I have finally overcome my paralysis and went back to the hangar to take the fuel system apart in my hunt for the bug that causes gas to just drizzle slowly out of the gascolator (when the bowl is removed).
By disconnecting the pushrods for the flaperons in the back where they are attached to the control horns, I was able to push them outboards just enough to allow a wrench to unscrew the nuts on the fuel pump fittings.
Once the lines were unhooked from the pump I was using a PVC hose to attach to the lines and blow some air through it (careful with the line between tank and pump! Remove the cap before doing this so to not inflate the tank). Both lines were free of any noticeable restrictions. The forward line was a little less open but I could hear the hissing, turbine-like sound of the flow transducer as the air was rushing through, so I am sure I got great flow.
I want to order some more fittings to confirm that it is indeed the pump that is causing the slow flow and not the tank before I go about removing the pump. Also, I want to be able to confirm that the replacement pump is indeed working better than what I have in the fuselage right now.
Maybe a very dumb question- but is the tank vented to allow fuel to flow freely? Vent line clogged or kinked perhaps. Just a guess on my part- not that far into the project myself.
ReplyDeleteAnother suggestion- is this a gravity feed fuel system, or do you have a fuel pump. Could you disconnect the fuel line from the engine, turn on the fuel pump and measure flow rate?
Just guesses- probably frustrating... but thought I'd throw out some suggestions.
Good luck
The RV-12 version I am building (yours will be different and much better for the venting) has a modified fuel cap that ensures venting. I had removed the cap though during the test to exclude a problem with it. The RV-12 has an electric fuel pump after the tank that primes the system when the engine is not running (the engine provides its own mechanical fuel pump. Either pump alone should be sufficient to keep the engine running). There is a fuel flow rate meter in the line as well but to avoid calibration issues, the test is time based and done with the engine disconnected (draining into a bucket with an open gascolator bowl).
DeleteThe pump definitely had a problem. If it was the main cause for the slow flow I do not know yet but I am at least one step closer to solving it.