It sounds like your UVCH (Under Valve Cover Harness) is loose or possibly shorted out on one side. Search for "UVCH" and you'll find LOTS of information.

EDIT: PaysonPSD posted this in another thread and has links with details.

Some info about UVCH.

What your problem might be. LINK

How to OHM out the UVCH for continuity:

Checking the ohms reading at the valve cover connector on the outside.

Pin Out

G
G
I
I
C
I
I
G
G

G=Glow Plug
I = Injector
C= Injector Common

NOTE: The injectors fire with a 115VDC signal from the IDM. *** Do Not pierce the wires to test***

Test between "I" and "C" to test the injectors, should be less than 5.0 Ohms.

To check glow plugs Test between "G" and battery ground. Should be between 0.6 and 2.0 Ohms
If your readings are not within these parameters you may have bad injector, glow plug or loose connector under the valve cover.
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