gnc1017
Well-Known Member
This past summer, we had two instances where our motor had shut off without warning. Initially thinking our sending unit was bad and we were out of fuel (more on that later), we finally found that the tank was no longer venting due to a clogged vent fitting filter screen.
We have a side-fill cap fuel system with the tank in the center toon and a carbon canister. From the tank, there are 2 vent hoses (one towards front and one towards rear of tank) that are Y'd together to a common vent hose under our port rear lounger (we have a RCW - center walk-out). This common vent hose connects to a check-valve assembly with another hose then dropping down from there to a carbon canister. The other end of the carbon canister vents through the deck floor below. My understanding is that this system is very typical on these newer boats (ours is a 2015). All of this on our RCW is located under and just behind our port lounger backrest (that backrest just pulls off as it was held on by Velcro).
The end of our vent hose has a fitting that is screwed from above to the deck and flush with the deck on the underside. Once removed, this fitting has a small round black cap that screws off and a fine mesh screen just inside. Our vent screen was clogged with a residue (we're not sure exactly what yet - possibly evaporated fuel?), preventing the tank from venting properly.
What transpired during operation was that the fuel tank would suck inwards due to the inability to vent - so much that the fuel level and gauge would still read quite high (would read ~ 7/8 full and then drop to ~5/8 after vented by removing the fill cap). This suction also in-turn even caused the sides of the tank to bend our fuel sending unit rod (this happened twice until we figured out what was really happening). Initially thinking we were fighting a bad fuel sending unit (until our second one also bent) we finally realized it was the venting issue that was causing the motor to shut down.
I'm not sure if they still install the fine mesh screen in the end of the vent hose, but I'm curious if anyone else has this fine mesh vent screen and if so, if it is also clogged from some sort of residue. Most owners likely wouldn't realize it as our motor-shutdown issue only occurred after a full tank and then some lengthened run time. What we also now realize is that the amount of venting that comes through the fuel filler cap when we remove it is significantly less than it had been so thinking we have had this problem for a little while. So if you also experience a ton of air when you loosen your fill cap, you may want to check this component. If you check your system for a fine mesh vent screen, please post back your findings (does it exist and if so, is it clogged).
Here are some pictures of what we found. I've also posted the pics in my profile Media.
We have a side-fill cap fuel system with the tank in the center toon and a carbon canister. From the tank, there are 2 vent hoses (one towards front and one towards rear of tank) that are Y'd together to a common vent hose under our port rear lounger (we have a RCW - center walk-out). This common vent hose connects to a check-valve assembly with another hose then dropping down from there to a carbon canister. The other end of the carbon canister vents through the deck floor below. My understanding is that this system is very typical on these newer boats (ours is a 2015). All of this on our RCW is located under and just behind our port lounger backrest (that backrest just pulls off as it was held on by Velcro).
The end of our vent hose has a fitting that is screwed from above to the deck and flush with the deck on the underside. Once removed, this fitting has a small round black cap that screws off and a fine mesh screen just inside. Our vent screen was clogged with a residue (we're not sure exactly what yet - possibly evaporated fuel?), preventing the tank from venting properly.
What transpired during operation was that the fuel tank would suck inwards due to the inability to vent - so much that the fuel level and gauge would still read quite high (would read ~ 7/8 full and then drop to ~5/8 after vented by removing the fill cap). This suction also in-turn even caused the sides of the tank to bend our fuel sending unit rod (this happened twice until we figured out what was really happening). Initially thinking we were fighting a bad fuel sending unit (until our second one also bent) we finally realized it was the venting issue that was causing the motor to shut down.
I'm not sure if they still install the fine mesh screen in the end of the vent hose, but I'm curious if anyone else has this fine mesh vent screen and if so, if it is also clogged from some sort of residue. Most owners likely wouldn't realize it as our motor-shutdown issue only occurred after a full tank and then some lengthened run time. What we also now realize is that the amount of venting that comes through the fuel filler cap when we remove it is significantly less than it had been so thinking we have had this problem for a little while. So if you also experience a ton of air when you loosen your fill cap, you may want to check this component. If you check your system for a fine mesh vent screen, please post back your findings (does it exist and if so, is it clogged).
Here are some pictures of what we found. I've also posted the pics in my profile Media.