Go with optima yellow top batteries and replace the hot cable with a deka brand cable. Remove and clean both ends of all the ground cables. Clean bright connections, don't half ass it. This ensures the starter will receive full amps from the batteries and therefore turn the engine at optimum rpm for a good ignition.
Check all eight glow plugs with a continuity light. Clip it on the hot battery terminal and then touch the center of each plug with the probe end. If the plug is functional the continuity light will illuminate, if it's burned out the light remains extinguished. Burned out plug is an open circuit. Carefully remove the unserviceable plugs with a 3/8 " six point, deep well socket. Break the torque then spray the threads with penetrating oil and slowly work the plug loose. If it starts to bind do not force, just work it in and out while adding more penetrating oil. The oil will help ease out a swollen element, just be patient and you won't break off the element. Replace them with beru glow plugs only please. You'll regret it soon if you use any other brand. If all eight plugs are functional and the relay is working your wait to start light will remain illuminated for a longer period when the engine is cold and shorter when it is warm.
If all is well the engine will start within three turns. Excessive cranking to achieve engine start at this point is usually caused by air intrusion of the fuel system. There are multiple points of entry for air intrusion, but most often it's because of leaky return lines. As the return lines cool down after engine shutoff they will create negative pressure thus sucking in air through the same points of leakage. Repair the leaks, by doing so you will also eliminate the air intrusion into the fuel system. If there aren't any leaks then check the fuel pressure created by the fuel lift pump. This is accomplished through the schrader valve that is located on the fuel filter head. The pressure reading will pulsate, but should produce a minimum of six psi. Any less requires removal and replacement of the fuel lift pump.
The injector pump from the factory is painted grey along with the rest of the engine. That's how you will know if it's original. If it is, be prepared to remove and replace it soon. They are rated to have a service life of 100k miles. Mine lasted 300k miles before it started to go. I replaced it at 330k. When you do, unbolt it from the timing gear through the forward access panel located on the front of the timing gear cover. Clock the installed replacement pump by lining up the stamped line on the pump flange with the stamped line on the mounting surface then tighten the flange bolts. This won't be perfect timing but it's a good starting point, good enough for the engine to idle. If you're happy with how it idles and how it operates under load then leave it there. If not, then advancing the timing is by rotating the pump toward the passenger side and retarding is by rotating toward the driver side, as you face the front of the engine. If you want precision be prepared to search for a unicorn. Took me two years to find the correct equipment to accomplish a precise timing adjustment. Never adjust the timing with the engine running. Doing so will cause damage. Readjust the throttle position sensor, or whatever you'd like to call it, with a volt/ohm meter or else the automatic transmission will not shift properly. Leave the lines loose at the injectors to bleed out the air, tighten them individually as you see fuel seeping out of the fittings. It's easier with a bump switch connected to your starter solenoid, but keep your power disconnected from the glow plug relay as an added precaution, until all lines are purged of air.
If the operating engine begins to sputter and cut off at 1/4 of a tank of fuel it's because the pickup tube, or shower head, whatever you wish to call it, has broken off and fallen into the tank. Remove the tank, remove the sender assembly then add a section of 3/8 fuel line, with a bird notch at the end that will come in contact with the bottom of the tank, to the metal tube of the sender. This replaces the pickup tube and allows access to the entire capacity of your fuel tank.
If the bottom of your fuel tank feels like it has a coat of slime, it has microbiological contamination. This will cause constant replacement of the fuel filter until it is eliminated. Pour a gallon of isopropyl alcohol into the fuel tank and let sit over night, dump it out the next day and blow it out with compressed air before reinstalling. Consider adding fuel treatment specifically for microbial contamination, to eliminate possible contamination between the fuel tank and the fuel filter element.
Excessive engine oil consumption or excessive amounts of oil within the air intake ducting is indicative of a faulty crankcase depression relief valve. Remove and replace with a new or serviceable valve.
Make sure to check the level of sca additive within the coolant in order to prevent cylinder cavitation. Or just add two bottles of sca at the radiator cap for good measure. It's available from napa. Don't bother going anywhere else unless you enjoy a lengthy exercise in futility.
There's a **** ton more to look out for, but nothing that's rocket surgery or brain science. Or whatever description of overly difficult tasks you prefer. I'm willing to add more to this thread because I'm in Kabul for three more months otherwise I'd be replacing my power steering gearbox and pump along with the associated pressure and return lines. Never a dull moment with a 360k 92 turbo idi. Enjoy your idi and remember, never buy commy replacement parts. If you don't have the scratch just wait until you do. Your down time will stay the same either way, but you won't be fixing the same **** twice. Or more, if you're just sadistic. Later fellas.