[Vwdiesel] 98 TDI no glow

[jonathan hoehl]

I need some help.

 

Same tdi that wouldn't start a few months ago.  Timing cog changed and timing perfectly set.  Engine runs great!  But, no glow cycle.  When you turn the key, the glow plug light comes-on for a second then turns right off.  It acts like the engine is already hot, when it's not.  The temperature gauge reads as it should too.  If I disconnect the 4-pin coolant temp sensor that's right next to the head, the temperature gauge doesn't work, the computer seems to think the engine is always cold (adjusts timing accordingly), and the glow plugs stay-on for quite a while (20 seconds maybe?!, seems kinda long).  This is an AHU engine and I got the car with a black 4-pin coolant temp sensor with a yellow paint dot on it.  I bought a new black 4-pin coolant temp sensor from the dealer with a blue plastic ring around it.  They said this blue one is the correct replacement.  Both temp sensors make the car act in the same fashion.  Basically the car runs fine and everything works correctly when the engine is WARM and with either (yellow or blue) coolant temp sensor plugged-in.  Seemingly because I don't need the glow plugs to start the car when the engine is already warm.  The problem is a cold start, the glow plugs won't cycle and the engine won't start without them - unless I unplug the temp sensor and the glow plugs cycle 'as they should'.  

 

Does anyone have a thought about what could be wrong?  And, is anyone using a different temp sensor for this engine?  I can't remember if this is related, but the brake lights are ok.  

 

Jon

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