Air in fuel lines?

[newbie4life]

Hi guys,

I'm still struggling with my 1984 Yamaha 40 ELN.

Well, after doing some carb cleaning again, boat started right up, ran perfect on the muffs -- put it in the lake, started hard, worked hard to keep it running -- didn't get full rpms. Pulled the hood off, and I see all kinds of air bubbles in the clear fuel lines. While I'm not the sharpest knife in the drawer, this doesn't seem right. So, the troubleshooting starts again.

Doesn't seem like the bulb pumps up hard -- replaced it (again). Pulled the gas line off the fuel filter, pumped into a cup, to get the air out of the fuel lines -- reconnected to the fuel filter, seems like it pumped the air out this time. Let it sit for a few minutes, and there's bubbles in the clear lines under the engine cover again. I've replaced both 'ends' on the gas line that goes from the tank to the engine -- what normally goes on these things, the tank fitting, engine fittings? Do the male fittings on the gas tank ever get worn enough that they need replacing? They are both steel tanks, which don't allow for simple changing of the fitting -- seems like it's an 'all-in-one' piece.

Would a perforated fuel pump cause this? Maybe even a slight tear?

I appreciate any help you can give me,

Thanks,

Jason

 

[mphelle8vld]

Re: Air in fuel lines?

Remove the 2 mounting bolts on the fuel pump and pull it away from the block, pump up the bulb, if fuel dribbles out the back of the pump you need to rebuild it.

 

[newbie4life]

Re: Air in fuel lines?

Remove the 2 mounting bolts on the fuel pump and pull it away from the block, pump up the bulb, if fuel dribbles out the back of the pump you need to rebuild it.

Well, I did just that -- while I'd get a drip out of the fuel pump every so often -- when I pumped up the bulb... I see one of those little freakin' zip ties on the back side of the filter housing leaking little tiny bubbles in to my gas line. couldn't see it on the front -- but on the back side it did.

Going to the automotive store to get clamps instead of zip ties -- I know mechanics are using them left and right -- but I'm not impressed with them so far.

We'll see what that does.

 

[mphelle8vld]

Re: Air in fuel lines?

Replace with proper clamps and hose, I don't think that clear vinyl tubing is rated for the heat under the hood. If you have ANY fuel coming out of the back of the pump, the diaphram has a hole. The power pulse of the piston will shoot air through the backside of the diaphram and into the fuel line.

 

[99yam40]

Re: Air in fuel lines?

If you get fuel leaking out anywhere on the suction side of fuel pump it will be sucking air in at those points while pump is operating

 

[newbie4life]

Re: Air in fuel lines?

Replace with proper clamps and hose, I don't think that clear vinyl tubing is rated for the heat under the hood. If you have ANY fuel coming out of the back of the pump, the diaphram has a hole. The power pulse of the piston will shoot air through the backside of the diaphram and into the fuel line.

Huh -- I'm not sure what to think here -- the clear fuel line... is fuel line. Is this not rated for the under hood temps of a two-stroke? I'm grateful for the clear line, since it helped figure out my issues...

Once I replaced those stupid zip ties with regular clamps, the sucker works like it should in the driveway - and after sitting for an hour, it hasn't allowed air into the fuel lines. Glad that's finally done...

But the fuel line thing worries me a bit -- While it is fuel line, rated for fuel -- perhaps I need to change it out if the temps are too warm for it? It's only a few feet that I would need, but... it's a pain to get at some of those stupid fittings. If the clear vinyl isn't rated for heat, then, I better for safety's sake. Anyone else have any knowledge on the clear line?

Thanks for all the help,

Jason

 

[99yam40]

Re: Air in fuel lines?

Only clear fuel lines I have seen were on chainsaws and weed eaters and they never lasted long before falling apart.

I would not want a fuel leak on a boat, no place to go to get away from a fire but jump overboard

 

[mphelle8vld]

Re: Air in fuel lines?

Ditto. Lot's of people use clear tubing to troubleshoot a fuel issue, I just don't know anyone who leaves it under the hood permanately. Here's an old thread that talks about fuel line: http://forums.iboats.com/showthread.php?t=355524

Hopefully the hose clamps fix your issue, I would order the $20 fuel pump repair kit as insurance.

 

[newbie4life]

Re: Air in fuel lines?

10-4.

Replacing the fuel lines this afternoon.

Thanks for the opinions,

Jason