to confirm though.

Anyway, all is now right in the RV world - see my other "first start" post.

thanks for the tips guys

erich

#9 11-25-2007, 06:11 PM

Quote:

Originally Posted by erich weaver

I am trying to work toward a first engine start this weekend and at the end of the day today I checked to see if my AFP boost pump would actually pump fuel. I had 10 gallons in my left tank, fuel valve set to left tank, and I disconnected the fuel line that goes from the engine driven fuel pump to the fuel pressure transducer and directed it into a gas can after removing the restrictor fitting. Turned the switch and heard the pump humming, but no fuel came out after 20-30 seconds.

I didnt have time to troubleshoot much, but Im pretty sure I have everything plumbed right. Does the pump need to be primed somehow to get it going or am I missing something else?

thanks

erich

My AFP pump got dried out after sitting on the shelf for 3 years. After pouring some gas through it, it worked fine. See this thread about that issue: http://www.vansairforce.com/communit...37020#poststop

-Geoff

RV7Guy · #10 11-25-2007, 09:37 PM

Quote:

Originally Posted by erich weaver

All
I am curious about what Darwin said on the previous post - that he didnt get fuel flow because he had inadvertantly had his lever pointed 180 degrees off the mark since he used the pointer instead of the handle of the standard fuel lever. I was under the impression it wouldnt make any difference - as long as the handle (and pointer) are in alignment with the valve it will pass fuel. I havent investigated this yet to confirm though.

erich

Hi Erich,

Don't really know. I do know when the little pointy thingy was aimed at the L or R it didn't work. As soon as we pointed the paddle at the L/R the fuel flowed. I haven't tried it the other way again. No need to.

Glad that worked and you got the prop to turn!!!