How do I depressurize fuel system on EFI Yamaha?

finkpat

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May 19, 2010
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Fellas,
What is the easiest way to depressurize the fuel system on a fuel injected Yamaha 4-stroke? The hoses feel tight, but I pressed on the schrader valve with a screw driver and nothing happened.

Thanks,
Patrick
 

rodbolt

Supreme Mariner
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Sep 1, 2003
Messages
20,066
Re: How do I depressurize fuel system on EFI Yamaha?

easiest way is to either pull the fuel pump fuse or unclip the high pressure pump connector and start the engine. when it dies your out of pressure.
 

finkpat

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May 19, 2010
Messages
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Re: How do I depressurize fuel system on EFI Yamaha?

Thanks for the reply....unfortunately, my engine won't start now, which is why I'm trying to depressurize so I can further investigate. Is there another method?
 

rodbolt

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Sep 1, 2003
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Re: How do I depressurize fuel system on EFI Yamaha?

yep.
post a model number.
yamaha makes EFI 4 strokes from 50 HP to 350 HP.
most likly the reason it wont start is LACK of pressure.
 

finkpat

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May 19, 2010
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Re: How do I depressurize fuel system on EFI Yamaha?

it's a T50TLR. you're right...there is no pressure in the system, even when flipping the key. 0 psi using a fuel pressure gauge. fuel pump just isn't working, but the fuse is good. i hear what sounds like a relay click on for 2-3 seconds and then off when i turn the key, but no pump noise.
 

rodbolt

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Sep 1, 2003
Messages
20,066
Re: How do I depressurize fuel system on EFI Yamaha?

to test the high pressure pump. unclip the pump connector, using a pair of jumper leads hook one pump terminal to ground and the other to battery positive.
if the pump runs test the main relay.
if the pump does not run.
remove the intake,remove the vst.
open up the VST and remove the high pressure pump. soak it in a jar filled with yamaha combustion chamber cleaner over night, retest.
 
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