stupid question

[James67]

When undertaking an air in diesel fuel line test using a clear inline tubing, how many micro bubbles is too many ? I have about 20 or so very small bubbles constantly flowing over a foot of clear tube when the engine is running. Also, when you prime the fuel line, how long should the plunger stay "hard" after stopping the prime and with the engine not running?

Thanks in advance, Jimmy

 

[Old.Tony]

It was my impression that the plunger should pretty much remain hard.

ANY bubbles spell a leak. If you're not actively leaking fuel, my guess is the leak is between the pump and the fuel tank, which could be anywhere from filter to tank but I'd concentrate around the filter, because that's the thing that gets played with during a service.