You can check resistance on your glow plugs and injectors at the rectangular valve cover harness. Marty did a write up on the glow plugs, and DND58 filled me in on the readings for the injectors...here you go:
5a) Voltmeter method - Remove the large rectangular plug leading to the valve covers on either side of the engine. This plug powers your glow plugs and injectors. The 2 outside pins are your glow plugs, the 4 inner ones are for the injectors. () () () () () () () () ()
Blue is the Glow Plugs Red is the injectors, Black is the common for the injectors. Be very careful not to insert your test lead into one of the injector pins. The IDM feeds the injectors 110V and could cause a lot of sparks if it happens to try and actuate the injectors while you're testing, and could worse destroy the IDM, so steer clear of those and make sure you test only the 2 outer pins on each side of the plug.
Connect the ground lead of your voltmeter to a good ground, and insert the positive + test lead into the first glow plug pin.
A good glow plug will read btwn 0.8 - 1.2 ohms a weak glow plug will have much less resistance, and a completely dead one will have unlimited resistance through it because the electrode is internally burned out. Make note of the plugs that are out of range based on the cylinder number, and replace them. The cylinders are numbered 1-3-5-7 on the pass side, front to back, and 2-4-6-8 on the driver's side, front to back.
Test on the pins going into the valve cover to read resistance from the glow plugs and injectors.
G G I I C I I G G
Test between "I" and "C" to test the injectors, should be less than 5.0 Ohms.
Test between "G" and battery ground to test glow plugs. Should be between 0.6 and 2.0 Ohms
you can use something like this: