New fuel pump
in 912 / 914 Technical Questions
14 years ago
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by bill martin » 12 years ago
Ken,
If I understand your plumbing, you are pumping fuel into the gascolator with the Facet. If your return goes into the Gascolator, the return line is trying to return fuel into a pressurized gascolator while the Facet is on. That won't work well. It would work OK with the Facet off but may not work so well with the Facet on. The Facet does definitely act as a check valve and would prevent any pressure relief when the engine is turned off. You might try a tee immediately behind the Facet on the suction side and plumb the return to that. This would allow the fuel to return to whichever tank is in use. No need for another valve.
Hundreds of planes are running without return lines with no problems. They are mainly useful in enclosed, tight, hot cowlings to prevent vapor lock.
Bill.
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by bill martin » 12 years ago
Ken,
I forgot to ask. Are you using a restrictor in the return line? If not, you will have very little pressure in the fuel lines going to the carbs.
Bill.
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by Ken kitzmann » 12 years ago
No I never had a restrictor, where would you get one, in the Rotax manual it does not show anything about a restrictor. If you read my last post again it would only run with the electric boost pump running, once I shut off the electric boost pump it would sputter within a minute @ 5400 rpm. I have run 140 hrs without a return line, but thought having a return line would eliminate over pressuring of the diaphragms of the mechanical pump??? as I had one pump start to weep.
I only use the facet on takeoff and landing, otherwise the mechanical pump sucks from the strut mounted tanks only which are basically the same height as the mechanical fuel pump or actually even lower.
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by Ken kitzmann » 12 years ago
I have no cowling, and use some fire sleeve in areas of heat and abrasion.
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by Ken kitzmann » 12 years ago
In Roger Lee's post # 2200 he says one could use a bing jet as a restrictor in a return line...how would one secure this in the line ??? with a clamp on outside ??? or just put it near a juntion and it would but up against a barbed nipple ???
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