any ideas on this 250??????

C

coastalboatworks401

Recruit
Joined
Jun 7, 2010
Messages
1
im working on a customers yamaha 250 v76 saltwater series fuel injected engine and can not seem to figure out what the problem is. the motor will run fine for about 10 minutes then starts surging like its running out of gas but its not. fuel system seems to be in perfect working order new plugs, o2 sensor, fuel filter and water separator, fesh gas. everything looks great. if anyone has any ideas or suggestions on what i should take a look at next please feel free to let me know. the only other things i can think of is the coil but im not sure im more of a inboard and fiberglass kinda guy. any help is greatly appreciated.
 
R

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: any ideas on this 250??????

appears to be working isnt a diagnosis.
what is fuel rail pressure at the surging RPM? what is O2 sensor output voltage at the surging RPM.
ign coil failures are incredibly rare.
in fact ign compont failure is very rare on that engine.
when was the last time the VST filter was cleaned? when was the last time the injector screens were cleaned or changed?
remember that engine runs on 5 cylinders from about 800 to 1200 RPM and on 4 cylinders from about 1200 to about 1800 RPM.
when trouble shooting dont let it bite you.
those 3.1L motors eat lift pump diaphrams, have you checked them?
 
cousinabe

cousinabe

Senior Chief Petty Officer
Joined
Nov 13, 2001
Messages
765
Re: any ideas on this 250??????

i will only add to rodbolts recommendation: what's the fuel pressure at the vst schrader valve when problem is occurring?
 
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