help fuel trouble

R

roadlooker

Cadet
Joined
Jun 30, 2011
Messages
15
i have a 1976 mercury 85hp haveing fuel problems comp on all 4 cylinders is 140 carbs have been rebuilt problem top carb doesnt seem to be geeting enough fuel had same problem before rebuiting carbs engine runs rough top carb doent adjust good and after running top two plugs seem almost dry repalced all the fuel lines ,tank, and squeze bulb could it be the fuel pump weak help at wits end.bottom two plugs wet and bottom carb ajust good
 
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: help fuel trouble

If squeezing the primer bulb improves performance that's a pretty good sign the fuel pump is ailing, however, continuing to run a motor with a weak fuel supply to that top carb is a recipe for disaster, that cyl will run lean and can melt the piston.

Disconnect the fuel hose to the carbs, point it into a suitable container and crank the motor, watch for a strong pulsed fuel stream, and less, rebuild the pump. Temporarily replace that hose with a clear hose, start the motor and watch for any air bubbles passing thru, indicating air sucking into the line somewhere before the pump.
 
You must log in or register to reply here.
Top