Tweet
I have a 2006 f250txr motor starts and runs perfect. The problem is shortly after starting motor. (Less than 30-60 seconds)it starts pouring fuel out of the starboard side from a small hose right at the cowling latch handle. I was told this was an overflow hose for the vst. That it is designed to dump excess fuel rather than flood the motor. And the needle valve in top of vst likely had small peice of trash stoping it from closing all the way. I removed vst to clean and it looked spotless inside. No tarnish or residue in tank no signs of trash filter looked brand new. Needle valve looked great. Put back together and same problem. Motor starts and runs perfect yet starts pouring extra fuel out of the side of the from that hose on the latch.
-
-
clearly the VST is being overfilled until fuel rises out through the top vent and through the carbon canister.
If the float needle valve is not in some way defective,
then it must be that the incoming pressure is forcing the needle valve open
alongside the lift pump is a 'relief valve assembly'
designed to regulate pressure supplied to the VST
that may have failed closed
https://www.boats.net/catalog/yamaha/outboard-by-hp/250hp/f250txr-0406/fuel-injection-pump-2
-
I am not sure how much pressure it should take to open that relife valve. I can not blow it open by mouth. But if use a small allen wrench the ball inside seems to open and shut very freely. Took apart the vst again to double check cleanliness and correct assembly and every thing appears correct. I have never seen this before. I did find an old post on here from several years ago with a guy describing the exact same issue. Everyone was telling him it had to be the needle valve or the relife valve. He claimed to have taken apart put back together cleaned and aligned several times untill he finally ordered brand new vst complete assembly and relief valve and still had the same problem. Everyone seemed very frustrated with him so he stopped posting to the thread with no fix ever found. Is there any other component or situation that could possibly cause this fuel to be pumped over board like this?Comment
-
I don't think so.
There can be different problems with the venting of the VST -
but I don't think they can impact how high the level of fuel rises in it.
Either the needle valve doesn't seal -
or it doesn't get closed by the float -
or it get forced openComment
-
It is designed to prevent over flow fuel from collecting under the cowling. Or in the intake manifold. Where a ****y tiny spark can cause big boom.Originally posted by Brandon B View PostComment
-
Ok. Well thanks your your time. I am not sure what my next step will be. I could understand if this was intermittent or was just a small leak or the fuel system was dirty with signs of trash in it. Or if this had been a long term issue. But this is pumping fuel overboard as if you had a designated pump to do it on purpose. It just started doing this out of the blue. And everything internal looks immaculate! And after reading thet old post where he said he put all brand new complete fuel system on his and still had same exact issue it just really has me baffled. But i do sincerely appreciate you taking the time to think about my problems. If i ever figure it out i will co.e back and post my findings!Comment
-
faiedeal, did you ever instrument your motor to see what the output pressure of the low pressure pump is and to see what the opening pressure for the relief valve is?Comment
-
It is designed so that if a component fails the gasoline will be pumped over board (outside of the upper and lower cowling) to prevent gasoline from collecting inside the cowling.Originally posted by Brandon B View Post
A failing VST float valve could do it, a LP pump that outputs excessive pressure might do it, a relief valve that is not relieving might do it. Yamaha almost never publishes failure modes and effects analyses.Comment
-
Here is a diagram of a very early Yamaha four stroke motor with a vapor separator tank. In this model if the VST float needle valve were to not close then raw gasoline would be pumped to the intake manifold. Hopefully excess gasoline would cause the motor to run overly rich and kill the motor. But then if someone removes the top cowl to investigate, and has a blunt hanging from his lips, fuel vapors could ignite. It has happened. As a safety measure Yamaha routed the VST vent lines so that any fumes and gasoline would not collect within the motor.
Comment
-
yes, below is a link to the videoOriginally posted by boscoe99 View Post
with the engine off, and the VST drain plug removed,
the pump quickly filled the VST until the float valve closed and 'dead-headed' it -
at which point the pressure regulating valve came into play.
Looks to be ~14 psi on my original 2004 valve
https://vimeo.com/268813753
Recall how in the yearly "Marine Technical Guide"
there would be a "mini" Service Manual for each new model?
when the 3.3 F250 was introduced -
using the same "Relief Valve Assembly" as the F200/F225 -
(was that the 2004? 2005? I don't have it handy)
that section included this chart:
Comment
-
Thanks.
Before I die I hope to complete my searchable Yamaha data base. An excel file where one can find a topic by name (same EFI fuel pump) that is then hot linked to Yamaha data where information about that topic can be found. A work in process. My memory will no longer let me recall where I previously read about something.
I could swear that there is a Yamaha article about the whys and wherefores and ins and outs of all of the things that cause bonding wire burning. I have not yet been able to find it. The search continues.Comment
-
yes, an interesting topic.Originally posted by boscoe99 View Post
"Intuition" says it has to be 'a ground problem' - but exactly what/where is a puzzler
I can only recall reading of one case where the final 'solution' was found and reported:
the engine had a 'rigging tube'
which somehow lacked protection where the battery cables entered the cowling;
from repeated contact with the edge of the sheet metal lower cowling,
the insulation of the negative battery cable was scraped away,
and even some of the strands of wiring cut -
eventually resulting in a better ground path,
back to the battery, via the cowling/midsection/bracket
instead of the lug on the engine block.
But even that 'pathway' is murky for me to visualize....
Comment
-
It would have to be on a metal boat, cause glass would not carry currentComment
Comment