Air in Generator Fuel Line

November 10, 2016, 04:41:55 pm

I have a generator problem that has stumped me for some time, hopefully someone can point me toward a solution. I have searched the archives but not found a solution there for this specific situation. I am definitely getting air in the fuel line but have not located the source.

When I start my generator it will run for a minute then stumble and die. I then bleed the system by cracking one of the banjo fittings or, more recently, removing the return line to bleed into a container. With the system open, I run the electric fuel pump and it spits and sputters an air/fuel mixture for most of a minute before running pure fuel. Then closing the system I can start the generator and it will run beautifully for hours on end. If I then shut it down and wait for half an hour or so it will restart and run normally. If, however, I let it sit for several hours or over night until the Isuzu engine has cooled down, it will start, run for about a minute then stumble and die. Then I repeat the process.

Those are the symptoms. I have replaced all the supply and return lines (and clamps) in the generator compartment. I have not yet replaced the lines from the generator compartment to the fuel tank. Once I started bleeding the system into a small container so that I did not slop fuel all over the engine during bleeding, I have detected no fuel leakage around the generator compartment either while it is running or after it has been sitting.

The curious thing for me is that the engine would run so well once bled but gets so much air in the supply line while it is shut down.

If anyone has had this problem or knows where I should look for the problem, I would be grateful for any help.

Thanks,

Richard

Re: Air in Generator Fuel Line

Reply #1 – November 10, 2016, 04:46:41 pm

I had a leak in the fuel line. I had to replace the line. It was breaking because it had hardened up from age.

Re: Air in Generator Fuel Line

Reply #2 – November 10, 2016, 06:38:28 pm

The symptoms possibly indicate a very slow leak of air into the the fuel line upstream from the generator. The generator will run for a short time on the fuel in the line until the air bubble reaches the fuel pump. Once you bleed the system, the air leak is small enough to not interrupt fuel flow to the generator. I would check (replace) that fuel line from the generator compartment to the fuel tank. If the rest of your fuel lines are original, they are about at that age when they begin to harden and crack.

Re: Air in Generator Fuel Line

Reply #3 – November 10, 2016, 07:27:20 pm

I would remove both ends of the fuel line, block one end of the line and on the on the other end put a gauge and a shrader valve using a tee and put 20 lbs of air in it and see if it holds.

Re: Air in Generator Fuel Line

Reply #4 – November 10, 2016, 07:39:18 pm

How about the primary fuel filter leaking air?

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