Significant Fuel Consumption Difference

[bjd76]

It is a 4.2L manufactured in Dec 16.

[fairdeal]

Searching the forums, some past issues/suggestions for similar problem were:

- low pressure fuel pump problem and dumps gas in crank
- Leaking float valve (carbureted engine only?)
- Cracked pick up tube in fuel tank so sucks more air/gas
- Fuel injectors and/of VST filter clogged/issue

you can rule some of those out:
- low pressure fuel pump "dump gas in crank" is only possible when "mechanically" driven, yours are electric
- fuel tank pickup tube problem can only starve engine of fuel
- clogged VST filter limits rpms/power - not increase fuel consumption

but - your VST - vapor separator tank - has a float/needle valve (which can overflow)

[rodbolt17]

if the VST needle leaks you will see gas in the airbox/intake and the charcoal canister for the vapor recovery will be full and toast.
so that pretty much means if the ECU is adding more fuel to one engine and not the other for the same RPM you have an issue.

[bjd76]

Boat is a 2009 so I don't think there is a charcoal cannister involved? but given the fueling problem and the fuel consumption difference occurring at about the same time, I'm thinking the vapor separator tank and/or valve may have some bearing on this problem. I have tried to get my (master certified) mechanic to look into it with me but he has been too backed up on other projects. Changing spark plugs is a good first step but I don't think it will be that simple...

[pstephens46]

Boat is a 2009 so I don't think there is a charcoal cannister involved? but given the fueling problem and the fuel consumption difference occurring at about the same time, I'm thinking the vapor separator tank and/or valve may have some bearing on this problem. I have tried to get my (master certified) mechanic to look into it with me but he has been too backed up on other projects. Changing spark plugs is a good first step but I don't think it will be that simple...

That charcoal canister is an engine component not a boat part. I don’t have the pleasure of having one on my 2005 motor. Wonder if you could pull a few tubes loose to check for liquid fuel backing up in the system.