Suzuki 20 HP DF20AES2 fuel delivery issue

So, I was out on the lake today in my '62 AlumaCraft Model K and I'm starting to head back to the launch area to head home when my 2018 DF20A starts sputtering and coughing and comes close to dying. The only way I can keep it running at all was to keep wide open throttle, and it was bucking like a drunk mule. I checked the fuel level - no problem there, and I was at wits end about how I was going to get back to the Jeep because whenever I put it in forward the revs would drop off and it would start to die again. Finally I tried pumping the prime bulb, first once and then continuously, and found I could get it to run "smooth enough" at about one third throttle if I pumped the prime bulb constantly. It took a while and my hand is sore, but I made it back to two miles to the launch ramp and made it back home.

Where should I start troubleshooting? I don't have a Suzuki Marine service shop for 250 miles.

Bump? Still trying to figure this out.

Fuel delivery issue? Have you replaced the fuel filter lately? Is it possible you picked up some water in your fuel? Pickup in the fuel tank partially plugged? Kinked fuel line? Loose fuel connection allowing air to enter the system? Plugged vent on the fuel tank? I’d start at the tank and inspect every inch of your fuel line looking for any abnormalities. Check the easy/cheap stuff before getting deeper into the fuel system.

I'm sorry, I should have updated the original post yesterday. I had just gotten back from the lake and was kinda wound up about having to nurse this baby home, as well as the expected level of stupidity one finds around launch ramps on the Forth of July weekend. I have replaced the fuel tank, the fuel line from the tank to the motor, and the fuel filter. There are no kinks or abnormalities that are visible in the fuel line path. Today I will be replacing the low pressure fuel pump and removing, disassembling, cleaning and inspecting the high pressure fuel pump. After reading repair forums obsessively for most of the evening, I have come to believe this problem may be related to the high pressure pump. One cylinder runs consistantly - the second cylinder seems to be the problem child. When this problem started the only way I could get the motor to run at all was to constantly work the pressure bulb in the fuel line. Since changing the items noted, the motor issue had morphed into a thumper with the second cylinder working only intermittantly.

Could be the ECM limiting the revs in a fail safe mode. I believe that is accomplished by limiting spark. I’m assuming no codes otherwise you would have mentioned it. Revs are limited to 3000rpms for routine codes and 1000rpms for major stuff like low oil pressure. In around 2018 Suzuki was offering 6 year warranties as a special incentive, maybe you’ll get lucky and whatever is causing you grief is covered under warranty.

A fuel pressure check would save you from disassembling the VST if your fuel pressure is to factory specifications. These Suzuki’s need a good solid battery, they will act up in all kinds of weird ways if a solid 12V isn’t provided

William01 said:

Could be the ECM limiting the revs in a fail safe mode. I believe that is accomplished by limiting spark. I’m assuming no codes otherwise you would have mentioned it. Revs are limited to 3000rpms for routine codes and 1000rpms for major stuff like low oil pressure. In around 2018 Suzuki was offering 6 year warranties as a special incentive, maybe you’ll get lucky and whatever is causing you grief is covered under warranty.

A fuel pressure check would save you from disassembling the VST if your fuel pressure is to factory specifications. These Suzuki’s need a good solid battery, they will act up in all kinds of weird ways if a solid 12V isn’t provided

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Thanks for the reply. No codes or warnings from the LED. When the second cylinder cuts in at random it runs like a champ - until it cuts out again. In one cylinder mode it doesn't matter what you do with the throttle. As far as warranty, there is no Authorized Suzuki service available for about 200 miles so I think I'm on my own.

Your first post sounds like a fuel delivery issue, your post #4and #6 sounds like a spark issue. Is the spark plug thats not firing wet? When was the last time your spark plugs were changed? If your high pressure fuel pump was starting to fail would it not affect both cylinders? Have you tried running Seafoam or a similar product through the fuel system incase you’ve picked up some water?

While I was changing the lp fuel punp and removing, disassembling, inspecting and cleaning the hp fuel pump I pulled both spark plugs and inspected them. They both looked really good, as I expected for a motor with this few hours on it, so I hit them lightly with a wire brush and reinstalled them. I then put an engine flush adapter on the motor and ran it in my driveway. When I pulled the top spark plug wire there was no change in it's idle. Then I replaced the spark plug wire and pulled the upper fuel injector electrical connector. Still no change in idle. Then after I put the injector connector back on I was poking around that area and found that I could push on the injector connector and actually rotate the injector body, and when I did this the idle increased and smoothed out. Yay. So, my next effort will be to swap the injectors and see if the issue follows the upper injector body.

Swapped injectors and top cylinder still not firing. This has to be electrical.