Service Manual

ISB, ISBe and QSB (Common Rail [...] Injector
Section 6 - Injectors and Fuel Lines - Group 06 Page 6-69
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Setup
Low Mount Fuel Drain Manifold
3.9L and 5.9L Engines Without EGR
These engines have a quick-disconnect fitting, with a
white tang in the fuel return port at the back of the cylinder
head.
Check for excessive flow in the injector return circuit due
to leakage.
Remove the quick-disconnect fuel line from the back of
the cylinder head and attach the fuel pressure gauge
adapter, Part Number 3164044.
Install the quick-disconnect block-off fitting, Part Number
3164583, on the drain line removed from the cylinder
head to prevent the back flow of fuel from the drain line.
Place the loose end of the fuel pressure gauge adapter
tool into a graduated cylinder, Part Number 3823705.