AAZ bad cold start - what to check - fixed - Troubleshooting - VWDiesel.net The IDI, TDI, and mTDI source.

• AAZ bad cold start - what to check - fixed by TITan on 11 Feb, 2019 11:03
• Fixed
  
  Hi boys/girls.
  
  In the last month my AAZ has developed a rough start (more like no start) condition when it's cold. It started when it was really cold (-5°c/23°f or lower) but would start when it was about 7°c/45°f outside. Now it doesn't want to start even when its 10°c/50°f. I haven't put 300km/190miles on it since it started acting up, but has been getting worse and worse. Cycling the glow plugs a couple of times before cranking doesn't help. When it does start it slowly catches one cylinder, than another... with lot's of first white than black smoke from un-burned diesel.
  I have a auxiliary water heater (webasto thermo top C) installed and when I preheat the coolant by at least a bit (let's say to 30°c/86°f) it starts up like nothing is wrong. When I'm driving there's maybe a bit more black smoke than usually (or I'm just more focused on it) but the power is all there.
  
  The car cranks well (2.5 TDI Audi A6 starter on two 70Ah batteries).
  Tested the glow plugs in the engine and they all take about 10A. Haven't taken them out and verified that they actually glow.
  Don't have the cold start lever active, but tried to bump the timing up (and down) a bit with no luck).
  Running 5W-40 full synthetic oil.
  Replaced the wobbling crank pulley last year.
  AAZ running about 1bar/14 pounds boost on a Garrett T2. The pump has the boost pin aggressively grind down and I did the governor mod.
  No bubbling/pressure build up in the coolant system and there is no pudding on the oil cap/oil looks as good as a diesels oil can.
  I am getting some blow by thru the breather.
  No bubbles in fuel line to the pump. The diesel looks normal.
  
  I probably won't have time to touch it till the weekend so I'd like to make a list of what I could check since time will be a bit tight. I currently have:
  -Check cam timing
  -Check pump timing with a dial again
  -Remove glow plugs and see if they are indeed glowing.
  -I'd love to do a compression and leak down test but I don't have the equipment to do it on a diesel. I'm guessing that's something I have to look into...
  
  Any other ideas? Really hope it's not the rings (but that would be my first guess for now). The engine will get replaced with a TDI but I really hopped to get my Scirocco on the street before I tackled  that so it would be great to keep this engine going for a year or so longer...
  
  Pic of the car for attention 
  
  
• #1 by libbydiesel on 11 Feb, 2019 12:04
• The 'Free Candy' is really bad taste.  Pedophilia and kidnapping is no joke.  Don't be surprised if you come out to your van some day to find a few windows smashed, etc...  Just saying. 
  
  It sounds like the glow plugs are not firing in those intermediate temps.  You might try disconnecting the wire to the temp sensor that goes to the glow plug relay.  The glow plugs will then always glow full length.  See if it starts easily then.   
• #2 by ORCoaster on 11 Feb, 2019 22:52
• I thought someone just was super evil and tagged his ride.
  
  Without the use of that cold start lever you are missing out on a few degrees of advance.  Bumping the pump to make it like that all the time is not what you want.  You want to be able to manually invoke that extra few degrees without relying on the internals of the pump pressure and such to get it to you.
  
  I know getting that lever good and functional is like a major PITA but, if you are that cold then you NEED that lever working.  Some pumps even had the high idle bump mechanism on it too so that would be an ever better thing as you could have the engine purring a bit higher RPM's while cleaning the windshield and it would warm up faster.  Likely about the time you crawled back inside. 
  
  
  I would for sure be testing the GP's and that system.  With the dual batteries there is no reason why that thing shouldn't be firing right up. 
• #3 by libbydiesel on 11 Feb, 2019 23:53
• I missed the comment that the cold start lever is not working.  Well, um, fix that first.
• #4 by TITan on 13 Feb, 2019 13:03
• Thanks for the input everybody. The problem is fixed.
  
  Unfortunately retrofiring a cold start lever would take about as much time as the TDI swap  But it's been working for me for over 6 years like that.
  
  I un-pluged the temp sensor for the glow plug relay, heated the plugs the whole 30s and the starting wasn't any better. But then I rechecked the the current and it was down to about 25A. So ok it seemed to be two plugs down. Used a IR thermometer and only one plug was actually heating up. I have no idea how, but it's not the first time a plug still took current but didn't glow. Two hours of cussing later and I installed four used but good plugs with a updated harness and it started up right away.
  
  Me and my dad have both been using Beru plugs as of late and have both have them go out way too quickly (like 15k km for this ones). What plugs do you guys recommend (The plugs I robbed from a spare 1.6TD head are NGK and were in use way longer than the dead Berus were).
  
  
  
  Thanks again!
• #5 by ORCoaster on 13 Feb, 2019 14:06
• Yepper, I bet the majority of poor starting in the cold problems are caused by the fact that you don't have 4 plugs a glowing.  Glad you got it fired up.  Cussing at a car doesn't do any good by the way.  It generally does more harm to you than good.  It might cost you a knuckle or two as well. 
  
  That has been my experience over the last 40 or so years.
  
  
• #6 by TITan on 13 Feb, 2019 15:57
• Quote from: ORCoaster on 13 Feb, 2019 14:06

  Cussing at a car doesn't do any good by the way.  It generally does more harm to you than good.  It might cost you a knuckle or two as well.
  

  
  The cussing was AFTER the knuckle busting 
• #7 by libbydiesel on 13 Feb, 2019 18:41
• Replacing the glow plugs is easy unless you try to do it without spending the 1 minute it takes to remove the metal injection lines.  I'm not sure what might be cuss-worthy.   
• #8 by TITan on 13 Feb, 2019 18:57
• Quote from: libbydiesel on 13 Feb, 2019 18:41

  Replacing the glow plugs is easy unless you try to do it without spending the 1 minute it takes to remove the metal injection lines.
  

  
  You have no idea how big of a idiot I feel right now 
  Ahhhhh... You live and learn. I guess I know for the next time 
• #9 by ORCoaster on 13 Feb, 2019 20:27
• Experience the teacher of many, the fool of none.