Replies to This Discussion

Permalink Reply by Loren Warner on February 16, 2020 at 8:24pm

Vent the fuel line at furthest point possible beyond fuel pump(s), and with engine starter engaged.

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Permalink Reply by Loren Warner on February 16, 2020 at 8:29pm

I don't recall if your engine is carbureted of fuel injected, but try loosening the fuel line fittings at the carb or injectors, wrap with rags and turn over engine to pump fuel.

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Permalink Reply by David J. Beaulieu on February 16, 2020 at 8:43pm

Mark, first...leave everything connected and run your fuel pumps.  Fuel won't go any further until you run the pumps. This should circulate the fuel through the entire fuel circuit.  If it doesn't,  listen to hear if your pumps are "loaded" or just cavitating.  You should not have to turn your starter to get fuel to flow.  The pumps should run independent of RPM even with the fuel pump shutoff relay wired (at least for about 15 secs)  Get back to us with what happens.

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Permalink Reply by Mark Pensenstadler on February 16, 2020 at 9:22pm

David,

What you described is what I initially did. With everything connected, I turned on the master switch and pump 1 ran for about 15 seconds. It never sounded like it was under load and I don't believe it was pumping any fuel. After it turned off, I ran pump 2 and it didn't sound like it was pumping any fuel either. 

That is when I disconnected the hose so I could see if fuel was making it past the gascolator (it is). So it seems the fuel is getting all the way to at least the bottom of the two little fuel filters but not making it up to the pump. That's were I'm stumped!

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Permalink Reply by Robert Riat on February 16, 2020 at 9:33pm

When I first ran my pumps, I didn’t have the pressure hose connected at the engine, but rather had it

in a container to retrieve the fuel and check for flow.  I ran both pumps, independent of each other until

I had checked to make sure they were delivering proper volume.  I didn’t start the engine for a few 

weeks after that and it then started instantly after the main pump ran a few seconds and built pressure.
The fuel system has worked really well for me, so far.  Sounds like you just have air building pressure

and holding back the pumps. D5D77A7F-F45D-4F69-B42C-E021423C1310.jpeg

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Permalink Reply by Perry Hyden on February 16, 2020 at 9:04pm

Mark,  I just did my fuel flow test last week.  I measured the flow at the hose you have removed.  For some reason I have in my mind that fuel will not flow through the pumps if they are not running.  May be wrong.  The UL Power install guide says to measure fuel flow at the return line with the pump running.

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Permalink Reply by Mark Pensenstadler on February 16, 2020 at 11:05pm

Thanks Perry, I would agree with you. I don' think the fuel fill flow through the pumps if they are not on. So I will do the same and disconnect the return line at the firewall and do the flow test from there with the pump running.

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Permalink Reply by Loren Warner on February 16, 2020 at 9:20pm

I'm glad others chimed in, I wasn't sure what fuel pumps you had, just sounded like a vent problem to me.

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Permalink Reply by Mark Pensenstadler on February 16, 2020 at 11:01pm

I have fuel flow and pressure! I'll tell you what I did, but first let me back up a little. I also thought that maybe there was an airblock somewhere so I disconnected the hose from the downstream side of the final fuel filter (see pic). Then I ran the pumps and....nothing. I couldn't even feel air pumping out of the opening. Neither pump was pumping fuel.

Earlier in the day I was adding fuel and calibrating the fuel senders in the Dynon so I had ship power on a lot today. 

So just now I was trying different things and running the pumps and I noticed my battery voltage was 11.3 (or maybe it was 11.6 I don't remember exactly). 

So I connected the battery charger to the battery and then decided to try the pump again. Within about 2 seconds I heard that sweet sound we all know of the pump changing from a high whine to grumble. It was pumping fuel. I also could tell because I had a geyser of fuel coming out of the final fuel filter because the hose was disconnected! 

So I let it run for the 15 seconds and when the ECU shut off the pump, I ran pump 2 and the same thing-it went from a high pitched whine to the low grumble. It pumped the fuel and I believe I could hear it returng to the tank. Yes, I had reconnected the hose.

That's all I did to make it work. Maybe less than 12 volts isn't enough voltage for the pumps to spin fast enough to actually suck fuel? That's kind of worrisome. Or, maybe now that the entire system has fuel in it the pumps don't have to work as hard and if the voltage ever drops to 11.6 or 11.3 in flight it would still be enough to operate the pumps?

So it's all fixed. I'm hoping for some nice weather tomorrow and I'll tie the plane down (still no brakes) and I want to run the engine. 

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Permalink Reply by Greg Booker on November 24, 2020 at 1:41pm

Had the same thing happen. Had to laugh. The Pumps were blowing instead of sucking. Changed + to -   All better.

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