celstar

celstar

Well Known Member
Did my run up today and seen 0 fuel pressure at 1800 rpm! I have a Aerosport O 360 Carb not injected. The plane seems to run o.k at this rpm however when i bring it down to 800-900 it seems to miss a lttle witch i believe to be fuel related. The motor does not totaly stop it still keeps runing and when i turn on the fuel pump the pressure goes up to around 5-6 pounds. I turn off the boost pump and it slowly comes down to zero. Any ideas would be great, Im thinking mechanical fuel pump but dont know why this would be out at only 90 hours tt?
 
celstar said:
Did my run up today and seen 0 fuel pressure at 1800 rpm! I have a Aerosport O 360 Carb not injected. The plane seems to run o.k at this rpm however when i bring it down to 800-900 it seems to miss a lttle witch i believe to be fuel related. The motor does not totaly stop it still keeps runing and when i turn on the fuel pump the pressure goes up to around 5-6 pounds. I turn off the boost pump and it slowly comes down to zero. Any ideas would be great, Im thinking mechanical fuel pump but dont know why this would be out at only 90 hours tt?
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possible, infant mortality.
 
What?

Just curious how it could even run with 0 fuel pressure. My guess is that your fuel-pressure indicator is wrong.
 
It is not uncommon to see fuel pressures vary and go down to zero. You may be flying along or on climb out and the fuel pressure drops to zero with the engine running just fine. I spoke to Bart about this several planes ago and said it was a common occurence. He had no real answer for it. I did notice that when the boost pump was turned on sometimes the pressure would increase sometimes by a pound or two. But in your case you say the pressure is dropping with the boost pump on. Check your fuel pressure with the engine off and the boost pump on and check for leaks. Check both tanks, maybe a leak on the input side causing air to enter the system but I doubt it. Srange.
 
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But in your case you say the pressure is dropping with the boost pump on.



The pressure goes up and stays up when the boost pump is on, when i turn off thr boost pump it will slowly go back down to zero with the engine running.:mad:
 
Sounds like your mechanical pump is dead or dying. There may be just enough fuel flow (that doesn't registered on the gage) to keep the engine running. Because the boost pump get the pressure readings up, I'd replace the mechanical pump right now.

Have you flown it like this? What was the result?
 
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I know this is VERY basic, but you are sure the pressure line is downstream of the mechanical FP and not off the inlet? Also bleed any air out of the line to the transducer. Infant mortality would be probable if the plumbing is right.

Bob Kelly
 
Geico266 said:
Sounds like your mechanical pump is dead or dying. There may be just enough fuel flow (that doesn't registered on the gage) to keep the engine running. Because the boost pump get the pressure readings up, I'd replace the mechanical pump right now.

Have you flown it like this? What was the result?
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I have not flown it like this, I do not want to untill i see somthing for fuel pressure with out the boost pump on.
 
celstar said:
I have not flown it like this, I do not want to untill i see somthing for fuel pressure with out the boost pump on.
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To paraphrase Bob Kelly, where is the pressure sensor installed? The evidence is the sensor is ok but installed between the boost pump and the engine pump.
 
videobobk said:
I know this is VERY basic, but you are sure the pressure line is downstream of the mechanical FP and not off the inlet? Also bleed any air out of the line to the transducer. Infant mortality would be probable if the plumbing is right.

Bob Kelly
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I will check this all out today. The plane now has around 100 hours on it and has all been great up until now. I just recently replaced my Tru Track auto pilot because of a bad gyro and also sealed up my plenum area with more rtv for better cooling oh, and also replaced my air cleaner with a new one. I can not think of anything that would have caused this from these items?
 
If you still aren't getting pressure, look at your boost pump too. I had a -6 with the little square Facet pump that had a partial blockage, which caused similar symptoms to those you describe.
 
Thanks all

Thank you to everyone that helped with this. It turns out that it was a stuck Gascolator drain. When i did the last engine area check and changed the air cleaner i drained some fuel from the gascolator, It stuck open!:eek:
 
Change that drain!!!

celstar said:
Thank you to everyone that helped with this. It turns out that it was a stuck Gascolator drain. When i did the last engine area check and changed the air cleaner i drained some fuel from the gascolator, It stuck open!:eek:
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If your gascolator has the type of drain that can be turned and locked in the open position, I strongly encourage you to replace it with one that does not lock open. There is no useful application for the locking one on a gascolator and it can cause an accident. Some where around 1990, one of the first completed RV-6's with only a few phase one test hours on it, crashed on takeoff because of this very problem (ran fine at full power for about 10 seconds).
 
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