Fuel filling problem

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BillyK

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Hello,

45' 1977 Chris Craft with twin 8v-71 diesels.

I put 100 gallons into a 250 gallon tank on the port side, no problem. When I tried to do the same to the starboard side it only took 30 gallons and pushed fuel back up the fill and forcefully out the vent. The tank is not full. Over the last week using jerry cans, I was able to put 30 more gallons into the tank with no problem. Today I tried to put 10 more in and it backed up and spilled out the fill and vent. The tank is still not full.

I removed the vent copper tube from the tank and snaked. It's possible there is some crud near the vent that stops air from venting, but not enough to stop fuel from spilling? What's going on? Anybody have the same problem?

Thanks,

Billy K.
 
A blocked vent is usually the problem filling the tanks.
 
I can think of only two thing. Mud wasps and spiders can build nests in the vent. Or the vent hose is collapsed. Snaking it may open it up for the snake to go past but collapse again when snake is removed.
 
If fuel is coming out the vent, how can it be clogged?
Jim
 
while not probably OEM, you may have a fuel/air separator on the vent line. this device is designed to allow air to vent while fueling and prevent fuel from overflowing thru the vent line. IF you have one, and it's stuck in the middle, it's: not letting air vent fully while fueling (thus, you can't fill the tank with 'full flow' at the fuel pump); and, it wouldn't stop fuel from overflowing thru the vent line.

$0.02.
 
Sounds like you are filling it and it takes a while to go somewhere.

How do you know it is not full?

Do you have cross connected tanks?
Do youe engines return fuel to opposite tanks?
 
This morning I removed the vent from the outside of the hull. It's copper tubing, not hose. I snaked it yesterday. There is no clog in the vent line. Crazy. Thanks for your thoughts.
Billy K.
 
The fact that the fuel comes out the vent is real weird. Everytime I v had vent issues the fuel would regurgitate from the filler not the vent. Irrelevant to your problem but a couple of years ago we had issues filling up a 15’ walker bay. Fuel coming out the filler. It turned out some new boats, even dinghies, have a filter on the vent to capture fumes... ended up having to follow the vent hose and discovered the offending tree hugging device hidden high up on the transom. Needless to say, it went into the closest trash bin !

In your case it’s not a vent issue.

I wonder if you don’t have a problem with baffles in the tank. If the holes in baffles are blocked for some reason, it could prevent fuel from flowing out beyond the first baffle fast enough. Long shot but I ve seen weirder things

How full is the tank? Can you use a stick to make the gauges are accurate ?
 
Hi,
The tank is half full at most. I hope your wrong about the baffles. That was one of my father's thoughts.
Billy K.
 
Can you transfer the fuel to the other tank (with diesel you can use a drill operated pump) and then stick a remote can in there? They re widely available And connect to your phone. What kind of tank do you have? Alum? Fiberglass? Good access to the top?
 
quote:
Originally posted by pdecat

Sounds like you are filling it and it takes a while to go somewhere.

How do you know it is not full?

Do you have cross connected tanks?
Do youe engines return fuel to opposite tanks?

Click to expand...

It's not even half full, I'm positive.
I have valves in the engine room. Each motor is independent and returns to the same tank.
Billy K.
 
quote:
Originally posted by PascalG

Can you transfer the fuel to the other tank (with diesel you can use a drill operated pump) and then stick a remote can in there? They re widely available And connect to your phone. What kind of tank do you have? Alum? Fiberglass? Good access to the top?

Click to expand...

It's a copper or bronze tank and I have a transfer system already set up. I have a camera too. I was hoping to not have to take it apart. Thanks for the tips.
Billy K.
 
Does the vent line have a constant slope of varying angle downward to the tank from the hull vent, or does it dip anywhere to trap fuel and go back up?

Will it take more at the pump if you pump at very slow rate? What diameter is the vent tubing? Common is 5/8"hose.

You checked the tubing . Is the vent fitting into the tank fully clear- i.e., no errant plastic film or some such blocking the air flow until filling tank pressure reaches a certain level when air pushes past the restriction and blows out any fuel in the vent line? OK, it's a stretch but you never know.
 
Hi Sandy,
It's copper tubing and I removed the vent at the hull. It's not the vent. I have to get into the tank as Pascal suggested with a flexible light. I can't understand what it could be that doesn't let air escape, but at a certain point belches fuel. After I get into the tank, I'll let you know.
Thanks,
Billy K.
 
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