Routing of vst fuel lines

[marchmadness]

Sim Yamaha put out an instructional video"F225 Service Information VST Removal, Cleaning, Filter/Screen Replacement . I watched it and I was looking at frame 15 where it showed the routing of the fuel lines. How the lines are run is that correct? I am really talking about the cooler lines to the brass nipple on the VST. I tried to down load the picture but our site said it was to big.

[fairdeal]

I've seen those photos before
(IIRC that 'presentation' was done by a THT member)
but I never noticed that detail -

the hose with the steel 'El' is in a surprising location, right across the VST:





It actually looks pretty reasonable - but that is NOT the way it is routed on my F225TXRD :



nor in the Yamaha Service Manual:




my guess, that was not the first time that owner was removing the VST -
and on a prior occasion,
he re-assembled using a 'novel' placement of that hose

[marchmadness]

ok when I saw that , I thought oh %^&^%%^ mine is all wrong. But ok mine is routed correctly. But on that what does the fuel cooler do ? It cools unused fuel from the fuel rail?

[fairdeal]

what does the fuel cooler do ? It cools unused fuel from the fuel rail?

exactly.
Perhaps not needed, or much, at WOT -
but dropping down and idling after a hard run:

its hot under the cowling and the fuel isn't being consumed very fast,
that HP pump is just cycling it round and round....

[marchmadness]

That’s why it’s recommended to idle before shutting down. So if the vst is full no “cool” fuel enters the Vst .why isn’t all the fuel run through a fuel cooler?

[fairdeal]

Yamaha has done it different ways on different models -
some have the fuel cooler 'built-in' to the back of the VST itself

[pstephens46]

That’s why it’s recommended to idle before shutting down. So if the vst is full no “cool” fuel enters the Vst .why isn’t all the fuel run through a fuel cooler?

If VST is full then fuel system goes into “recirculate” mode and gets routed through cooler, no?

[99yam40]

I thought the VST pump only runs part time when idling.

but then when it does run the fuel has to go somewhere

[fairdeal]

This is for the F150
(with dual mechanical lift pumps; the OP's F225 has instead a single electric lift pump)





If there is a EFI Yamaha where 'the VST pump' does not run constantly with any engine rpm,
I am not aware of it.

[99yam40]

You are correct I messed on what pump turns off and on at idle.
Who know why my brain went in that direction?
I do not

[marchmadness]

It only appears that fuel from the rail goes through the cooler. When the relief valve opens the fuel goes in a loop. Putting it through the cooler would make sense but I don’t think it does

[boscoe99]

Fuel from the regulator to the fuel cooler then back to the VST.