Air purging from the fuel system

[Flatlander]

I have a question about what the flow of fuel should look like when attempting to prime the fuel system.

First, I crack open the banjo bolt on the side of the secondary fuel filter while pumping the lift pump button. Then I crack open the 10mm bleeder bolt on the back of the IP pump and repeat the pumping. Fuel comes out of both, but it almost seems like air is coming out too. Kind of a "spitting."

Should this be continued until the fuel is coming out more smoothly, or is this "spitting" normal? I'm thinking there is probably a lot of air getting in, and that's what is causing this, but I've never done this before, so I don't know what it is supposed to look like.

Thank y'all!

 

[74M35A2]

If you only crack the banjo when pushing the primer, then it should be fluid only, like bleeding brakes on a car. If you are leaving the bleed screw open the entire time, it can suck air back in every time you are releasing the primer button. Yep, a lot harder to do it each time, but also more effective.

Honestly, once you have fuel of any sorts coming out of either, the truck should start right up. I have only had to do one or the other, and I have run out of fuel numerous times, all for dumb reasons. From there, if you are having running or full power delivery issues, be sure to replace your flexible lines on the suction side, and pull/inspect the pickup tube in the tank. Make sure fuel filters are clean and seated correctly and firm, any captive sealing washers positioned correct. These are known air intrusion points on these trucks.

 

[Flatlander]

If you only crack the banjo when pushing the primer, then it should be fluid only, like bleeding brakes on a car. If you are leaving the bleed screw open the entire time, it can suck air back in every time you are releasing the primer button. Yep, a lot harder to do it each time, but also more effective.

Do you also do this with the bleed screw on the back of the pump? I'm thinking that might be a two person job...

Honestly, once you have fuel of any sorts coming out of either, the truck should start right up. I have only had to do one or the other, and I have run out of fuel numerous times, all for dumb reasons. From there, if you are having running or full power delivery issues, be sure to replace your flexible lines on the suction side, and pull/inspect the pickup tube in the tank. Make sure fuel filters are clean and seated correctly and firm, any captive sealing washers positioned correct. These are known air intrusion points on these trucks.

I just ordered Ken Spencer's spin on filter kit, so hopefully that will fix any air that's getting in. I will also check the pickup tube. Thanks!

 

[74M35A2]

There is also an all stainless TIG welded tank pickup tube assy now available. Contact member TedCat if interested. Has a traditional male AN flare connection to it, versus the mil inverted flare, so best time to install it is during your flex line replacement. Requires tank removal for clearance to install.

 

[Flatlander]

Might have to replace that later. I have a full tank at the moment!