January 31

Today I replaced the auxiliary fuel feed pump for the generator. The aux. fuel pump was originally installed to function as a bleed, or priming pump. It was installed in a bypass loop with 3 valves to control when the pump is in the circuit so it can be cut out of the circuit during normal operation. When the pump is in the circuit, a momentary switch is used to prime the racor fuel filter and the engine further downstream.

In San Diego we figured out that the genset wasn't getting enough fuel. It is because the height of the highest point in the run is too far above the fuel tanks for the puny little lift pump on the genset to pull the fuel uphill. Apparently these pumps are designed for pushing fuel not pulling. The solution seemed simple at the time - leave the bleed pump in the circuit during generator operation and re-wire the switch so the pump is always on (when the pump breaker is on). So I bypassed the switch and it seemed to work. For a while.

Eventually we burned out the bleed pump and it stopped working. I have several theories, but the truth may not come till I take the old pump apart and see what is wrong. My best guess is the pressure relief switch is busted and stuck in the off position.

Instead of replacing the pump where it was, I tried to improve the situation by removing the bypass loop from the circuit and plumbing the new pump (henceforth known as the Aux. Feed Pump) directly inline between the pickup from the fuel delivery manifold to the racor fuel filter. This way the pump should not have to work as hard pulling the fuel around the loop (a photo in the January Photo Gallery shows the new setup and the remains of the old bypass loop).

I took about 5 hours to complete the plumbing surgery, part of which was spent shortening a piece of over-sized hydraulic hose used as fuel line. In the end, I had to use a circular saw to cut this stuff (steel braiding is sandwiched between and inner tube and outer covering). We ran the genset under moderate load conditions yesterday for 2 hours and it performed fine. However, subsequent tests of longer duration will be required to fully prove the systems is stable.