Fuel Tank Fitting - No Anti Siphon - Question

[Jacalore]

Working with a 1985 boat, the fuel line connection is thru a fitting directly into the top of the fuel tank. No anti-siphon device, no screen. Presently troubleshooting a fuel supply problem. I assume the connection is to an internal pipe directly to the bottom of the tank. How do you handle debris or old fuel crystals? Apparently, there is no filter, or screen or anti-siphon valve to clean? Any suggestions?
Thnx

 

[IllesheimVet]

Re: Fuel Tank Fitting - No Anti Siphon - Question

If your boat doesn't have one, I'd add a canister type fuel-water filter. I don't see the advantage of having a screen on the end of the fuel pick-up tube. Any sediment should get caught by the filter. If your fuel tank has chunks large enough to block the pick-up tube, the tank should be cleaned. IMO, it's better to have any sediment get caught in the canister filter, where it can be easily removed, than to get clogged up on a relatively inaccessible fuel pickup tube screen.

 

[dingbat]

Re: Fuel Tank Fitting - No Anti Siphon - Question

If your boat doesn't have one, I'd add a canister type fuel-water filter. I don't see the advantage of having a screen on the end of the fuel pick-up tube. Any sediment should get caught by the filter. If your fuel tank has chunks large enough to block the pick-up tube, the tank should be cleaned. IMO, it's better to have any sediment get caught in the canister filter, where it can be easily removed, than to get clogged up on a relatively inaccessible fuel pickup tube screen.

....+1

The anti-siphon is the thing I tore out and thru as far as I could when I bought the boat.

 

[Grub54891]

Re: Fuel Tank Fitting - No Anti Siphon - Question

The anti siphon valve is for safety,if a leak shows up when left unattended,it stops fuel from filling the bilge.Now imagine you are under way,a fuel line breaks,motor may or may not stop running,or run badly. Ya open the lid,see fuel leaking,try to find something to plug the line with,now ya got fuel on yourself,and all over the boat. Hmm...hot motor+fuel...... I'd vote for keeping the anti-siphon
Valve,inspecting the tank,and keeping it clean.
Grub

 

[Jacalore]

Re: Fuel Tank Fitting - No Anti Siphon - Question

The anti siphon valve is for safety,if a leak shows up when left unattended,it stops fuel from filling the bilge.Now imagine you are under way,a fuel line breaks,motor may or may not stop running,or run badly. Ya open the lid,see fuel leaking,try to find something to plug the line with,now ya got fuel on yourself,and all over the boat. Hmm...hot motor+fuel...... I'd vote for keeping the anti-siphon Valve,inspecting the tank,and keeping it clean.

I understand, and agree with, the safety purpose of the anti-siphon valve... just that my boat never had one, and I'm troubleshooting a fuel problem, so it's not at the top of my list presently. Thanks for the reminder, tho...

 

[louiefl]

Re: Fuel Tank Fitting - No Anti Siphon - Question

I would try running it on a small remote tank with a short piece of hose and fresh gas. If everything is ok, then it could be bad gas, plugged fuel tank vent line, weak fuel pump, plugged pickup screen, broken off pickup tube, collapsed fuel hose, air being sucked into a fuel line, etc. Otherwise the problem is at the engine.

I don't think they made ethanol resistant fuel lines in 1985, so I would be tempted to replace the line and primer bulb if you have one, and add a cartridge filter / water separator as suggested above.

 

[Home Cookin']

Re: Fuel Tank Fitting - No Anti Siphon - Question

I agree with Louie. bulbs can go bad but not seem to. anything along the line. If your tank bottom is funky try shortening the pick-up tube a little. I've seen them sit flat on the bottom of the tank with age and cause issues, too.

 

[metriccrescentwrench]

Re: Fuel Tank Fitting - No Anti Siphon - Question

I understand, and agree with, the safety purpose of the anti-siphon valve... just that my boat never had one......

It could be that one isn't required in your boat, it depends on the fuel system whether it's necessary or not. According to USCG regulations, an anti siphon valve isn't required if all fuel line is properly secured above the tank (in other words if the line sprung a leak it couldn't possibly siphon into your bilge).

And I agree with the comments about not putting a screen on the pickup tube and using a good filter. I like the filter/separators with a clear bowl which allows you to visually determine if you're getting crud in the filter, and to drain the filter bowl from time to time to get rid of any water etc.

 

[Jacalore]

Re: Fuel Tank Fitting - No Anti Siphon - Question

I would try running it on a small remote tank with a short piece of hose and fresh gas. If everything is ok, then it could be bad gas, plugged fuel tank vent line, weak fuel pump, plugged pickup screen, broken off pickup tube, collapsed fuel hose, air being sucked into a fuel line, etc. Otherwise the problem is at the engine.

