Df90 - gas in oil

[jeffro22]

Df90 is getting gas in oil. Verified fuel coming through vent hose off vst while running. Planning to take vst apart and replace needle valve assembly. Anything else I need to look at or replace while it’s opened up.

Anything to prevent this from re- occurring?

[pniksnut]

fuel in oil can also accur when the thermostat is broke . the engine stays to cold

[artdf175]

It may be as simple as the float valve being out of adjustment
so before throwing money at parts check that first

[jeffro22]

fuel in oil can also accur when the thermostat is broke . the engine stays to cold

in this case I have verified fuel from vst which seems to be a common issue with this motor. I think I did see something about running a hotter thermostat to help with fuel dilution if issue isn’t vst related

[jeffro22]

It may be as simple as the float valve being out of adjustment
so before throwing money at parts check that first

I’ll try to see if I can locate a Manual but how is best way to verify this?

[Moonlighter]

Link to manuals for K9 models 90-140.

https://www.dropbox.com/s/zlj6fluwnb...email.pdf?dl=0

Since you have verified that fuel is running out the vst vent tube, then thoroughly cleaning out the VST and resetting float level is the solution. Tiny screen filter in there to be cleaned as part of that job.

The best way to reduce likelihood of this happening again is to install a water separating fuel filter in the fuel line between tank and engine (eg RACOR style) and to change the filter element regularly.

I would also change out all the on-motor low (white) and high pressure filters (the black one) since there is obviously a fuel contamination issue in play.

[jeffro22]

Thanks for posting info on manual. Is it worth trying a high concentration of ring free or sea foam though the fuel system first or is that waste of time?

when servicing vst should I check the regulator also? Also noticed it recommended sealant when putting back together. I have always just used a new gasket. Do I need to pickup that sealer also?

[Murray]

https://www.suzukioutboardforum.com/...115-vst-thread

If your float/needle are in need of adjustment then nothing from a bottle will work.

[jeffro22]

Got vst out and separated not sure what the issue is because to me it looks really clean and I don’t see any wear of dirt on needle or seat. Will check float height

the black rubber grommet seal on top of high pressure pump is swollen and slightly cracked so will plan to replace that while it’s apart

a little worried putting it all back together without seeing anything definitive on the issue.

Float actually seemed a little out of adjustment, so got that to the 43mm mark with digital calipers. original Measurement was almost 47mm (assuming I am measuring correctly)

[jeffro22]

Ran boat today for about 20 mins and then pulled vent hose and didn't get any fuel. I ended up doing new needle and seat, adjusted float height, and new high pressure pump bushing,, new VST gasket and put back together

did an oil change and also added a racor fuel filter

So far so good

[Moonlighter]

Good move adding the RACOR. Efi engines just dont like dirty fuel.