Figured this would help keep air out of the injector and subsequently out of the fuel system when I reinstall.
I fail to see the concern of air entering injector as this same injector contained air when it was brand new as will the injector lines.
If you have air in a mechanical fuel injection branch, the pressure from the injection pump is wasted compressing that air instead of opening the injector. Similar to having air in a hydraulic brake or clutch system. Having the injector full of diesel is essentially pre-bleeding that portion of the branch.
My thoughts are after injector is installed in cyl head and inj line attached to injector then when inj pump forces fuel through line to injector then line is tightened then loosened the trapped air in inj will be displaced by diesel then upon tightening line nut again there will be air free fuel in injector. Back when I was a JD dealer service manager when injectors were removed from cylinder head for engine overhaul or pop(pressure/spray) testing the injectors were not held upright to keep fuel in them. Nor do I ever remember reading in a tech manual that stated that this procedure was required or necessary.
Are you implying you think new injectors designated for parts are shipped from factory with fuel in them??
Thanks,Jim
Jim,
Yes - loosening the hard line tube nuts on the tops of the injectors and then cranking the engine (my manual says full throttle with decomp) seems to be a common air bleeding procedure. I'm saying that if you've just tested an injector that you're going to reinstall, you might as well leave the fuel in it so there's less air to bleed out of the system later. I don't think anyone is shipping injectors with fuel in them - probably against some shipping laws. I would imagine OEMs and rebuilders drain or purge them somehow after testing.
David
Any new injectors (24 of them) we install from Fairbanks-Morse for our diesel generator at work, and when testing the injectors ourselves, diesel fuel is not used to test the spray pattern and pop pressure. A non-flammable oil with similar properties is used so shipping with this fluid is not an issue.