Fuel System setup question
Posted: Tue Sep 11, 2012 10:47 am
My fuel system consists of two primary 125-gallon tanks (somewhere around midship) and two 50-gallon "auixiliary" tanks aft. The copper fuel lines from each run to a central manifold with a crossover, so each tank can be isolated, port engine can run off starboard tank(s) and vice versa.
Two weekends ago, while trying to equalize fuel levels in the primary tanks (the starboard was about half full, the port a bit over three quarters full) I had the forward port tank isolated as the only open fuel source with the crossover on, so both engines were running off that single tank. A short time after increasing speed to WOT I lost juice. It took us about 15 minutes of fiddling around with the valves, etc to get fuel flowing again. We pulled a spark arrestor off the port engine and the carb was bone dry; there was no fuel flow.
Captain J thought that the issue was pulling air from the empty port auxiliary tank and flooding the system with air instead of fuel. This explanation seemed sensible at the time because another friend on board started opening/shutting fuel valves, and at that point I wasn't entirely sure of myself as to exactly which tanks were on and which were off. My brother confirmed for me last night that after we got the boat back into port over Labor Day, he isolated that forward port tank to equalize the fuel level (Hart's Desire is listing a bit to port from the extra fuel weight). I thought that was the configuration of the manifold valves when we left port for the ride where we experienced this problem.
My brother's theory was that both of those 440s running at WOT couldn't pull enough fuel through a single line to feed both engines (even though the crossover was clearly open). I thought my broker may have sent me a message similar to this when I advised him of the issue. The engines seemed to run fine at slower speeds - they had been running for about 15 minutes before we came up to speed.
So, is it likely that both engines can't run off a single tank at higher speeds? Or do I have a potential clogging issue on the primary, port tank? The fuel level is dropping, so I don't think that's it. I think I simply learned a lesson about how these engines react to certain valve settings in the fuel system.
Any input would be appreciated. Thanks.
Two weekends ago, while trying to equalize fuel levels in the primary tanks (the starboard was about half full, the port a bit over three quarters full) I had the forward port tank isolated as the only open fuel source with the crossover on, so both engines were running off that single tank. A short time after increasing speed to WOT I lost juice. It took us about 15 minutes of fiddling around with the valves, etc to get fuel flowing again. We pulled a spark arrestor off the port engine and the carb was bone dry; there was no fuel flow.
Captain J thought that the issue was pulling air from the empty port auxiliary tank and flooding the system with air instead of fuel. This explanation seemed sensible at the time because another friend on board started opening/shutting fuel valves, and at that point I wasn't entirely sure of myself as to exactly which tanks were on and which were off. My brother confirmed for me last night that after we got the boat back into port over Labor Day, he isolated that forward port tank to equalize the fuel level (Hart's Desire is listing a bit to port from the extra fuel weight). I thought that was the configuration of the manifold valves when we left port for the ride where we experienced this problem.
My brother's theory was that both of those 440s running at WOT couldn't pull enough fuel through a single line to feed both engines (even though the crossover was clearly open). I thought my broker may have sent me a message similar to this when I advised him of the issue. The engines seemed to run fine at slower speeds - they had been running for about 15 minutes before we came up to speed.
So, is it likely that both engines can't run off a single tank at higher speeds? Or do I have a potential clogging issue on the primary, port tank? The fuel level is dropping, so I don't think that's it. I think I simply learned a lesson about how these engines react to certain valve settings in the fuel system.
Any input would be appreciated. Thanks.