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With a Diesel there are additional parts that you have which affect the Cold start. There is a timer between the glowplugs and the Power relay on the start circuit. The timer cycles the glowplugs off/on for a variable time period. The more cold, the longer the cycle period. Glowplugs go bad. You remove them like sparkplugs. Testing them is a matter of comparison. When power is applied they can melt, so test with care. Hook battery jump cables to each glowplug taking care to attach one lead to the base (avoiding the threads) and then briefly touch the top of the glowplug. The quicker the plug glows, the better it is. The darker, the worse it is. But the timer must provide the juice to the glowplug for it to work. A bad timer will not properly heat the glowplugs. The timer must get its' power from the Power relay. So you can have acceptable glowplugs, and a bad timer. Ultimately once the engine cylinders have run hot enough, a Diesel fires by compression and not by spark as a gas motor does. That is why once you have a hot diesel, it will start freely. It is why I explained the needs of a Cold Diesel engine and I hope this helps you.
!st thing is get the revised head gasket (used on 1993 up) for this engine from VW or Felpro, always use new head bolts or a repeat failure will occur. Using the revised head gasket here is the procedure to torque the head down, it is done in stages. PLease go to this site and read the whole procedure.
Hello, The diesel engine relies on Glowplugs for the first start in the Morning or a cold start at anytime.
The Glowplugs themselves can be bad, but there is a Timer which determines how long the Glowplugs will stay on. Before the Timer is a Glowplug Relay which gives the Timer its power to operate. The Ignition switch provides power to the Glowplug Relay.
You disconnect a Glowplug wire, put on a test instrument (either a testlight or Voltmeter) and look to see what happens when you initiate a start. If the testlight lights and cycles a few times like a pulse, then the power supply is good. If not inspect the Timer and Glowplug Relay for continuity
If all the pulses seem to reach the Glowplugs, then most likely the Glowplugs are worn out. Test by removing then and connecting battery jumpers. Briefly touch the top terminal of the Glowplug with the Hot cable after grounding the negative cable on the base of the Glowplug, avoiding the threads.
You can melt a Glowplug. But if you find the Glowplug staying dark, then it is bad. Do this for all the Glowplugs and replace the bad ones. Remember the Glowplug only has the amount of time the Timer gives it to work. So if a few pulses do not make it Glow, then replace it. This should fix you up.
It sounds like your Glowplug timer or the Glowplugs are bad. The reason that turning the Key 4 or 5 times helps, is that everytime you put the Key to RUN or START you are energizing the Glowplug timer and reheating the Glowplugs.
You can check the Glowplugs by removing them and remove at least 1 bank at a time. Get some jumper cables and put the NEG post on the plug without smashing the threads. Take the POS cable and touch the Glowplug till it starts to Glow. You can mess up and melt the Glowplug so watch it. BUT, as you test you will find the bad Glowplugs will not light or will take longer to light up.
This is the reason I said to take out 4 plugs at a time, minimum, because you need to compare bad and good, visually.
The timer is not as easy to test. It is a variable timer and the warmer an engine is, the less time it will work. Obviously if the Glowplugs are not Hot, the timer is cutting off too early. But you check your Glowplugs first. The Glowplugs help to give a Feedback loop which tells the timer to stay on.
The rough idle is because the glowplug is not hot or the compression is bad in the cylinder.
I just went through this problem. Believe it or not their is a air conditioner for the turbo. Located on the back side of the turbo a real mother to change. Almost $400 for the part alone and another $200 for the install at the VW dealership. I recommed that you go to them and get it done instead of a back yard mechnanic or yourself. Al
What you have described is a classic turbo air leak. Check the clamps & air lines from the turbo to the intake. If you do not find an air leak (you should be able to hear the air escaping) it will be a turbo problem. Unlike gasoline engines too much fuel in proportion to the air will cause the vehicle to run hot and also to smoke.