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F70LA will stop running after 6 and one half mins.

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evinruderunner

New member
I just got a 2011 F70LA Yamaha that runs fine until it gets to 6 to 7 mins. Then shuts off.
Pressure at the fuel rail is 33 psi until it slowly starts to bounce and then drops to 0 psi.
The first owner has replaced the High and low pressure fuel pumps and the fuel filter above the low pressure pump.
The fuel assy on the motor has been cleaned, the fuel tank has been cleaned and new fuel is being used.
The pressure Regulator has been replaced.
The VST has been removed and cleaned, the float and needle valve have been replaced.
I have good steady spark all the way to shut off.
I have run the motor with the fuel cap off the tank and I have run the motor on a little 6 Gal tank, motor still stops around 6 mins.
I have the service Manual and have been reading everything I can find about the VST system and how the motor works.
I have tested the motor with the Yamaha YDS and can find nothing wrong.

Any help, Ideas, or just thoughts will be greatly appreciated.
 
evinruderunner said:
I just got a 2011 F70LA Yamaha that runs fine until it gets to 6 to 7 mins. Then shuts off.
Pressure at the fuel rail is 33 psi until it slowly starts to bounce and then drops to 0 psi.
The first owner has replaced the High and low pressure fuel pumps and the fuel filter above the low pressure pump.
The fuel assy on the motor has been cleaned, the fuel tank has been cleaned and new fuel is being used.
The pressure Regulator has been replaced.
The VST has been removed and cleaned, the float and needle valve have been replaced.
I have good steady spark all the way to shut off.
I have run the motor with the fuel cap off the tank and I have run the motor on a little 6 Gal tank, motor still stops around 6 mins.
I have the service Manual and have been reading everything I can find about the VST system and how the motor works.
I have tested the motor with the Yamaha YDS and can find nothing wrong.

Any help, Ideas, or just thoughts will be greatly appreciated.
Click to expand...


Given the six to seven minutes of runtime I would be looking at an overtemp shutdown circuit or a low oil pressure shutdown circuit. Either one of these if employed on this engine would likely shut the fuel off to protect the engine.
 
A faulty overtemp sensor will still shutdown the motor when it is operating in the normal range. Just saying it is worth a look.
 
evinruderunner said:
I just got a 2011 F70LA Yamaha that runs fine until it gets to 6 to 7 mins. Then shuts off.
Pressure at the fuel rail is 33 psi until it slowly starts to bounce and then drops to 0 psi.
The first owner has replaced the High and low pressure fuel pumps and the fuel filter above the low pressure pump.
The fuel assy on the motor has been cleaned, the fuel tank has been cleaned and new fuel is being used.
The pressure Regulator has been replaced.
The VST has been removed and cleaned, the float and needle valve have been replaced.
I have good steady spark all the way to shut off.
I have run the motor with the fuel cap off the tank and I have run the motor on a little 6 Gal tank, motor still stops around 6 mins.
I have the service Manual and have been reading everything I can find about the VST system and how the motor works.
I have tested the motor with the Yamaha YDS and can find nothing wrong.

Any help, Ideas, or just thoughts will be greatly appreciated.
Click to expand...
Did you ever determine what this was? I'm having same problem but just with idle, after almost exactly 45 minutes its shutting down. Running idle w/ the cover off it isn't shutting down. Increased the RPMs up to about 2000rpm, and it shut down in about 22 minutes.
 
mjmzk7 said:
Did you ever determine what this was? I'm having same problem but just with idle, after almost exactly 45 minutes its shutting down. Running idle w/ the cover off it isn't shutting down. Increased the RPMs up to about 2000rpm, and it shut down in about 22 minutes.
Click to expand...
Perhaps check the voltage going to the fuel pumps to see if it's an electrical (ECM, RELAY ?) problem.
 
Capt Roy said:
Perhaps check the voltage going to the fuel pumps to see if it's an electrical (ECM, RELAY ?) problem.
Click to expand...
Anything in particular lead you to that? Would that be something that seems to only give problems after a certain amount of time or after the engine warms up?
 
mjmzk7 said:
Anything in particular lead you to that? Would that be something that seems to only give problems after a certain amount of time or after the engine warms up?
Click to expand...
IF the fuel pump is electric rather than mechanical it would be perhaps energized via the ECM and a relay.
I do not have the schematic for this fuel system on Yamaha it is simply a guess from my 31 yrs in automotive.
 
