Rawze.com: Rawze's ISX Technical Discussion and more

Just trying to understand exactly what's involved in troubleshooting the high pressure fuel system if it won't pass the insite leakdown test.

First thing would be replace the banjo bolt that holds the relief valve on the end of the rail with a solid bolt and re run the leakdown test. If it now passes, the relief is bad.

If it still does not pass, you then cap off an injector with the cummins caps that are made for this purpose. Start the truck and run it on 5 cylinder's re run the leakdown test. If it passes that means the injector you capped off is bad.

If it still won't pass do you hook that injector back up to the rail and cap off the next one and repeat the leakdown test and keep going down the rail like that?

In this thread Mr hagg says he has all 6 caps so he can cap off as many injectors as needed, if you capped off all 6 injectors how would you be able to run the leakdown test? And you couldn't possibly have 6 bad injectors anyway.

http://rawze.com/forums/showthread.php?tid=6588

What am I missing here?

You forgot the step where you re-torque all the quill tubes (injector feed-tubes) at the head before resorting to accusing injectors being bad.

I think Mr.Hag will block off 1 then keep going till he gets to up to 3 or 4 at a time ... measuring the leak rate each time to see if it changes how fast or slow it leaks down. If the leak rate slows way down, even if it is still failing, then you likely have a bad one capped off.

the truck will start and run on a minimum of two injectors I found when I was trying to figure mine out. I didn't try just one but it might be possible I'm not sure if that helps you any