Early model:
• Cracked/broken check valve and fitting in high-pressure oil rail, under either valve cover(s).
• Disconnected high-pressure hose(s) under valve cover(s).
• Stand pipe from high-pressure hose to the branch tube in the tappet gallery (o-ring at the bottom could be cut/torn or missing).
Wavy rail:
• O-rings on the top and bottom of each stand pipe and/or all four plugs in the high-pressure rail.
All Models:
• O-ring in between discharge tube and high-pressure pump.
• O-ring around discharge tube that fits inside high-pressure pump cover.
• High-pressure pump inlet o-ring.
• Branch tube from high-pressure pump to stand pipe in the tappet gallery.
• High-pressure oil injector o-ring (high-pressure rail connects to the injector).