Bleeding air out and bubbling injector seal? - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• Bleeding air out and bubbling injector seal? by hibernatingbear on 04 Mar, 2015 16:44
• Hey guys,
  
  My car starts and runs every day. But on cold starts I get a rough idle and smoke then once it's warmed up it takes a little start to crank over.
  
  I have a new Giles pump that I had a local shop install. But later I changed my glow plugs and without realizing I cracked the clear line going from the filter to pump. I did replaced that but ibky after I tried to start the car for a couple minutes.
  
  Today I went to bleed the air out of the system at the injector point. This is how I did it:
  
  Started car, at warm running I cracked open the first (left) fuel line. Fuel and air bubbles came out (little foam bubbles). That didn't stop but after about 30 seconds I tightened it up and moved one to the next one. Same thing through all 4. But the bubbles never stopped so I did it again and revved the motor a little. It was spraying/spitting fuel everywhere. I used a towel to catch most.
  
  I wasn't sure if those foam bubbles were normal or not, I'm guessing not. But they never stopped.
  
  So basically I'm not sure what I should be seeing for me to know the air is gone.
  
  Also when I did that, a little fuel pooled up on the injectors and I noticed the 3rd cyl bubbling like air is escaping. Obviously not good.
  
  At this point should I even worry about bleeding the system more or deal with it after I change the injectors? I will replace them soon, just don't have the funds right now.
  
  Sorry for the long post, I just wanted to make sure you guys know exactly what is going on.
  
  Any information would be nice and very much appreciated.
  
  Cheers guys!
• #1 by ORCoaster on 04 Mar, 2015 21:57
• Normally getting air out of the pump just takes some revving of the engine.  Sounds like that is what happened to you but the bleed at the nuts could have sped that process along.
  
  Where did the fuel pool up on the #3 injector?  It might be that the injector is not well seated in the head or not tight between the two parts that make it whole. 
  
  Bleed the system now and then again when you find the coin to replace the injectors. 
  
  A bit of clear hose from the out bolt to the fuel tank is a good way to determine if all the air is out of the pump.  It may be a seal is out or on its way out and you are getting some air in that way.  The break in the line as you described would for sure suck in air to kill the pump drawing it in.   
• #2 by air-cooled or diesel on 05 Mar, 2015 04:57
• there should be only a very small amount of air in the inside of fuel system, from tank to injectors needs to be sealed. if you have clear line on from filter to pump inlet you should have 3-5 small bubbles, any more and something there is sucking air in, maybe the line you replaced? its hard to figure if air is in system by cracking injectors, if it is air in pump thats bad, but the pressure and ambient air can make bubbles. i dont figure air is a big prob in out let side, there is some air in that side, it returns to tank. it takes a few minutes of running to get all the air out,
  if you have the tools you can tighten injector, but it prob needs a heat shield too, make sure you loosen/tighten injector Correctly, about 51-52ftlbs, using Correct pattern! dont overtighten inj lines either.
• #3 by hibernatingbear on 05 Mar, 2015 13:40
• It looks like it's bubbling right at the injector seal. Right at the edge of the block.
  
  I've been planning to get clear lines but just wasn't really a priority.
  
  I'm a little worried about tightening the injector but I will make sure it's torqued correctly.
  
  Thanks for the info guys.
  
• #4 by air-cooled or diesel on 05 Mar, 2015 15:54
• mount is more of a seat than a seal. you need a new heat shield, 1/2"torque wrench, 27mm inj socket(deep), and an extension, 51-52ftlbs.
  *when you loosen and tighten you do at the opposite of each other, you go toward head, so when you tighten your using your left hand to go clockwise/right up towards head. (pic in shop manual).
• #5 by ORCoaster on 05 Mar, 2015 20:42
• When I read "correct pattern" I was wondering if he meant correct direction.  As you have stated it is correct to push toward the head for both the take off and reinstall of the injector.  Never pull out towards the radiator or you risk snapping the outside of the head off or cracking in some place.  I had a head that was puzzling me for a while with a faint line behind the injector pump.  I finally found it the hard way.  Removed the injector and the piece totally let go.  A 400 dollar mistake. 
  
  So careful up  there, mr mechanic. 
• #6 by hibernatingbear on 05 Mar, 2015 21:00
• Thanks guys! I'll try changing the shield first.
  
  I'll have my Bentley around to triple check myself in the moment.
  
• #7 by air-cooled or diesel on 06 Mar, 2015 06:34
• Quote from: ORCoaster on 05 Mar, 2015 20:42

  A 400 dollar mistake. 
  

  yea only the Head ran you $400, the rest of the parts add up, cam $150-200,lifters, valves$30 a piece, springs $25 a piece, and some more, i found a good head complete, he wanted $1100 for it.
  and by pattern i inferred the push toward head not pull 'method', i figured youd all get that as a pattern type of thingie
• #8 by TylerDurden on 06 Mar, 2015 07:38
• Bubbles or foam in the outlet/return line are critical evidence of an air leak, particularly if the inlet line is solid fuel.
  
  Air can be drawn into the pump through the main seal and/or the inlet fitting. Air can also intrude to the return line via the injector returns.
  
  When air can get into the system, the fuel can drain back to the tank in both directions, making a good start and running very difficult.
  
  When air is in the pump, it can get into the injector lines and cause the injectors to open late or not at all. Air in the pump also keeps the dynamic advance from functioning properly, causing retarded timing.
• #9 by air-cooled or diesel on 06 Mar, 2015 07:58
• some air is already in the return/over-flow lines. the main thing I was stressing is almost No air bubbles in inlet side(from filter to inlet pump), like 3-5 small bubbles max, & clear lines there @inlet. i didnt do that, i ended up accidentally snapping factory clear line(which was cloudy by then), so i got a couple lengths of ok efi line and ran it all around, i thought at one time, not too long ago i had some small leakage from main seal, on further inspection with a light&mirror i found no moisture there, so that is clear. i do have a small problem somewhere in inlet system, when fuel gets real cold and i dont use enough anti-gel i find fuel freezes or something and get some of my lines draining, and pump wont prime its self by cranking engine, so i have to prime the inlet side manually and start and clear out the air that gets in. it may be the water seperator, although it doesnt seem fuel back there is draining off/back, the inlet seems dry, i cannt trace prob yet, and dont have a major issue with it.
• #10 by TylerDurden on 06 Mar, 2015 08:13
• The main seal is under vacuum, not pressure. Fuel does not often leak out there.
• #11 by libbydiesel on 14 Mar, 2015 18:44
• If you open the injector unions, you will usually see bubbles there.
  
  Also, if fuel leaks down around the injector and then you run the engine you will ALWAYS see it bubble out as the fuel in the threads boils and evaporates out.  It can certainly look like an air leak, but it isn't.  Everything sounds normal to me. 
• #12 by mtrans on 15 Mar, 2015 14:11
• Quote from: air-cooled or diesel on 06 Mar, 2015 07:58

  i find fuel freezes or something and get some of my lines draining, and pump wont prime its self by cranking engine
  

  
  Does disel from tank must have one way valve or something like that,just because of that?
  I remove stock fuel line with 1/2" line long time ago so I didn`t know.
  I dont like oneway because in winter I find  is "glue" and my stock lift fuel pump cant start.but perhaps is only that one model.