Narrowing it down...cold start issue - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• Narrowing it down...cold start issue by Jettage1 on 22 May, 2009 04:40
• Okay, here goes:
  
  Car:  92 ECO, with Giles TD pump.  Giles-rebuilt TD injectors, new Duraterm glow plugs, thoroughly cleaned buss bar when I put in plugs.  While doing some other work, my mechanic later confirmed that plugs are indeed glowing.  Compression is 350-400 on all cyls, IIRC.  Timing set 95-96 per Giles (due to performance pump).
  
  Symptom:  when stone cold, and outside temps are say <47 F, starting is very rough.  Pull cold start lever out fully, cranks fine, catches quickly, but misses badly - feels like one or two cyls are just along for the ride.  Clears up after the first 20 seconds or so.  It has not always behaved like this, so I know something's not right.
  
  I'm running out of ideas.  Maybe the plugs are glowing but not getting full voltage to get to max temp??  What else am I missing here?
  
• #1 by Rabbit TD on 22 May, 2009 17:26
• Are you  saying it ran good with the Giles pump and injectors before your mechanic touched it with the timing at his {Giles} recomended settings?  If it did and was set at that position before it almost surely isn't set to where it was now.  I'd bump it up a little. 
• #2 by Smokey Eddy on 22 May, 2009 17:55
• I have the same thing going on right now after changing my crank sprocket. IE. i had to redo the timing. It's too retarded and i have the same problem. I'd loosen the 4 bolts holding the pump and push it towards the head slightly until the issues goes away. I'm sure, as stated above, that it's slightly retarded timing.
• #3 by Jettage1 on 22 May, 2009 18:12
• I have tried the timing as high as 1.05 since installing the new pump and injectors, but the problem has still been there.  A bit better with more advance, but that didn't cure it.  Giles specifies the relatively lower setting due, I believe, to a more aggressive advance curve in his pumps.
  
  I don't recall having the problem prior to doing the belt, tensioner, pump, injector, glowplug, waterpump, all-inclusive changefest.
• #4 by jtanguay on 23 May, 2009 08:04
• my money is on a fuel related problem.  my fuel 'pre-heater' was leaking air so i changed the filter for one without it.  car starts much better, and no air bubbles in the fuel line.  it took about 6-8 hours for the air to seep in, and the hard starting is the pump bleeding out the air.  get the problem fixed asap as cavitation in the pump is very bad.
• #5 by Rabbit on Roids on 23 May, 2009 11:05
• timing, timing, timing...
  ive never messed with such a PICKY engine.
  like they say with the pencil marks, it actually works.
  move your pump a half of a pencil line.
  my ride used to start and idle like crap.
  then i started bumping my timing, and i got it pretty god damn close.
  fires up good cold now. but that also had some help from cleaning every connection in the glow plug system.
  its amazing how well they start when your GP's get nice and hot.
• #6 by theman53 on 23 May, 2009 11:23
• Yeah I am with the other guys here. Either timing or slow air leak or a little of both. Mine would do almost the same did it for about a year and then it started to not catch right away, and got slower, and idled rougher. I checked the timing over and advanced it from about .037 to .040. It got a little better, but when I replaced the fuel filter and some send and return lines it pretty much cleared it up. If it isn't one of the two problems or both I'd be surprised.
• #7 by Rabbit on Roids on 23 May, 2009 11:31
• yea, fuel filters have caused me problems that you wouldnt think were fuel related. when i replaced my fuel lines, filter, and added a lift pump, my car really came alive. the IP has to have alot of fuel flowing to it at high RPM's its almost time to do a new filter on mine again, its starting to surge at higher rpms. and it doesnt blow near the black cloud it used to.
• #8 by Jettage1 on 23 May, 2009 12:07
• Hmmm.  Gonna take a closer look for the slow air bleed previously mentioned.  I think (in my case) that has potential.  I need to first replace the plastic lines, though - they're so opaque I can't see through them anymore to tell if there's bubbles.  I have already changed the fuel filter preheater plastic junction thingy a few months ago.  Highway robbery (~$40), but mine was leaking...
  
  I do get some odd surging (not a loose IP, either) at mid to light acceleration.  Not enough to "buck" but again, it's a newer thing that wasn't there previously.  I have my doubts that it's related to cold start, but you never know, I guess.
  
  Thanks for all the replies...  Keep 'em coming - looks like we're helping several folks here!
• #9 by burn_your_money on 23 May, 2009 12:35
• Was your compression checked with the engine hot or cold?
• #10 by Rabbit on Roids on 23 May, 2009 12:41
• fuel pre heaters must be a MK2 only thing? all the rabbits ive worked on... no fuel heater.
  and the surging i was talking about, it only comes on when im absolutely firewalled on the pedal. (WOT)
  it doesnt come on at first (because the fuel pump is full of fuel im assuming)
  then it comes on slightly (because the pump is sucking all the fuel out of its self and cant replace it fast enough?)
  then as you keep the throttle wooded, it starts loosing boost, almost like a clogged fuel filter. its really strange, how it acts.
  and its not consistent either. some days its worse than others.
  
  not like it really matters at this point, im not driving the car, and i have all the plumbing ripped off of it, i just managed to get my hands on a free T3. and with the amount of boredom in my life lately, i got this wild idea that im gonna put it on my car also. hell with it, cant really hurt.. A VNT17 and a chrystler T3, if it doesnt work, im not really out anything besides my time and welding wire. if it works, i know i will have enough boost to break ***. i have already blown a head off with just my VNT. and it cracked 7 bolt holes when it blew off... the messed up part, i ended up driving the car home. not that night, but i drove it home. took 4 gallons of water to go 2.2 miles.  
• #11 by Jettage1 on 23 May, 2009 13:37
• Tyler,
  
  I don't know if it was hot or cold - I had my VW mechanic do it as I don't have a compression tester.  I'll have to ask.
  
  Just looked up the readings:
  1 - 425
  2 - 425
  3 - 400
  4 - 375
• #12 by Jettage1 on 23 May, 2009 18:18
• Wait...  regarding air in the fuel lines:  If the outdoor air temp is - say - above 50, the car starts fine, even if it's been sitting overnight.  Air is air, regardless of temp - unless I'm missing something.
  
  So if my car misses only under 50 deg. F, I'm thinking it ain't air in the fuel lines.
  
  Comments?  Critiques?
• #13 by theman53 on 23 May, 2009 19:15
• Maybe it is warm enough that it doesn't matter? Or the leak isn't bad enough to cause it to stumble, yet? Just some ideas. I would still check both fuel and timing issues.