Air in Diesel Fuel System

[michaelmrc]

Good day alll and happy new year
Came across the Georgia strait a few days ago to spend new years in false creek engine (yanmar1gm10) was running great right up until I got into burrard inlet then it started running a little rough while the engine was running I cracked the injector pump bleed screw slightly the engine smooths out and revs up making me think I'm getting air in the line so this morning I bled the system andseemed like their was a little air so now I'm heeding back the engine won't reach max rpm and is surging was almost thinking maybe the lift pump has a pinhole causing air to enter any thoughts and is there any way to test a lift pump any other suggestions thanks everyone

[r.furborough]

Before doing that make sure your primary and secondary fuel filters are clean, it sounds like you may have a partial blockage leading to a lean fuel mixture, this can lead to an increase and surging of RPM's. If are blocked, check fuel in tank and pickup in tank.

[Badsanta]

YES, check your filters first

[DeepFrz]

And check your fuel line to make sure it isn't plugged. Because it ran well for most of the trip maybe you have a pinhole in your pickup tube that didn't reveal itself until the fuel level in the tank dropped. Also check that you don't have a screen on the bottom of the pickup tube.

[michaelmrc]

I do have screen on the bottom of the pickup tube should into have this?

[David M]

Air in your fuel system is a sign of a vacuum leak between your fuel pump and your fuel tank. It could also be air in your your fuel system from it not being bled thoroughly when you last changed out a filter. Check all the work you have done in the recent past.

If you cannot find the leak then you will need to put a slight pressure on the system and look and listen for fuel or air leaking out.

[DRS]

Check all the clamps and hose fittings at the filter heads as well. I had a situation on my gen set with air entering via the connection at the aux. fuel pump fitting. Have you replaced any of the filters recently?

[perchance]

Originally Posted by michaelmrc

I do have screen on the bottom of the pickup tube should into have this?

I don't believe it is common practice to have a suction strainer on the fuel pickup line in the tank. Most tanks are difficult to access and a plugged fuel strainer could be a recipe for disaster.

[David M]

Air in the fuel is caused by an air leak or insufficient bleeding, not a blockage. Or it's caused by an almost empty tank that sometimes is providing fuel and sometimes air.

[sailvayu]

That screen at the bottom of the pickup tube is a pain in the ass to keep clean. Use a good quality primary filter like a racor and get ride of the screen. other than that just check all your fittings for leaks.

[John A]

Whenever I had air in the injector pump, from an air leak, the motor would race for a few seconds simular to running out of fuel, and then quit.
What the OP has sounds like fuel starvation, caused by a clogged fuel delivery system.

[DeepFrz]

Definitely get rid of that strainer on the pickup tube. That thing will bite you where you don't want to get bitten. When you have the fuel pickup tube out of the tank inspect it very carefully for kinks or corrosion and make sure there are no pin holes in it.

[michaelmrc]

Ok will remove the screen and change all fuel lines going to the pump
Now I'm familiar an comfortable with bleeding the engine but not fully understanding the procedure for bleeding the filter thanks for everyones advise

[michaelmrc]

so what is the proper procedure for bleeding a new filter. or when i change the fuel lines from the tank to the filter . thanks

[John A]

Originally Posted by michaelmrc

so what is the proper procedure for bleeding a new filter. or when i change the fuel lines from the tank to the filter . thanks

You don't "bleed" the filter, you change it.
If you have two filters on the fuel line, disassemble your primary filter, usually a Racor, and clean it too.
Put everything back together and then bleed all air from the fuel line and you should be good to go.