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View Full Version : Gas going into intake manifold not from carburetors 1989 100Hp Mariner



medelman2k
04-13-2013, 04:29 PM
Hi I really need someone's input here. My 1989 Mariner started flooding the bottom piston when you squeeze the gas bulb. I thought it was the carburetors so I rebuilt them. Still had the same problem. So I took off all the carbs and plugged the carb gas line and squoze the bulb and sure enough the manifold filled with gasoline. What part has failed here? Fuel Check Valve? I have the carbs off and I am about to rebuild the fuel pump, but I need some assistance to know what else I may need to do. Feeling slight depressed after carb rebuild, was anticipating success.

medelman2k
04-13-2013, 06:06 PM
Could this be a leaking accelerator pump?

medelman2k
04-13-2013, 08:13 PM
Hi I really need someone's input here. My 1989 Mariner started flooding the bottom piston when you squeeze the gas bulb. I thought it was the carburetors so I rebuilt them. Still had the same problem. So I took off all the carbs and plugged the carb gas line and squoze the bulb and sure enough the manifold filled with gasoline. What part has failed here? Fuel Check Valve? I have the carbs off and I am about to rebuild the fuel pump, but I need some assistance to know what else I may need to do. Feeling slight depressed after carb rebuild, was anticipating success.

Update: 6 hours later, after a lot of trouble shooting and isolating the problem, it is the fuel pump. Apparently when Mercury fuel pumps diaphragm fails, it dumps gas into the intake manifold. Wow, I wish I knew this 10 hours ago.