Re: Optimax 225 surging?
You mentioned the bulb gets flat or soft once or twice. Is this during the initial 15 minute cold start warm-up period?<br /><br />Its possible the initial fuel pump (diaphragm type) is having an issue. It only pulls about 3 psi and its job is to keep the vapor separator tank filled so the medium pressure fuel pump in the bottom of the VST gets nice, undisturbed (and unbubbled)fuel input. You can install a high pressure fuel gage on the output of the hi pressure fuel pump. You should see @ 100 psi all the time, regardless of being at idle or on plane. Regardless of any of the various sensor readings to the ECU, if the engine is up and running there must be a stable supply of both fuel and compressed air and a very specific differential of about 10 psi between the two. If these pressures are not at a near constant level you will have problems. If the fuel pressure varies it indicates some sort of fuel delivery issue at either the low pressure diaphragm pump, the mid pressure or hi pressure pumps. Or possibly even the antisiphon valve limiting fuel (thats why the bulb gets drawn down probably - the engine is sucking on one end of the bulb and the other end is functionally pinched off so the bulb is literally sucked dry.) But why that would only stick initially is past me. But fuel pumps on the other hand, they can change behavior as they go from cold to warm and so can pressure differential or "trailer diaphragms" which maintain the constant 10 psi pressure differential between the fuel and air systems. Until the flow is relatively hi (on plane at high rpm) there may be an issue with the valve that regulates the 10 psi delta. Any dealer who does Optimax will have a simple device that hooks into schrader valves on your engine and has two pressure gages. This will show the pressure of fuel and air and the differential between them. On a cold start on a garden hose you should have this checked. Or at your dock if you can coax a tech and the equipment out there. They also have a laptop computer they can plug in that has diagnostic capability. Having that hooked up right as the cold motor is started may reveal crazy sensor readings.<br /><br />Good luck.
