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40 hp 4 stroke turns over, will not crank.

S

shanemedearis

New member
Motor was running fine. I turned it off. Five minutes later I tried to restart it and it would not start. It turns over but will not start. At this point I checked to make sure it was getting fuel and it was. Next I check to see if it getting fire. So I pulled the plug held it to metal part of the engine to confirm the plug was firing. When I turned the key it cranked up on two cylinders. So I turn it off put the plug back in and turned the key, turns over will not crank. So I pull the plug back out and it cranks on two cylinders. This time I take the plug wire off the plug and with the engine still running I try to put the plug back in the 3rd cylinder and as soon as I put the plug in the motor goes dead and will not crank until I pull the plug out. Sound crazy and make no since. I even stared the motor with the plug out and stuck my finger in the plug hole and it immediately died. Any thoughts on what would cause this and or how to fix it. Thanks.
 
Assuming your model is MFS40A. Turns over and cranking are the same thing. I assume you mean that with all 3 plugs in it does not start. Which cylinder did you take the plug out of? Does it behave the same way if you take out a different plug? How did you verify fuel?
 
This is confusing and quite unbelievable. The motor stops when you plug up the spark plug hole with your finger? Will it start with the affected cylinder's plug wire removed from the plug? Any spark issue on this motor is probably gonna need a new control module.....power pack. These can act up without warning. Make sure there are no bad looking wires or a faulty ignition switch, or power crossing to the kill circuit. These are not too expensive.....maybe $160. If no spark on only 1 cylinder, and the others are still sparking, then it's almost a "given".
 
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pvanv said:
Assuming your model is MFS40A. Turns over and cranking are the same thing. I assume you mean that with all 3 plugs in it does not start. Which cylinder did you take the plug out of? Does it behave the same way if you take out a different plug? How did you verify fuel?
Click to expand...

Thanks for your reply. I took the plug out of the top cylinder. #1 I assume. Have not tried a different cylinder. I will do that in the morning and post results. I only verified that the was making it to the clear feul filter. Then it cranked on two cylinders so I did check any futher.
 
Can you take out all spark plugs, then check to see that each cylinder, while cranking with a battery at least 12.6 volts (fully charged), will jump a nice crackling blue/white spark at least 7/16"?
 
pvanv said:
Assuming your model is MFS40A. Turns over and cranking are the same thing. I assume you mean that with all 3 plugs in it does not start. Which cylinder did you take the plug out of? Does it behave the same way if you take out a different plug? How did you verify fuel?
Click to expand...

Yes it acts the same way if you take any one plug out it will crank and run, but it will only idle (roughly) if you try to give it fuel the engine dies. I began checking the feul supply at the pump ball. The at the clear filter. Move from there to the vacuum type feul pump, it was working. From there I unplugged the electric pump and got no feul so I plug it back in and had feul. From there I check thecfeul rail pressure/beading valve and it had pressurised feul there.
While testing the electric feul feed pump. I unplugged it and the and the engine started and idled. (All three plugs where in at this time) when I pluged it back in the engine dies. It appears that when the pump is plug in the computer tells the injectors not to fire. Any suggestions. Sorry for the delay.
 
All plugs are firing. it acts the same way if you take any one plug out it will crank and run, but it will only idle (roughly) if you try to give it fuel the engine dies.
I began checking the feul supply at the pump ball. Then at the clear filter. Move from there to the vacuum type feul pump, it was working. From there I unplugged the electric pump and got no feul so I plug it back in and had feul. From there I check thecfeul rail pressure/beading valve and it had pressurised feul there.
While testing the electric feul feed pump. I unplugged it and the and the engine started and idled. (All three plugs where in at this time) when I pluged it back in the engine dies. It appears that when the pump is plug in the computer tells the injectors not to fire. Any suggestions. Sorry for the delay.
 
pvanv said:
Assuming your model is MFS40A. Turns over and cranking are the same thing. I assume you mean that with all 3 plugs in it does not start. Which cylinder did you take the plug out of? Does it behave the same way if you take out a different plug? How did you verify fuel?
Click to expand...
<br><br>Yes it acts the same way if you take any one plug out it will crank and run, but it will only idle (roughly) if you try to give it fuel the engine dies. I began checking the feul supply at the pump ball. The at the clear filter. Move from there to the vacuum type feul pump, it was working. From there I unplugged the electric pump and got no feul so I plug it back in and had feul. From there I check thecfeul rail pressure/beading valve and it had pressurised feul there. <br>
While testing the electric feul feed pump. I unplugged it and the and the engine started and idled. (All three plugs where in at this time) when I pluged it back in the engine dies. It appears that when the pump is plug in the computer tells the injectors not to fire.  Any suggestions. Sorry for the delay.
 
Um. There isn't any vacuum type fuel pump. There is a low pressure mechanical fuel pump that runs off the cam. What was the fuel rail pressure? Have you checked for signal to the injectors, using your Factory service manual as a guide? Injector power should have nothing to do with the FFP being connected or not.
 
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