I don't think they made ethanol resistant fuel lines in 1985, so I would be tempted to replace the line and primer bulb if you have one, and add a cartridge filter / water separator as suggested above.

Replaced all fuel lines and fittings from tank to carb, added inline fuel filter as well as changed the filters in both the fuel pump and carb. I will run it off a 5gal fresh fuel container to determine if the problem is before or after the engine pickup. Thanks.

 

[Jacalore]

Re: Fuel Tank Fitting - No Anti Siphon - Question

I agree with Louie. bulbs can go bad but not seem to. anything along the line. If your tank bottom is funky try shortening the pick-up tube a little. I've seen them sit flat on the bottom of the tank with age and cause issues, too.

The tank is built-in, under the floor and the pickup tube is welded inside the tank. No access. And, no bulb, this is an I/O. Thanks.

 

[Don S]

Re: Fuel Tank Fitting - No Anti Siphon - Question

The tank is built-in, under the floor and the pickup tube is welded inside the tank. No access. And, no bulb, this is an I/O. Thanks.

They don't make them like that. There is a thicker section welded onto the tank that has threads for the pickup tube that is screwed into the thicker base. They also have a screen on the end of the tube.

The anti-siphon screws into the hole on the top of the pickup. Here is a picture of a typical pickup tube.

 

[Jacalore]

Re: Fuel Tank Fitting - No Anti Siphon - Question

They don't make them like that. There is a thicker section welded onto the tank that has threads for the pickup tube that is screwed into the thicker base. They also have a screen on the end of the tube.

The anti-siphon screws into the hole on the top of the pickup. Here is a picture of a typical pickup tube.

Mine doesn't look like that, Don. There's a fitting at the tank, when removed there is no pickup tube... I assume what I'm looking at then is a pipe internal to the tank going from that top fitting to the bottom. Wrong assumption?

 

[Don S]

Re: Fuel Tank Fitting - No Anti Siphon - Question

Mine doesn't look like that, Don. There's a fitting at the tank, when removed there is no pickup tube... I assume what I'm looking at then is a pipe internal to the tank going from that top fitting to the bottom. Wrong assumption?

Then you must be looking at the vent fitting, because without that pickup tube, you are not going to be picking up fuel from the top of the tank.

Post some pictures, don't forget, we can't see what you can.

 

[Jacalore]

Re: Fuel Tank Fitting - No Anti Siphon - Question

Here's the fitting (before and after). Large hose is Fill and other side of that (out of pic) is Vent.
Removed the fitting and corroded old shutoff valve and replaced fuel line. No anti-siphon nor pickup tube/screen found.

 

[dingbat]

Re: Fuel Tank Fitting - No Anti Siphon - Question

Mine doesn't look like that, Don. There's a fitting at the tank, when removed there is no pickup tube... I assume what I'm looking at then is a pipe internal to the tank going from that top fitting to the bottom. Wrong assumption?

Mine is the same. It's an integral part of the tank.

 

[Jacalore]

Re: Fuel Tank Fitting - No Anti Siphon - Question

I would try running it on a small remote tank with a short piece of hose and fresh gas. If everything is ok, then it could be bad gas, plugged fuel tank vent line, weak fuel pump, plugged pickup screen, broken off pickup tube, collapsed fuel hose, air being sucked into a fuel line, etc. Otherwise the problem is at the engine.

Today ran engine until warm and idle ok. Still, any throttle and it stalls (original problem). In an effort to isolate the problem, I disconnected the fuel line at the fuel pump inlet and hooked up a line to a small exterior tank with fresh gas. Hoping to find out if the problem was before the engine or on the engine. Couldn't get it to idle. The engine would start after choking then race, and when I pulled the throttle back, it would die. Tried this numerous times.

Not what I expected to see... So, I reconnected the boat fuel supply back up to the fuel pump and same thing, hard to start - choke, race, die. I am not sure where to go from here. Any ideas?

 

[NYBo]

Re: Fuel Tank Fitting - No Anti Siphon - Question

Those are symptoms of a vacuum leak.

 

[Jacalore]

Re: Fuel Tank Fitting - No Anti Siphon - Question

You may be right, Bob. Took the boat over to the local garage. And the mechanic said he thought it was a fuel prob or air getting in... at least there will be someone looking at it that knows what they're doing. I'm done!

 

[Jacalore]

Re: Fuel Tank Fitting - No Anti Siphon - Question

Well, this was a mistake. Shop had it for a month, they replaced fuel pump and declared it fixed. I picked it up, went to the bay, launched and found same problem. No acceleration, stalls. To add insult to injury, when I picked it up, the key had been left on and the battery totally drained. I charged it, but it fails under load now (trim motor intermittent). So, I'm worse off then when I started.

I just ordered a few gauges and tools, I'm gonna get to the bottom of this yet!