Just for a heads up, seadoo (any really) two strokes that won't stay running are telling you there is a problem. If you keep trying to run it after a shut down related to fuel, it will kill it. Lean fuel at WOT burns up more motors than anything else. The weak fuel flow due to the pump diaphragm causes a lean mixture to go into the piston. After you fix that pump, I'd check compression just to be sure it has not done any damage.
Kevin
Though this is partially right, the two stroke motors are alot more forgiving than any other motor built. Correct in saying that when they run then stall, there is a problem. Also, running at WOT when there is a problem will burn the cylinder up. But, when working with the 2 stroke that has a problem, as long as it is shutting down, it may be doing what's known as a "soft seize". These can be overcome by finding the problem and correcting it. You could lose a few PSI of compression, but the motor might still run for a few more years.
Manolocross hit the nail on the head. There is not suppose to be any fuel behind the pulse diaphragm. This side is directly related to the intake and exhaust stroke of the motor. Left unchecked, with a full fuel tank, gas can slowly dripple into the crank and fill it when idle. This does not mean the motor will not run, because the fuel pump is only there to supply fuel to the loop through the carbs, not actually provide a pressure to them. When the motor is cranked, or turned over, the vacuum (or manifold pressure) is what causes the needle valve to pop (hence pop off pressure) and allow the fuel to be "sucked" into the fuel chamber and jets. If the fuel pump diaphragm is busted out bad, it will not allow enough fuel into the loop for running the motor at all. The fuel will drain into the crank and prevent it from starting.
Running lean is usually attributed to bad carb settings or jets. Can also be caused from a leak at the intake, around the rotary (or reeds if 951) or even your casing. But, usually when the pump is bad, will not cause a lean condition that will damage the engine, since you have to run lean for a period of time to do severe damage. How much time? There is no certain amount that can be given, since there are so many different reasons and ways an engine can be damaged from a lean condition.
