How to check for air in fuel lines on a Ford 6.9 & 7.3 IDI Diesel

This is a simple & cheap method to check for air leaks in your fuel system. Each fuel injector has a return line cap that is attached with 2 o-rings, and over time these can either leak fuel or suck air....both will cause your truck to run very rough.
This same method can be used on 6.9 & 7.3 IDI trucks/vans.
The parts you will need are only 2 different sizes of standard clear vinyl tubing from your nearest hardware store. The sizes are :
7/16" OD x 5/16 ID --- approx 2 feet
3/8" OD x 1/4 ID --- approx 3 feet
If you have any questions, please let me know!
Thanks