Testing a Yamaha F115 for suspected fuel injection pump failure. This is one of the most common running issues we encounter with 4 stroke EFI. Motor will run normal at idle and through mid range throttle but falls on its face approaching wide open throttle and the VST pump fails to keep up with demand. Normally the motor won't completely stall, but stalling can occur. We are measuring fuel pressure at the injector rail using our FST Fuel Pressure Test Adapter Kit connected to the Schrader fitting on top of the rail with Hose Extension connected to a standard automotive fuel pressure gauge to test fuel pressure in open water. Fuel Injection and VST (Vapor Separator Tank) Pumps can be notoriously tricky to diagnose in the shop and will often turn normal fuel pressure during testing until the pump is tested with the boat in open water and full demand is placed on the pump to maintain fuel pressure to spec (38 to 40 PSI) at higher volumes demanded by the ECU to turn full RPM's. This motor had normal fuel pressure at all RPM's in the shop, but in the river lost fuel pressure as soon as I went near wide open throttle. Confirmation of either a failing VST High Pressure Pump or an obstructed pump or both. The result is the same: back to the shop for a fuel system tear down.
[ Ссылка ]
