Hi Troy,

I have found that bubbles in the injector line can mean a worn plunger in the pump, and its easy to test
if this is the case.

First remove the pump assembly from the engine complete with the two half push rods,
Get two pices of fuel tubing of sufficent length with a clunk attached to one end of each piece
and attach the other end of the tubing to the pump fittings.
Have two containers with some fuel in each container and drop the end with the clunk attached in each container.

Holding the pump assembly in one hand, and with the other hand hold the push rods between thumb and finger,
move the push rods up and down in the pump as fast as you can, the pump will start pumping fuel from one container to the other.
You may have to manually fill the lines and pump with fuel if it won't self prime.

While you are pumping fuel watch the fuel lines.
If the plunger is in good condition there will be no air bubbles in the fuel lines, if there are bubbles in the out side of the pump, then the plunger, and or, pump body is worn.
If you have bubbles on the in side to the pump then you have not set up the test properly.
I've found its usually only the plunger thats worn, and a new plunger is very cheap.

Reasemble the engine and test run, no bubbles in the injector line.

Team Crossman