- Jun 3, 2012
Another possibility: If your return line simply empties into the top of the fuel tank air can enter there overnight and the fuel siphons back through the fuel pick up and associated parts. Even though there are usually check valves present they often leak back. If that is the case you can install a pick-up tube fitting on the return line. As a simple test try this: After running the engine, shut off the fuel line at the tank. The next day open that valve and try starting. If it starts right up your problem may be the siphon back described here. Good luck. Please report results.