Has EFI with MPI and a VST system (not a cooler)<br /><br />So far:<br /><br />Changed plugs, wires, cap and rotor<br />Changed fuel water separator<br />Did a compression check<br />Ran engine out of a separate fuel tank (proved it wasn't the anti syphon or supply line filter in the tank.)<br /><br />Today did a fuel pressure test on the rail. Manual says should be between 34-36 psi. At idle and low speed hovered at about 31. At high speed (60 mph) the pressure dipped to 25 and it hesitated. <br /><br />Back at the dock after shut off, the pressure read about 25 - 30 psi for at least an hour. (Good sign not the VST or electric pump?)<br /><br />Took off hose that feeds the vapor separator tank from the lift pump and there was no pressure or fuel.<br /><br />Took off supply line at the mechanical pump and it was dry. Removed fuel/water separator filter and that was only 3/4 full. Thought there should have been fuel in all the above...<br /><br />Removed anti syphon valve and it was hard to blow through but it would open. Don't know how hard it should be so I'm getting a new one. As mentioned above ran from an outboard tank and still hesitated.<br /><br />My mechanic partner seems to think that either air is getting in somewhere around the fuel lift pump or the water separator or the fuel lift pump is malfunctioning. We thought it was the VST but now don't think so. What do you think?<br />Thanks, can't tell you how much you guys have helped me.
