Fuel Leak

[RV4]

Hello All
I have a fuel leak on my 2009 Mercury 25 HP EFI and I'm trying to find a cure to it..
The fuel leak at the bottom ( Midway)of the fairing of the engine and is coming from the Air Vent Assy..
I just installed a new Vent Assy thinking it might be it but it didn't fix the problem..

Is there anyone here who might have a solution to this problem??

Thanks

 

[alldodge]

Fuel leaks come from pumps, rails, injectors and lines. Look at those components and their location to the leak

 

[RV4]

Thank you for the reply
I checked all those and all are good.
The fuel is dumped overboard via the Air Vent Assy which has been replaced to no effect.
I have a fuel regulator on order hoping it might be the problem, if not my other option is to remove the float and needle, clean or replace them if need be and see if it fix the leak…
Am I right on this???

 

[alldodge]

what is the motor serial number?

 

[RV4]

SER: OR320978
2009 25HP EFI

 

[alldodge]

I think what your seeing is coming from the VST. In link below note the fitting on top left of the tank cover. This should have a tygon tube connected and going somewhere. When you see fuel see if fuel is in the tube

https://www.mercruiserparts.com/bam/subassembly/32557/11848/95

 

[racerone]

Cleaning / inspecting the float and float valve is a good step to take.----Float might be full of gas ??-----There is no way that I would want a motor like that.----I looked at price and availability of parts.--------Things like an ECU have been superceded and listed as NLA.---They run really nice.-----But no thanks.-----Give me and old motor as I make them run really nice.

 

[RV4]

That is what I think also.It is definitly coming from the VST but what is causing it to dump fuel overboard??

If I'm right on this, there are only 2 component in the VST that could be the culprit..Either the fuel regulator not doing its job or a sticky float/needle allowing too much fuel in the VST which is eventually dump overboard via the Vent Assy...
Does that make sense to you??

This is all new to me as I used to work mostly on aviation engine in a previous life ( Jet and recipe ) which I thought were complicated

Thank you for your help, I appreciate it.

 

[RV4]

Cleaning / inspecting the float and float valve is a good step to take.----Float might be full of gas ??-----There is no way that I would want a motor like that.----I looked at price and availability of parts.--------Things like an ECU have been superceded and listed as NLA.---They run really nice.-----But no thanks.-----Give me and old motor as I make them run really nice.

---------------------------------
Cleaning / inspecting the float and float valve is a good step to take.----Float might be full of gas

That is my next step, open the VST and clean everything in there...

Hoping it will fix the problem..

 

[alldodge]

The Regulator might but only if its blown and then it would do it all the time. The needle and needle seat is the weak link and has greatest possibility of causing the problem. It might be the float but these days IMO it doesn't happen very often and like the regulator it wouldn't work and not work, then work again.

 

[Fun Times]

If possible, with the engine running, pull the vacuum hose off the fuel pressure regulator and see if there is fuel coming out the vent line area of the regulator as there shouldn’t be but it’s sort of a common problem when the fuel pressure regulator diaphragm goes bad internally… Even on cars.

 

[RV4]

If possible, with the engine running, pull the vacuum hose off the fuel pressure regulator and see if there is fuel coming out the vent line area of the regulator as there shouldn’t be but it’s sort of a common problem when the fuel pressure regulator diaphragm goes bad internally… Even on cars.

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It will be kind of hard to pull the vacuum hose off the fuel regulator as it is part of the VST and hard to access ..
I've got a new regulator of its way which should be here in the next few days so I'm hoping it will fix the problem.

Yesterday I opened up the VST and looked at everything ( Float & needle ) cleaned everything ( There wasn't any dirts of any kind) the float looked good to me with no apparent flaw..

 

[QBhoy]

Hi. Is it leaking all the time or is it perhaps leaking and venting because someone has fitted a primer bulb in the fuel line and you might be pumping it before starting? Generally shouldn’t be a primer fitted on newer efi engines. Or if there is one from a previous older engine…it shouldn’t be used with the newer.

 

[RV4]

Hi. Is it leaking all the time or is it perhaps leaking and venting because someone has fitted a primer bulb in the fuel line and you might be pumping it before starting? Generally shouldn’t be a primer fitted on newer efi engines. Or if there is one from a previous older engine…it shouldn’t be used with the newer.

QBhoy:
Yes there is a primer bulb in the fuel line but it has been there for years without causing any problems so I will be surprised if it is causing the problem.. Also once the engine is started the primer bulb is out of the loop
Yesterday I found the VST fuel drain hose with a crack in it and as you know ii is running down the engine beside the air vent hose so I’m thinking that it might be the cause of the leak… Fuel dripping down the vent line making me believe that is where the leak is coming from when it doesn’t..
The fuel line has been replace so I should find out once I get everything back together..
I will let you guys know..

I do appreciate your inputs ..