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  #1  
Old 11-11-2005, 11:28 PM
Steve parkins's Avatar
Steve parkins Steve parkins is offline
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Location: wa state
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YOU GOT 10 ON ONE,,,,,100 ON ONE
YOU CLEAN BOTH
YOU NOW HAVE 90 ON ONE,,,,110 ON THE OTHER
SOUNDS LIKE FINE DIRT, FUZZ I CALL IT.
TO SMALL TO SEE, I SEE IT ALL THE TIME IN RACING CARBS
MY THOUGHT IS CLEAN EVERY TWO RACE

but in your case, I'd set up a test bed that could be hooked up to the pumps
easy with out removing them from the plane

lets see, hot wire from battery not on plane
gal can with new fuel and a small lead to pump
small lead away from pump going to a carb jet(just a small hole in the fuel line)
and a gage fit in the line to read the pressure
be for fight hook up left pump,spray 1 min(read pressure)
then do the same for the right pump(read pressure)
lets say you do it now that you just cleaned them and you get 72 pds and 68
as long as they stay clean you should get that the next time you test.
but heres my point,the next time they ack up dont clean but test and if you get 20 and 60 you mite look at the fuel,but then clean and retest

get a glass test tube fill and let stand for 12 hour,your fuel and some from the gas station and see if they look the same
  #2  
Old 11-11-2005, 11:40 PM
John Slade's Avatar
John Slade John Slade is offline
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You wanna now what's amazing...

I completely understood all of that.
  #3  
Old 11-12-2005, 12:21 PM
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rv6ejguy rv6ejguy is offline
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I'd go along with MP on this one. You need to perform a volume @ pressure test as the pressure itself is rather meaningless without knowing volume. Easiest way is to disconnect the return hose from the reg, fire up the pumps and measure the volume of fuel put out in 1 minute. This will force the pumps to put out reg pressure. You should see a minimum of 2L/ 2QT per minute in this test and both pumps should be very close or you have a problem with them on a line or filter restriction. As a further test, apply regulated shop air to the manifold reference port on the reg, say 10 psi. Fuel pressure to go up 10 psi and pump volume will decrease slightly, just make sure you still have the volume required to feed the engine.

If you have proper filters before each pump, you should never have a problem with crud in the pumps, only crud in the filters. A simple mouth blow test through the filters can usually verify condition. If you turn blue in 5 seconds, the filter is bad, if you can blow easily, it's likely ok.

Again, I've seen more than a few EFI pumps pass the pressure test, pass a free stream volume test but flunk the combined test. If fuel pressure falls off at WOT and high rpm on the runup, don't fly.

Just had a similar problem this year on my Nissan 240SX turbo. Intermittent lean out at WOT. Sometimes ok, sometimes not. Taped a fuel pressure gauge to the windshield and drove it under boost. Sure enough, fuel pressure would sometimes start to fall above 4000 rpm and it would lean out. Fuel pressure was always fine at idle where no volume is demanded. New Walbro pump cured it and it storms like it used too again.

Checking connections is also a great idea and current draw if you can. Eliminate everything before you fly again.
 


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