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DF40 Vapor Separator Issues 1999 model

Bob Moors

New member
I have not used this engine in several years. I replaced the electric fuel pump inside the vapor separator. The engine idles fine and runs upto about 2500 rpm, then it starts cutting in and out like the fuel is cutting out. In the very bottom of the unit under a plate is a small $200 part call a surge device. Not sure it I need to replace this and at $200 cost would like some way to test if this is the issue. I wish they made is easier to work on, take half the thing apart to change a fuel pump.Any ideas what my problem might be?
 
You mention 2500 rpm. A magic number when working with Suzuki 4 strokes.
That's when the rev limiter kicks in.

If the engine EMM "thinks" the engine is in neutral, it will not let the engine rev up. Surges strongly.

So, look on the throttle/shifting linkage, locate the neutral safety switch, and check it for proper operation.

I would suspect, from your description, that the switch is stuck.

By the way, that part under the plate inside the vap. sep. is the fuel pressure regulator.
 
Thanks, I finally figured out about the rev limiter. I thought it would just hold it at a constant rpm not cut in and out.I can not believe the cost of the fuel pressure regulator $200 for a $10 part.Thanks for your reply
 
So it was a stuck neutral switch? Or was rev limiter kicking in for some other code?

Yes....prices are unbelievable for these parts. I have found """some""" aftermarket parts tht fits these motors.

Some prices are 10% of the list Suzuki part. You Old Timers remember "usury laws". Where did they go off to?
 
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