342 fuel system

Black_Diamond

I know the top of my 342 fuel tank is about equal to the engine height or so, maybe lower. My fuel line runs down to the stringer then up to the pump/h2O filter..then to the injectors. So the delta from the bottom of the tank to the injectors is probably 'uphill'. Mine is a Merc set up, but the Volvo can't be off by much w/same fuel tank set up.

When I pulled my genset fuel line at the gen end the fuel in the line / filter got sucked back into the tank (shut off valve open) actually.

tkrfxr

Drew, I think you are right...a fuel shut-off solenoid valve is the way to go.....arguing with mfgs is pointless...

BD, I think the tanks are at least one foot above the engines when full...I will check whenI get the boat back....

212rowboat

if you look closely at the top of the image, and directly above the spring in the center top of the filter housing, there is a black disc.. that black disc is the anti-drain back device.. it is a flapper thingy.  This is the basic design of any spin on filter, though material and tolerances differ from brand to brand..  it is represented as item #2 on the image provided earlier.

the specific purpose of the flapper/diaphragm style valve is to disallow whatever fluid to drain back into it's source... in the case of oil, so there is oil available on start up.. in the case of fuel, so the prime happens and pumps aren't ran dry... I'm admitting they are designed to stop the flow in the opposite direction, and this may have been a player in the engine filling if in fact it was siphoned from the fuel source solely.  

I'm totally amazed that this is a possibility, and even more so that it actually happened.

tkrfxr

Drew, you are right, the anti-drain back mechanism does nothing to prevent forward flow...and as I have confirmed personally, gravity alone allows fuel to flow...which is how I remove the air from the lines and filter every time I change them...

tkrfxr

So the boat is back in the water, and the test run was awesome....

With the new fuel system overhaul, the engines pair up nicely, and power is clearly improved on both....

The mechanic is going to see if the tanks have the valves, and recommended shutting off the fuel lines manually until the issue is resolved.

I am leaning to have solenoid was installed regardless...