I had a similar problem on a 2017 F50. In warm weather and under certain conditions my motor would shut down after about 6-8 minutes of run time. Took a lot of head scratching, but I believe I found the cause of my problem.

When my motor stopped, the VST had run dry. If I waited a few minutes the motor would start and run fine and then after 6-8 minutes the VST would run out of fuel again. If I released the VST vapour pressure using the schrader valve on top of the VST, the motor would start right away. If I left the motor idle for a few minutes and then run it, it seemed to work OK. Was more of a problem on warm days.

I believe my problem was that the VST was building up excessive vapour pressure and not allowing the needle valve to open preventing the VST from filling with fuel. The vapour pressure was high enough that the low pressure fuel pump couldn't push the needle open.
I know it sounds like a stretch, but if I removed the VST vent tube at the VST, the motor ran fine under any condition. I reattached the vent tube and the problem returned.

From my understanding, the fuel cooler is to address the warm fuel vapour issue. I flushed my cooler and it was clear. Next, I did a couple of things. Not sure exactly which was the fix, but I haven't had a problem since. I checked that all my VST vent lines to the solenoid valve and throttle body were clear and unobstructed. I replaced the solenoid valve. I had been using fuel stabilizer year round to prevent ethanol collecting water. This may have been misguided on my part. The stabilizer may have slightly increased fuel volatility, don't know. When I was trolling with my electric, I was tilting my motor for less drag. Now, I leave my motor down to keep it cooler. I shortened my black rubber fuel line to keep the fuel cooler. My fuel tanks are covered out of the sun for cooler fuel. On hot days, I let my motor idle for a few minutes to cool the fuel before running across the lake.

Which ever thing I did (one or all) has noticeably reduced the vapour pressure in the VST. Now the VST fills with fuel and the motor runs fine.
I hope there's something in this for you.
 
Roblin said:
I had a similar problem on a 2017 F50. In warm weather and under certain conditions my motor would shut down after about 6-8 minutes of run time. Took a lot of head scratching, but I believe I found the cause of my problem.

When my motor stopped, the VST had run dry. If I waited a few minutes the motor would start and run fine and then after 6-8 minutes the VST would run out of fuel again. If I released the VST vapour pressure using the schrader valve on top of the VST, the motor would start right away. If I left the motor idle for a few minutes and then run it, it seemed to work OK. Was more of a problem on warm days.

I believe my problem was that the VST was building up excessive vapour pressure and not allowing the needle valve to open preventing the VST from filling with fuel. The vapour pressure was high enough that the low pressure fuel pump couldn't push the needle open.
I know it sounds like a stretch, but if I removed the VST vent tube at the VST, the motor ran fine under any condition. I reattached the vent tube and the problem returned.

From my understanding, the fuel cooler is to address the warm fuel vapour issue. I flushed my cooler and it was clear. Next, I did a couple of things. Not sure exactly which was the fix, but I haven't had a problem since. I checked that all my VST vent lines to the solenoid valve and throttle body were clear and unobstructed. I replaced the solenoid valve. I had been using fuel stabilizer year round to prevent ethanol collecting water. This may have been misguided on my part. The stabilizer may have slightly increased fuel volatility, don't know. When I was trolling with my electric, I was tilting my motor for less drag. Now, I leave my motor down to keep it cooler. I shortened my black rubber fuel line to keep the fuel cooler. My fuel tanks are covered out of the sun for cooler fuel. On hot days, I let my motor idle for a few minutes to cool the fuel before running across the lake.

Which ever thing I did (one or all) has noticeably reduced the vapour pressure in the VST. Now the VST fills with fuel and the motor runs fine.
I hope there's something in this for you.
Click to expand...
Sounds like the solution. Quite thorough I might add.
Thumbs Up !
 
Another item that might be a factor. I use regular gas, which my motors base requirement. Lots of people insist on premium gas that use to be ethanol free.
The other benefit of premium high octane gas is it's less volatile. Resists burning to prevent destination (pinging). That would also reduce vapour pressure.
 
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