Fuel tanks

[seahouse]

Note that the "M"and "X"fuel compartments have different dimensions...

[Boblee]

Aha perhaps thats the problem.

[hschumac]

With the positive statements here about the size of the Neptune 6 gallon tank (you can fit 2 in each locker) I bought one to replace an old tank that was leaking.

Since I have been using it, constantly cursing it.

Major problem with venting. I open the vent, connect the fuel line, prime the bulb, and after the engine runs for a minute or two and empties the hose, motor dies. It is unable to pull any fuel from the tank.

Last weekend on a long cruise was having the problem, guessed that it was the vent in the fuel cap. Swapping over the cap on my existing older style seemed to make it work. In fact, today is worked for an hour or so ago. Then after stopping over at a dock, headed out again and the motor could not pull any fuel. Even the primer bulb couldn't fill up.

Anyone have a similar issue, either with the Neptune specifically or another?

I thought I would just replace the cap, but now not sure what is going on.

[seahouse]

Check for leaks in the hose between and including the bulb and the tank. Check all connections made in the hose, including the quick-connector o-rings at the tank. If air were leaking in (the area of the line is under suction) at some point, it would give the symptoms you describe.

Just fixed a dock neighbour's issue with this this week. His hose clamps were too large, and not placed properly in relation to the barbs on the fittings being clamped, so air was getting sucked in. After overhearing him working on it for an hour or so I did a friendly stroll over and we had it diagnosed, repaired, and running like a top in 10 minutes.

Hopefully yours will be as simple.

- Brian.

[tlgibson97]

When I was having fuel feed issues it ended up being the fuel pump diaphragm. I still run E10 gas so it plays havoc on the fuel system of my old engine.

Does anyone have any solution to the venting issues on these new tanks? I have two 12 gal tanks installed and if they aren't completely full they will swell up so much that the cap contacts the access port in the seat to where I cant get the access port cap off. Once I get that cap off, there is so much pressure it's difficult to take the tank cap off. The only solution I have found is to leave the fuel cap loose a bit. If it is that difficult for the caps to relieve pressure I have no idea how easy it is for air to get into the tank while running the engine.

[RobertB]

The new fuel tanks have a cap that prevents normal venting. You can loosen the valve knob on the top of the cap, but in my case, the seat will not lower fully over the tank because of this knob sticking up. Another solution, one I used (and recommended by Moeller), is to use a replacement cap that is for the older style.

[hschumac]

There is no issue with the fuel line hose. Works great with my old tank. Connected to new tank if I pump the bulb the bulb compresses fully (implodes) on itself. If there were an air leak issue I expect that I would continue to be able to compress the bulb, only it would be filled with air. I cannot suck in anything (fuel or air).

I thought that putting the old style cap (from my other old tank) had fixed it. Have had some luck doing that. But yesterday even that didn't solve it. Even with the cap completely off I couldn't pull any fuel into the hose.

Potential issue with pickup within tank? Or the exit valve?