98 DT 115 cutting off at idle and high speed

[Briggs@23]

Just got my Suzuki DT115 EFI out of the shop after three weeks. Replaced the high pressure fuel pump (600.00), diaphragm pump and spark plugs. It will crank and idle but dies after a little while. After a while I can get going and plane out but it will just die on and shut off. Just looses power and shuts down. No pattern about it. It will recrank. If I keep pumping the bulb it seems to run better. Any help? Could it be the throttle position sensor. Man I hate bring it back to the shop and missing the rest of my summer.

[Solarman]

Could be those clear plastic check valves in that diaphragm pump they probably missed/ didn't look at?

If cracked or breaking up, it will not pump fuel well, and if pieces come loose, they may get caught on backside of needle valve, restricting fuel flow at any speed, most noticeable when/ at wot, acts like not enough fuel/ surging.

Likewise, if fuel pressure at rail was the original problem before, it may have been the pressure regulator at fault, not the HP pump itself.

I don't know the original reasons the shop had the boat? But I guessed it had a fuel issue in the beginning?

Anyway, they don't sell the clear disc check valves for the diaphragm pump, so they would charge for a new pump if they're bad ($200, plus install). And (you may need to look at parts diagram?), the fuel pressure regulator, I believe, is mounted at the top of your fuel rail with multiple hoses. Not sure the cost of ($40?).

So basically, if you took it back they would charge you maybe another $300 plus? Would you get anything back for what they did? Doubt that.

I think I would replace the regulator myself. Cheapest part. See how it runs? If still acts up, I'd open up the diaphragm pump and inspect those disc(s). If either disc is broken replace pump. If any pieces of those discs are missing, then good chance they are lodged at needle valve.

I would test run before opening vapor separator tank, just to see.

Now, your throttle valve sensor (TVS) advances/ retards timing corresponding to the position of the throttle valve. If your throttle skips, bogs when giving throttle, pull it back, push it forward, doesn't seem to make a difference, or if motor idles fine, put in forward and slowly increase motor increases accordingly, then a blank spot, no increase, then pushing past that spot motor jumps to life again.

This might mean a bad TVS? But motor needs to be running good. Hopefully it was tested by mechanic?

Well, I've said a bit. I think with your telling me, pumping bulb makes a difference, then fuel tends to answer that. I've pieced the parts you mentioned, to fuel related issues. Hope you can understand all of what i'm saying?

Good luck.post back after reading all this a few times.