98 gtx limited issue

[Riderrollin]

I have a 1998 seadoo gtx that will start and dies immediately if all fuel lines are hooked up as if ready to head out on the water. But womt stay running. But if it is gravity feed from an auxiliary tank it will start and run wide open.

When I bought it rge engine was in pieces and missing top end jugs. I bought a used engine with 144ish compression from a 2000 gtx. I replaced the stator from orginal engine to the 2000 3ngine I installed in the ski.

Had a fairly good battery that when dead trying to get it started (turned over never fired) purchased a new battery turned over start and dies immediately as if it fires coughs and turns off.

It has had the oil injection system deleted from purchase date and I kept it that way. Using premix 50:1 per some reading that's what most had said to use in this situation.

But with gravity feeding carbs with fuel into the intake line on fuel pump it starts and runs its wide open rpm I'm assuming do to gravity feed and open lines not connected sucking air.

I put key on post it beeps twice starts and dies instantly if all fuel limes are hooked up ready to go to the lake.

It does have a couple old crap seadoo fuel lines left on it going from fuel sending unit to fuel on reserve fuel selection switch (was waiting on new bulk fuel line spools to deliver) I did disconnect them run fuel thru them and air and fuel again they don't seem to have any collapsing issues nor did any gunk form inside lines come out when I pulled and cleaned but am replacing anyways. Was attempting process of elimination.

I pulled the fuel sending unit to see if it screen was clogged or unit was cracked screen was surprising pretty Clean magnet on floathad some rusted shavings stuck to magnet but circuit board for fuel levels appears to be in good condition. I still need to reassemble the sending unit and ohm test it..... tester is on a job forgot to bring it home.

Pump is good Impeller sun fine when gravity feeding carbs. I have looked best I can with mirror and phone fuel tank has no cracks. Tonight I did find the oil injection unction wires that connect to top of oil tank have been cut back tucked away and wired together.... I assume to complete a circuit but this is the first 2 stroke I have worked with that is premixed vs injection.

I'm not new to pwc or jet boats this has me baffled. I have wrenched on many and aparently I'm overlooking something obvious and just getting irritated. Needing a new prospective on this one.

Tomorrow's plan is to pull battery and get a good charge. Test fuel sending unit ohms, and replace fuel lines. Check all clamps double tighten them to prevent air or fuel leak. Any other ideas or thoughts?

 

[rusty nail]

maybe someone else can confirm this.....if the fuel pump is not working will gravity feeding the carbs work? the weight of the fuel in the aux tank may be enough to push past the fuel pump directly into the carbs.

 

[tobytd]

Rebuild carbs (per sticky…Mikuni parts only)
Run away on start up may be from air leak (carb base gasket?) or misadjusted idle screw or throttle cable.

 

[rusty nail]

Rebuild carbs (per sticky…Mikuni parts only)
Run away on start up may be from air leak (carb base gasket?) or misadjusted idle screw or throttle cable.

i did not read his running issue as a runaway, i read it as though he is able to run it with the throttle wide open. good point.

 

[TheGTIjetguy]

Rebuild carbs (per sticky…Mikuni parts only)
Run away on start up may be from air leak (carb base gasket?) or misadjusted idle screw or throttle cable.

Definitely replace all the old style fuel lines, the filter, and check all the clamps. Replace the fuel selector valve if your ski has one. They are known to leak internally.
Keep in mind, the fuel system requires 100% sealing from carb to sending unit.
The pump in the carb puts a small vacuum/siphon on the system that pulls fuel up out of the tank to the engine. Any leak will bleed air into the lines and defeat the vacuum.
TobyTd is right on. Rebuild carbs with genuine Mikuni kits. The pump diaphragms in the carb can fail, or the pulse line from the crankcase can fill the pump with oil and render it useless.
Good luck!

 

[jim6491]

Go slow, one issue at a time, I have the same ski and had a hard problem also. There is great help here and not so good. I used a vacuum pump with a clear hose to eliminate the fuel circuit by connecting the supply hose and return hose to the vacuum pump. Looking for flow issues and bubbles in the supply side. Next I checked the carb return to the tank with the vac pump for bubbles and they were there, BUT it does not matter! The carburetors were removed for their third time check. They have NON MIKUNI rebuild kits installed, that part was not the problem because the parts are identical to the original Mikuni parts and have since proven to be good. MY problem was the PTO carb plate return line orifice was plugged. I got great advice about how to clear it here at this website, and also extremely good information on how to set the high and low speed screws. THE vaccum pump showed the blockage, and it took several applications of carb cleaner and 40 psi of air pressure to unstop it. I believe the restrictor is about .031 so there is no easy way. The other problem was the high speed and low speed settings (for me) I found they had to be exact HS as per factory recommendations and the LS also needs to be exact and then adjusted very slightly + to eliminate bobble at half throttle. A related issue at the start of the problem was grey oily liquid which fouled the plugs, it took a couple days of using the started to spin the engine without plugs to remove the oil/water/ gas mixture. For me just a few pointers in the right direction solved my problem. I don't buy new plugs either, I just sand blast them and reinstall. It works great and better than $4-8 each.