Brief Description: Troubleshooting Fuel Pumps High Current Draw
Troubleshooting Fuel Pumps High Current Draw that only became evident with the use of the auxillary fuel pump that is wired to the Vertical Power System. The VP dispaly showed tha the pump was drawing close to 12 amps when it should have been around 6-7 amps. Up to this time, the engine seemed to run well and I was not familiar with the sound of the pumps to be able to say tah they were laboring. I deduced that the pumps were laboring either because of the pumps were failing or that there was a restriction downstream. I disconnected the fuel return line just after the fuel pressure regular as a start point. I connected a clear polyprop tube to the line and drained it into the fuel supply tank. What I noticed was that the pumps still sounded labored and the current draw was still high. I also noticed air in the line. The question was now whether the pumps were cavitating and thus labored. I tightened the fittings but did not see any significant change in the amount of air. I used a clear tube as the supply tube from the fuel tank to the Andair Selector Valve. No air in the supply line but air was present in the return line. Decided to try supplying fuel from the right side of the aircraft. Surprise! The labored pump sounds ceased and the fuel pressure increased from 35 to 42 psi. I thought the source of the problem was the fuel selector since that was the only common element. Further investigation needed.
