Fuel Tank Issue

[TMANN]

It's not that hard to confirm which setting of fuel valves are or are not getting fuel thru the filters. Just doit and know what is going on. Could be air leaks, bad primer bulb, low fuel in filter can. Work backwards from there.

With all due respect its bad advice. Telling an individual who may not be very mechanically inclined to break filter and bulb connections just increases the possibilty to introduce more problems.

Those components are flowing fuel already.

The engine lines, primer bulbs, flow meters, seperating filters, fuel selector blocks, fuel lines to the tanks, anti siphon valves, and pickups are all redundant.

Multiple failures are possible, but not probable.

 

[Hookup1]

So what does "air locked" mean? I'm trying to make this understandable. What's wrong with making sure you have or don't have fuel to the engine depending on valve settings? If you can't prime them find out why. Don't guess.

My bet is fuel filters are not full. Or primer bulbs are bad. Maybe no fuel in the main tank or boat pitched down at bow. Start there. It's not that complicated unless you make it so. Start there. We'll see.

 

[Legend]

It is the Main tank that isn't getting fuel. The Aux tank is fine. I don't think the vent is blocked because I filled the tank up too high, and gas was spitting out of the gap and to be best of my knowledge the vent is under the cap.

i would set both valves to the main tank get the engines running
and after 15=20 minutes shift the auxiliary tank off and see if the ehgine stays running. It may be some type of air lock.

 

[Throttle1971]

My first test to diagnose is to start it up and turn both valves to the Main tank. If engines die then the issue is likely at the valve back towards the Main tank. Next, I will remove the fuel line from the main tank AT THE valve and see if gas is flowing. Need to be cautions with spillage because the gas will flow by gravity. Next test would be to swap the ciphens but I don’t think the issue is past the valves. Thoughts?

 

[kirk a]

If both engines die, it would point towards a venting type of issue, as there are two separate fuel lines running between the tank and valves. If only one engine dies, it could be a fuel line kink or other blockage in that particular combination of lines and valves. The odds of both valves going bad simultaneously are probably astronomically low, given the redundancy of the system.

When did the motors last work correctly on the main tank, and what has been done since that time?

 

[Finest Kind]

It is the Main tank that isn't getting fuel. The Aux tank is fine. I don't think the vent is blocked because I filled the tank up too high, and gas was spitting out of the gap and to be best of my knowledge the vent is under the cap.

Hmm...sounds like there might still be enough gas up in the fill tube that is blocking the vent.
Try removing the fill cap on the main, insert a siphon hose and remove a gallon of gas.
(just pour it back into the aux)

That may eliminate the vent blockage stopping main tank fuel flow?

 

[Throttle1971]

Hmm...sounds like there might still be enough gas up in the fill tube that is blocking the vent.
Try removing the fill cap on the main, insert a siphon hose and remove a gallon of gas.
(just pour it back into the aux)

That may eliminate the vent blockage stopping main tank fuel flow?

Good advise! I will reply back once I fix the issue.

 

[Hookup1]

I’m not convinced it’s an overfill/vent issue. That Perko fuel fill with vent is up high- within 3” of the cap. Leave cap loose to test. Check o-rings are good while you are up there.

You lost prime on the main tank. Main tank hoses from pickups to tank valves have air in them. You not creating enough vacuum with primer bulbs to get the air out..

Do the primer bulbs pump up hard when you switch to main tank? If not it may be time to replace them. Check that both the filter cans and the engine filters are full of fuel and pump a lot. Removing engine side hose from primer bulb makes it easier to clear air trapped in fuel lines.

 

[Roho]

May or may not be the case with your problem but if you run out of gas on either tank it will suck all fuel from filters etc. and neither will run until you change tanks and refill filters. If not, call seatow or U.S. don’t ask how I know!

 

[Hookup1]

May or may not be the case with your problem but if you run out of gas on either tank it will suck all fuel from filters etc. and neither will run until you change tanks and refill filters. If not, call seatow or U.S. don’t ask how I know!

Very difficult to fill filters with primer bulb (don't ask me how I know either). Pumping air with primer bulb is very inefficient. Once you get liquid they work so much better.

Diesel boats I work with have fuel circuits that return unused fuel to the tank. The primer pumps don't have to fight fuel back pressure and can clear all the air. We always topped off the main and Raycor filters before priming. Gas boats don't work that way so it's harder to get the air out.

Legend's post #23 suggested an alternative way to get air out of lines. I've done this too and it works well. Get the engines running on the Aux tank (Aux position - not both position). Then switch to Main tank and push the RPM's up. You need to burn up enough fuel to bring the air in the hoses up into the filter.

 

[kirk a]

Any further update?

 

[SkunkBoat]

As promised pictures below of the fuel valves and fuel Seperators. The valve on the left is for the Aux tank and the valve on the right is for the Main tank. Would you agree that the position of the valves below is only going to get gas from the Aux tank?

Are you sure about this statement?
The Grady setups that I have seen, the left valve is for the Starboard motor. The right valve is for the port motor. They choose which tank the motors run on.
The outside hoses go to different tanks and center goes to one motor.

If it were the other way, you would only have one tank per valve. That changes everything that has been said.

 

[Roho]

Not on my 2005 Gulfstream as it has the main and auxiliary, gas up both tanks. Be sure to switch tanks before either tank runs completely out, if not you must remove filters and refill as bulbs will not refill filters.

 

[kirk a]

Are you sure about this statement?
The Grady setups that I have seen, the left valve is for the Starboard motor. The right valve is for the port motor. They choose which tank the motors run on.
The outside hoses go to different tanks and center goes to one motor.

If it were the other way, you would only have one tank per valve. That changes everything that has been said.

I called this out earlier - I believe his interpretation of the hose configuration is incorrect. Your comment aligns with that as well.

 

[SkunkBoat]

Not on my 2005 Gulfstream as it has the main and auxiliary, gas up both tanks. Be sure to switch tanks before either tank runs completely out, if not you must remove filters and refill as bulbs will not refill filters.

Huh?

 

[Roho]

Exactly

 

[Finest Kind]

"huh?" ..."exactly"...LOL!

Skunk is correct. There are two valves that determine which tank the fuel is being drawn FROM to run each motor.

Poiny end of the valve handle towards stern is AUX.
Pointy end towards bow is MAIN.
(on my boat)

BOTH towards stern = both motors running off AUX
BOTH towards bow = both motors running off MAIN

Of course if you need to, you can run one motor off AUX and one off MAIN as well.

 

[Roho]

"huh?" ..."exactly"...LOL!

Skunk is correct. There are two valves that determine which tank the fuel is being drawn FROM to run each motor.

Poiny end of the valve handle towards stern is AUX.
Pointy end towards bow is MAIN.
(on my boat)

BOTH towards stern = both motors running off AUX
BOTH towards bow = both motors running off MAIN

Of course if you need to, you can run one motor off AUX and one off MAIN as well.

 

[Roho]

If you think I’m arguing, you’re wrong. I said MY boat. I speak from my experience, you speak from yours. Blessings!

 

[Hookup1]

There valves on my 268 Islander are set to MAIN (pointing to starboard side). There is a rumor that the center position, red end marked to bow, is a BOTH position. Maybe but I wouldn't trust it. Setting valve indicators to the other side are for AUX.

Left valve on port side is for port motor. Right valve on the starboard side is for starboard motor.

Are your valves mounted side-to-side like mine OR bow-to-stern?