Re: How much fuel is enough
still troubleshooting my '81 mercury 115 straight 6 fuel pump. My mechanic is saying that the pump is not pumping enough fuel. When I have the line off of the carbs and crank the engine fuel spits out in little spirts. (does not look like enough) but I rebuild pump and then replaced pump and feul lines and bulb so i am now thinking maybe it is enough fuel and there was nothing wrong with it in the first place and to start looking at my carbs. How do you know how much fuel should come out of the fuel line at after pump when you crank the engine?
If the pump is assembled right and has a good fuel supply, it will pump enough fuel. The only definitive way to troubleshoot fuel delivery problems is to temporarily install a fuel pressure gauge, (unless you use an isolator) and run it. Fuel pressure needs to be over 1 lb and under 6 lbs at all times. If you don't tell her, you can swipe the gauge off'n grandma's pressure cooker to get the job done.
Many things affect fuel delivery, pickup tube including screen in the tank, fuel lines and filters between the tank and the engine, fittings on the engine, and even the pulse hose if any to the fuel pump. (Yep, it needs to be pretty tough rubber, a soft tygon hose won't work. Don't ask.)
