Air lock in fuel line ????

Crazy Horse · Apr 10, 2016

When my tractor sits for a few days, it seems to have difficulty starting. It will start sporatically and run for a while on and off using the choke, but even that comes to an end. If I crack the fuel line at the in-line filter, a few bubbles escape and then after I hook things up again, the tractor starts well and runs well. Somehow I suspect maybe an airlock is occurring in the fuel line. Any idea why this might be happening? I can almost see myself putting some sort of a bleed valve in the fuel line to make all of this easier, but that isn't my first choice. It's a Massey Harris 20 with a Continental flathead engine. I've had numerous tractors with this same engine and have never encountered this issue before.

dpendzic · Apr 10, 2016

sounds more like a fuel line leak letting air in

Rollie NE PA · Apr 10, 2016

I have always been told to never use a inline filter on a updraft carb. I have never tried using a inline filter so I can't say one way or another but I don't know if any tractor ever came from the factory with one.

Janicholson · Apr 10, 2016

A NAPA filter used with gravity feed (available) will solve it in my opinion. Jim

Bob Harvey · Apr 10, 2016

How about opening the drain plug on the fuel bowl (carb) before you start. You can replace the 'nut' with a rad drain. Might tell you something. HTH

Traditional Farmer · Apr 10, 2016

I use them all time with no problem,beats having something in the needle valve.

Steve@Advance · Apr 10, 2016

I would start by taking the fuel valve/strainer/separator valve out of the tank and giving it a good cleaning. If there are rust flakes swimming around, dump and rinse the tank.

The fuel line needs to be steel, not copper, and routed the most direct, down hill, and as far from the ex manifold as practical. I think this uses 5/16" tubing, the same as the premade brake lines from the auto supply.

There may also be a screen in the inlet fitting of the carb, if so pull it and clean it. Be sure the screen is in the top of the separator and in good condition. Between the 2 screens, there should be no need for an inline filter. Be sure the gas cap is vented. Even if it says "vented", verify that it really is, sometimes they are not, or the vent is plugged.

Finally, you may want to open the carb, make sure every thing is clean and the float level and drop are correct. Be sure the needle is not sticking in the seat, sometimes they do for mysterious reasons, may be mechanically sticking from a worn rubber tip, or from evaporating ethanol.

showcrop · Apr 10, 2016

Vapor lock or air lock is the suspected culprit probably twenty times more than it really is. One thing that you can count on is that it takes heat to make the vapor and your cold engine isn't going to supply this heat. Your problem is an obstructed fuel supply.

flying belgian · Apr 10, 2016

Did you check the vent hole in the gas cap? Sometimes it is as simple as that.

Pete in MD · Apr 10, 2016

Do away with the in-line filter temporarily or put in a new one and see what happens.

David G · Apr 10, 2016

Give the carburetor a rap with a wrench, see if it works any better.

Dalex · Apr 10, 2016

All 6 of my tractors have inline filters , wouldn't run without them .

T in NE · Apr 11, 2016

Yup. If the line is sealed there will be no air in the line.

Try trimming the rubber line back just a touch or replacing it if it's old and hardened.

Air lock in fuel line ????

Crazy Horse

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dpendzic

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Rollie NE PA

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Janicholson

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Bob Harvey

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Traditional Farmer

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Steve@Advance

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showcrop

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flying belgian

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Pete in MD

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David G

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Dalex

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T in NE

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