Super Jet SUDDEN loss of power - info posted below

[zachweb]

I have a 1996 Superjet that is completely stock.

Playing around in water,I did a submerge, came up, made a high speed run for 15 seconds, turned and vhwoomph jetski acts like I lost a cylinder.

I am able to idle it back to shore and back to the trailer, and it acts like if I give it a little throttle, it's okay, but as soon as I get to turn enough to THINK about standing up, it tries to die.

Get it on the trailer, and it barely starts, and then sputters and runs roughly/poorly, but then SUDDENLY comes back to life it seemed.

Put it back in the water and as soon as the impeller loads up it's back to the poor idling problem.

I felt the cylinders, and they both felt like the same temperature

Get the boat home - spark check - VERY GOOD on both cylinders.

Pressure check 122-125 psi in both cylinders (this is similar to what it was last year with the same tester doing the same process - I'm also at 5000 ft elevation).

I check my 1 way valve and it allows air to flow freely both ways (I have one on order and can pull one from another ski to check if problem persists).

So...question, can a 1 way valve cause this sudden loss of power/do they just bust suddenly like that?

I've read that a proper/new fuel pump doesn't need any fuel tank pressure to work (I hope to have carb rebuilds coming soon anyways - it's summer and I need this thing running).

Some minor history before above problem:

Every time I first start this in the water after not running, it seemed to have a lean problem just off of idle (you'd have to feather the throttle a bit and then it would jump to life), but this would ONLY occur upon initial take-off (I just attributed it to a cold 2 cycle engine).

Also it would occasionally have a sort of bog issue any time I submerged it heavily (including the one in the incident above).

Up until this point I have not had any problems with this jetski, and it's incredibly snappy compared to anything else I've ridden (which isn't much ;-), including a '95 SN that has a 2001 engine in it.

Any advice would be appreciated.

Thanks!

 

[zachweb]

Still waiting for some suggestions.

 

[Poizen]

! way valve does what its call moves air in one direction yours is moving both so its needs replacing

the one way pressurizes the tank so fuel is forced to the carbs

now yours is broken it cant do that so yes i believe it is that as its starving for fuel


try this while you wait for new one blow on the end and keep pressure in there if it works you know your problem

 

[JT_Freeride]

Did you check for exhaust leaks? Also bypass your fuel selector by plugging the res line directly into the carb. The selector switches sometimes get gunked up and starves fuel. Make sure you try each one of these things by them selves so you can pinpoint the problem and fix it.

 

[zachweb]

Thanks guys. I'll try both of those. I've done the visible exhaust leak check. Nothing noticeable. Hard part is it'll run on land but you have to load the pump to really find out if you've fixed it. Water isn't too close by so it's a pain diagnosing.

 

[zachweb]

Got check valve yesterday. Put it on and it worked! Yay. Case closed.