Mercury 90hp 4 stroke (Runs for hour, dies, no start or rough start then dies)
Mercury 90 hp serial number: 1B950975
Engine will run for a while and then all of a sudden develop a rough idle or die. No start or start with rough idle only to die again. Seems like it is running out of fuel or pump can't keep up. Float was replaced by dealer per a bulletin. The problem seems to be intermittent. Topped off with fresh fuel. Fuel is good. Help!
Ok, dealer replaced float switch and the lift pump now and it is still having the same problem. Help!!! Will run for a while and then all of a sudden after idling for minute or so, it just dies.
Have you checked your fuel lines?
New fuel lines were installed.
If you have a timing light you could try hooking it to the different plug wires when it quits. Crank motor and see if some of the cylinders are not firing or firing erratically. I'd suggest pulling the spark plugs when the motor acts up but that would be hard to do on the water.
Does the problem only occur when the engine is at full operating temperature and does it have to cool off completely to get it to run normally again? Did your mechanic download any fault codes whe he was trying to diagnose the motor? This could indicate a electronic or electrical component overheating. The problem could be in the ignition or the fuel injection side.
We have narrowed it down to fuel module. We installed an electric full pump inline on a switch. When the engine begins to die, we flip the switch and it cleans up and runs perfect.
And what PRESSURE rating is this fuel pump?Originally Posted by Psychologist
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
Low pressure
That would indicate that the FSM is low on fuel, an indication that the float switch is not functioning properly, the low pressure pump is failing, or there is a fuel supply restriction.
Float switch should NOT be "presumed" good, even if it was just replaced.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
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