Fuel leak by

S

S.Robbins

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I have a 2017 Mercury 30HP EFI 4 Stroke, it sat for a couple of years without being started. I replaced the low-pressure fuel pump and high-pressure fuel pump components (electric pump, pump filter, needle valve, O-rings, fuel regulator) but have fuel leaking out the drain hose for the Air Vent Assy.
I'm at a loss as to why this is occurring, any assistance would be greatly appreciated
 

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Fun Times

Fun Times

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Hose number 26 goes from the VST to the air vent assembly,

From service manual part number 90-8M0105568 MARCH 2016 MERCURY 25/30 EFI SERVICE MANUAL section 3C, fuel system Service Procedures.
Remove the vent hose from the air vent assembly.
10. Connect the VST vent hose to the air vent assembly. Secure the VST vent hose to the air vent assembly with a spring clamp.... < Found online if needed.

Excess fuel out a vent generally means to much fuel flow is being delivered/pushed out by an item that has failed. So, you'll want to check fuel pressure... If pressure (both low and high?) is good then possibly either a fuel pump diagram is leaking (pin hole leak, bad gasket, etc.), the fuel regulator is compromised, the needle plus fuel float could be stuck or too high of a setting all escaping out the vent.

Was the fuel really old/bad/watered down of any sort when you had it all opened up?

Pull the vent hose line off at the regulator and see if fuel is spraying out form it too.

Hopefully you had and followed the service manual the first time around at replacing all those parts.

Is the entire area under the regulator clean from any rust or debris, etc.? anything under it or in flow of its return 'could cause high pressure.

What is your engine serial number to confirm using the correct parts catalog as this one was a guess to go by,
 
S

S.Robbins

Recruit
Joined
Jan 30, 2014
Messages
2
Fun Times said:
Hose number 26 goes from the VST to the air vent assembly,

From service manual part number 90-8M0105568 MARCH 2016 MERCURY 25/30 EFI SERVICE MANUAL section 3C, fuel system Service Procedures.
Remove the vent hose from the air vent assembly.
10. Connect the VST vent hose to the air vent assembly. Secure the VST vent hose to the air vent assembly with a spring clamp.... < Found online if needed.

Excess fuel out a vent generally means to much fuel flow is being delivered/pushed out by an item that has failed. So, you'll want to check fuel pressure... If pressure (both low and high?) is good then possibly either a fuel pump diagram is leaking (pin hole leak, bad gasket, etc.), the fuel regulator is compromised, the needle plus fuel float could be stuck or too high of a setting all escaping out the vent.

Was the fuel really old/bad/watered down of any sort when you had it all opened up?

Pull the vent hose line off at the regulator and see if fuel is spraying out form it too.

Hopefully you had and followed the service manual the first time around at replacing all those parts.

Is the entire area under the regulator clean from any rust or debris, etc.? anything under it or in flow of its return 'could cause high pressure.

What is your engine serial number to confirm using the correct parts catalog as this one was a guess to go by,
Click to expand...


FT,
thanks for responding.... see responses in italics

Was the fuel really old/bad/watered down of any sort when you had it all opened up?
Not varnished up but still old enough to smell old.

Pull the vent hose line off at the regulator and see if fuel is spraying out form it too.
No, fuel is not coming from Regulator overflow. I removed the lower cowling and it's definitely coming from the VST vent Hose.

Hopefully you had and followed the service manual the first time around at replacing all those parts.
No, but did allot of research prior to accomplishing repairs.

Is the entire area under the regulator clean from any rust or debris, etc.? anything under it or in flow of its return 'could cause high pressure.
Yes, no rust or debris, replaced both O-rings (5&6) of part 21 of the Hose, Fuel Regulator, including the regulator itself.

What is your engine serial number to confirm using the correct parts catalog as this one was a guess to go by
0R740079

As mentioned previously, all parts except the float have been replaced with new.
 
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