Please help diagnose my DF115A

[bginvestor]

When I bought my pontoon, little did I know that the closest Suzuki dealer was over 5 hours away! yikes! I could use some. This is a 2013 DF115A.

Symptom:

1) After 2000 RPM, hesitates under load and not under load. Under load, RPMs bounce up and down 500 to 600 RPMS. It seems to run to full power, than power will just go away and bounce back up. With no load, increasing RPMs slowly, it sounds like the motor is kinda misfiring sometimes.

No issues with start-up , idle sounds good, and temperature seems to be running normal (not getting hot).

I plugged into SDS; and results show no error CODES, with no errors on any sensors.

This engine only has 45 hours, and it has been sitting for 1.5 years! I thought for sure it was the VST, but my surprise, its very clean inside. I went ahead replaced with with a NEW VST assembly.

Still have the exact same symptoms.

New parts.

a) ejector grommets
b) low/high fuel lines purged
c)new manifold gasket
d) new VST
e) new low pressure filter
f) Injectors should be ok, since I verified by installing another set with no change to the symptoms. I have switched back to the original set.

Items checked:
IAT -> Ohms Ok
COIL (primary/secondary) = ( ohm ok/ ohm ok)

Plan to check low pressure fuel pump pressure.

Any suggestions?

Thank you.
Brian

[artdf175]

usually before spending a lot of $$$ on parts you need a little more analysis of the problem
First, the service manual - hopefully you acquired one

This is sounding to me like a fuel related issue
does this symptom start immediately after starting or does it take a while to start doing this?
condition of the fuel bulb? does it go flat?
check all fuel hoses for good solid tight clamped connections?
when running the engine - observer the inline fuel filter-- any air or air bubbles?
Art

[bginvestor]

usually before spending a lot of $$$ on parts you need a little more analysis of the problem
First, the service manual - hopefully you acquired one

This is sounding to me like a fuel related issue
does this symptom start immediately after starting or does it take a while to start doing this?
condition of the fuel bulb? does it go flat?
check all fuel hoses for good solid tight clamped connections?
when running the engine - observer the inline fuel filter-- any air or air bubbles?
Art

Hi Art,

Thanks for your feedback. I have studied the DF115A manual.


"This is sounding to me like a fuel related issue ".

I agree that's why I bought a VST in anticipation of a fuel regulator or high pressure pump problem. The pumps can run, but sometimes not fully pressurize. Currently, I am trying to rule out fuel system.

I get a good , solid 42 psi on the high side (new VST) ; and ~3 psi on the low side. This is at idle. I have shorten the fuel lines, and using fresh gas. I've purged all the lines, and I don't think they are crimping. Since I had the manifold off, I decided to replace the VST in case the regulator was faulty at higher RPM's.


"does this symptom start immediately after starting or does it take a while to start doing this?"
starts immediately cold or hot


condition of the fuel bulb? does it go flat?
yes, goes flat

check all fuel hoses for good solid tight clamped connections?
yes, new lines, and shortened; fresh gas

when running the engine - observer the inline fuel filter-- any air or air bubbles?
no air bubbles

I am starting to think its not fuel related. I am noticing poor throttle response if I throttle quickly compared to slowly. Dang. I hope its not the ECM... ;(

[bginvestor]

Here's a video to show the poor throttle issue.

I started it up, and did two quicker throttle ups.. the throttle response is poor, after, went back to idle ..


https://youtu.be/-hjD-59NCr4

Any feedback, greatly appreciated. sounds like I'm saying " F%^&%&" at the end of the video, but I'm really saying stop for my kid to stop recording. lol

[catacom225]

You must eliminate all fuel related as Art suggests, replace primer,should not go flat, check if the fuel tank is breathing properly and that the fuel strainer in the tank is clear. Try running it on a separate auxiliary tank , also remove the air box and make sure the throttle is clear

[artdf175]

the bulb going flat is a classic example of a tank vent not working properly. the other thing that has turned up here over and over is an anti siphon type device on the fuel tank that is not working and not allowing tank to breathe.
what is happening with the fuel bulb going flat is the low pressure fuel pump pumps all the fuel out of the bulb until basically the engine starved itself out. If the engine runs at all the high pressure pump is working

the other question is the type of fuel tank
portable tank or built in permanent type?
have a water/fuel separator?
Art

[bginvestor]

Art,

Per your recommendation, went back and reassessed the fuel lines. For the last week, I've been using a new primer, and temporary tank. The hose lies in the bottom of the 2 gallon tank, and open to atmosphere. Very careful not to let dirt in.

I noticed the joint transition from 3/8 to 1/4 actually was looser than I thought! Replaced with a better hose clamp. Seems to run better when I checked for a few minutes this morning! Time to try it out on the lake tomorrow! I'll report back. Thank you!

By the way, I have been very hesitant to run the prop with water hose at higher RPM. What's the highest RPM I should run with it in gear? The ECM does limit RPM in neutral, so having it in gear might be required to fully assess the situation.

Catacom,

Thanks. My pontoon tank has gas that's probably 1.5 years old. Did not want to use. The system will be cleaned up , and will have a upgraded water separator as well.

[artdf175]

Running off the hose; I would not run it much over 2000 rpm and only briefly. If you have a boat ramp close by- take it there and you can run it as fast as you want
your fuel bulb going flat-- couple of things make sure the fuel flow is the correct direction and it is vertical with the engine side at the top
the other thing on the new fuel tanks is an anti siphon device -- take and punch out the ball bearing and spring
then run for 10-15 minutes and check the fuel bulb
The other thing that I recently discovered is the fuel line.. the new fuel lines have a plastic liner on the inside -- it is very easy to plug the fuel line by inserting the end connections/bulb into the ends and pushing this liner back up the hose to the point of blocking the fuel flow.
so by running it a while, if the fuel bulb goes flat or the sides of the tank start to get sucked in, you know you still have a problem
you get the fuel delivery solved and I think you will be a happy camper.
Art

old fuel-- pump it out and run it through you car
when you get to the last of it-- pump it into something line a gallon jar so you can check for contaminants and water - if looking good I would put another gallon of good fuel in an rock it around pump it out - your water/fuel filter will get anything else

[bginvestor]

Success!

DF115a runs perfect now! It was definitely a fuel issue.

I'm leaning towards that it was the high pressure fuel pump because the engine had the same symptoms when connected to both main and aux tanks.

Thanks for the advice!
Brian