2002 ski nautique

My low pressure pump failed,  but not dramatically.  It started to stall out.  I pulled the output hose and confirmed it was flowing (I could even hear gas in the tank splashing as it returned to the tank.  However, when I did the volume test, it was low.  Put a new pump in and it solved the problem.

Can you hear gas splashing back into the tank with the low pressure pump on?

Sorry I can't give credit (couldn't find the post), but someone mentioned earlier to check the screen in the pick up line at the top of the tank.  I had this problem in my '96.  It got plugged, and I had tried and tested everything I could with no luck.  A West Coast Nautique service person suggested I check it before taking it in (didn't know there was one).  It was almost completely plugged.

Since your boat sat for so long, it could be covered in varnish, etc.

You've already proved that the high pressure pump works and the engine will run with gas in the canister.  

I would:

1. turn the low pressure pump on, go to the tank and listened to see if you hear gas flowing,  I assume not since if it's flowing back to the tank, it means it's also filling the canister.  If it's not flowing, you've got a blockage or a bad pump.

2. Check the flow from the tank to the low pressure pump.  I'd probably run some compressed air from the input side of the hose to the pump and see if you can get air bubbles in the tank.  If so, then you have some sort of flow.  If not, check the screen (it's at the top of the tank; part of the fitting that the line from the tank to the pump connects to the tank.  It's a small round metal mesh (my son (young at the time) was able to get his fingers in to pull it out; it was very plugged).  If you do that, check again to see if you can blow air through it. If you have an inline gas filter, replace it.  There should be no restriction in that line.

3. Connect the input hose back to the pump, disconnect the output hose where it connects to the canister, put it in a container, and measure the gas output (don't recall what it's supposed to be; in the service manual).  Visually my old one was fine, but it really wasn't.  If it's on the low side, replace it.

4. Check the return hose from the output from the canister (not to the injectors, but the large hose that returns gas to the tank).  Run compressed air to see if there are any blockages.

Since you confirmed the high pressure pump works and the engine runs, if you follow the above, you should hear gas splashing back into the tank from the return, which means the canister is full of gas and you should be good to go.

I don't see anywhere that you've unscrewed the fuel suction/pickup line from the tank.(Put a wrench on the big nut to hold it stationary and then unscrew the 90 degree fitting from that)

Then you'll have the line in your hand and be able to see if the suction inside the tank is plugged or maybe broken off, split, cracked above the fuel level like Gordon mentioned above.

And maybe Gordon should just give you his volume numbers or the page(s) in the manual if he wants you to do a volume check on that pump that seems to have run fine when you ran the engine for quite a while hooked to the outboard tank.

That's why pulling the tube is the best approach

Another group effort, hope it all works with the new tube, I think you'll be good, but maybe consider changing the hose between the anti siphon valve and the LP pump to a new A1-15 or A1-10 USCG approved marine hose while you're working on things.