Motor troubles

[Rookjd12]

I have a 2001 3.1 L Vmax 200 horse Oxy66 it started out this past spring and has continued to get worse at high-speed full out full throttle it shut down like somebody turn the key off some timeimes it is running when it comes to a stop and some time it isn't if it stops it starts right back up like normal and it jumped right back up and takes off like normal it may go 100 yards or 500 yards and then it happened again recently it has been shutting down at lower RPM, I think it is fuel related but I'm not sure, I have changed the 02 sensor and the primer bulb it idles fine just shut off at high rpm,any help would be greatly appreciated!!

[DennisG01]

I have a 2001 3.1 L Vmax 200 horse Oxy66 it started out this past spring and has continued to get worse at high-speed full out full throttle it shut down like somebody turn the key off some timeimes it is running when it comes to a stop and some time it isn't if it stops it starts right back up like normal and it jumped right back up and takes off like normal it may go 100 yards or 500 yards and then it happened again recently it has been shutting down at lower RPM, I think it is fuel related but I'm not sure, I have changed the 02 sensor and the primer bulb it idles fine just shut off at high rpm,any help would be greatly appreciated!!

Could you maybe read back through that and separate/clarify the main thoughts?

In the meantime, "Like somebody turned the key off" sounds electrical.

You said "running when it comes to a stop and sometimes it isn't". Does that mean sometimes it is stopped when it comes to a stop?

What is the fuel quality? How old... Any water... What additives... Etc.

[Jason2tpa]

I agree with Dennis. When the operator is saying the engine shuts down to mean it turns OFF, yeah sounds electrical. Shutting down from fuel starvation would normally exibit a winding down process, not an immediate shut down.

Have you experienced any other electrical issues with the motor, even those you believe not to be related to this problem?

[99yam40]

when the VST is out of fuel it will shut down like you turned the key off.

monitor fuel pressures look for restrictions and look for sucking air into the system

[Jason2tpa]

when the VST is out of fuel it will shut down like you turned the key off.

Really? No sounds of sputtering, or surging, before the engine completely starves?

[99yam40]

nope as long as it has fuel to pump it does what it should, when the fuel is gone so is the pressure on the rail

[rodbolt17]

yep I will second what 99 says.
it will shut down just like you turned off the key.
I have been on the boat when it did it.

first thing is monitor rail pressure.

[DennisG01]

Interesting. I've personally never had an engine shut down "like a switch" because of a fuel issue. There's always been some type of sputtering or loss of power first. However, I have no experience with my Yamaha shutting down to compare.

Curious... Will it ALWAYS shut down like a switch from loss of fuel? Is it possible that it could stumble before it shuts down, as well?

[robert graham]

It's been my experience that with a fuel restriction, the higher the RPM's the more the "light switch effect"....but then most fuel restrictions would show up at higher RPM's/fuel flow rates....

[99yam40]

depends on the type of motor.
If it has carbs, yes it will have some cylinders drop out before they all go away just because the top carbs will normally run dry before the lower ones.

EFI motors have the VST(Vapor separator tank) with a fuel pump in it to furnish solid liquid fuel to the rail. when there is no fuel left to pump there will be no fuel pressure to push fuel threw the injectors into the cylinders so each of the cylinders cannot burn anything.

think about it

[robert graham]

It's been my experience that with a fuel restriction, the higher the RPM's the more the "light switch effect"....but then most fuel restrictions would show up at higher RPM's/fuel flow rates....

[99yam40]

you are repeating yourself Robert, are you OK this morning?

[robert graham]

Old shaky fingers hit the button twice....We're snowed in here now and need to get the boat out and head for some warm sunny river somewhere!!!....

[rodbolt17]

not snowed in here but the wind is screaming and the air temp is about 34*f.
they expect about 23 or less later tonight.
suxs.

[99yam40]

It was 33 yesterday after noon here on Tx coast according to the thermometer on my F150 PU and about the same this morning and around noon as I went to store.

big change from last week here, was pushing 80 then