The tip of the plunger chips off from the backwash when you let off the throttle too quick. All that fuel is moving, and when you let off, it has no place to go. Just like huffing a turbo. If you want to bypass, just pull the spring and plunger, and put the solenoid back in.
You can't clean the rubber off the end. There is a hole in the end of the metal part of the plunger. I saw where somebody removed the rubber and welded a small nut on the end of the plunger. I removed it and welded the hole shut, then ground it smooth. Sometimes mine still "diesels" to a stop, as opposed to shutting off quick.
