m-TDI loads up when cold?????

[MichaelBuck]

I'm running: AHU, 12mm 4BT (timing set at .9mm as per pump builder), pp520s, 23+ boost in a Syncro Vanagon.  Have had this quirk since the conversion:  I start the van from cold and drive away.  As I climb in RPM and push it slightly past 3000 it is as if a switch goes off.  The engine begins to shake and buck and smoke.  I have to back off the pedal and baby it for 30 seconds or so until it cleans out and assumes normal operation.  As soon as the temp needles moves a little I have the full RPM range available without the fear of reprisal.  Now, I've assumed it was loading up because of the bucking and smoking but that is just that - an assumption - because I'm not as knowledgeable as I'd like to be.  Other wise the van drives great!  Can anyone shed some light on this for me.  TIA

Michael

EDITS and extra info for this post below.

[dillenger1]

are you using the 4bt governor spring?

[MichaelBuck]

are you using the 4bt governor spring?

Don't believe so.  Builder says it should run up to 4500 which is more than the 4bt allows.

[jtanguay]

just a theory, but it could be the cold fuel not getting the right injection spray/timing.

mine reacts similar.  it'll rev when cold, but seems like a totally different engine.

[burn_your_money]

As I climb in RPM and push it slightly past 3000 it is as if a switch goes off.  The engine begins to shake and buck and smoke.  I have to back off the pedal and baby it for 30 seconds or so until it cleans out and assumes normal operation.  

Kind of sounds like an injector sticking open to me. But that'd be rather strange if it did this everytime and always under the same conditions.

Try running it out of a jerry can using a different filter. It may be starving itself.

[MichaelBuck]

I'm not dealing with any other issues at this time so I'm going to dredge this up again as I haven't a clue what is causing it.  I'll add some details to help with diagnosis.  The smoke has a blue cast to to it (no black at all!).  It will also happen at 4k RPM after the warm up has begun but is not completed.  As I said in the initial post it will go away at operating temperature and I can then run it up to the redline without the symptom manifesting. 

Having mentioned the bluish cast to the smoke  and the suddenness with which it comes on, I began to wonder if maybe the CCV puck is tired.   Thus as the the turbo starts sucking real hard it pulls the puck open and sucks any oil residue in to the intake stream.  It doesn't seem likely at the cold temps there would be enough vapor to cause this but......?  To take my mental wanderings a bit further - the engine warms the puck and the seal becomes more pliable and is not as likely to stick open and suck oil.  My CCV hose from the puck enters the intake 5-6" from the turbo in, if that matters. 

I'm reaching for straws in the dark and laden with ignorance.  I could be very far off and so I'm hoping for an expert intervention.  The pump needs to go back for minor upgrades but the builder did not experience this when he tested it on his own rig. 

TIA
MIchael

[Rabbit on Roids]

that problem you are refering to, could be solved with a clean air filter. you shouldnt have much, if any vacuum ahead of the turbo. i doubt the puck is your problem. besides, there isnt anything in them, least not the ones ive broke open. its just baffles and stuff to keep the oil in the engine.

[MichaelBuck]

RoR,
Thanks for talking with me!  I'm alright that it isn't the puck.  However, I'm running a Donaldson canister filter big enough to use on small equipment with 2.5" hose.  I would think that filter would flow well enough to keep up.  Oh and it has a new element right now.  If it were filter restriction, why would it fade from possibility as the engine warms?  Also others are using the same filter without reporting this quirk.

I have an Informer restriction monitor to install that would tell me how much it's pulling at the filter.  I haven't installed it yet as I have to disassemble much to get it to the tap on the housing. 

Michael

[Rabbit on Roids]

hey, a local, i completely missed that!

anyway, like someone else was saying, did you change your fuel filter yet? cause diesel is thicker when its cold than when its warm. so as its cold, it could "load up" as you describe. altho there is no way for a diesel to load up, its just not possible with the way they run. a load up on a diesel would more than likely cause a hydro-lock condition. have you had your injectors tested? have you talked to libbybapa yet? hes working on a MTDI van also, with a smokey start up. maybe you both have the same problem?

[MichaelBuck]

Yeah I noticed your PNW label.  Man I love living in Oregon!!!   IF we could just make some money in the rural areas it would be the total shizz.

Yepper on the fuel filter.  I'm using a 150 micro prefilter and stanedyne FM100 head with a 5 micron final.  I don't have a heater or a lift pump.  Edumacate me - How will the fuel availability bring this on.  And if this is what is going on, what would you call it?

I did have the injectors cleaned and popped at Northwest Factors about a year ago.  Let me throw this at you:  Say I bought some Bosio PP520s and they weren't actually Bosios but rather a knockoff, could we postulate that as a source of difficulty leading to this symptom?  When fully warm it runs REALLY good.  When loaded (family of five with gear and 500# trailer), I can pull a moderate pass at 60mph.

I know Andrew is here and if he doesn't find our conversation I'll pull him in with a PM.

Michael

[Vincent Waldon]

If I understand your description correctly  we see this same behavior on IDI engines sometimes as well... on my old Rabbit truck it expressed itself as running ruff, lots of white smoke, power issues, until you gave it 30 seconds to smarten up.  When it happened I found I could "hurry up" how quickly it smartened up by popping the clutch and stepping on the throttle... engine would cough, spit, complain, and then even out and rev up.  Foot off the accelerator and all was right with the world until the next time the engine was stone cold.

My theory at the time was one or more injectors that spray poorly at cold temperatures, yet fine at room temperature on the workbench.  30 seconds seems about the right amount of time for something to warm up and make the problem go away... and the only fuel-related something I could see warming up in 30 seconds is the injectors themselves.

My current IDI doesn't do this... but the next time I find one I'm gonna pop-test the injectors after they've been in the freezer overnight... and then again at room temperature.

[MichaelBuck]

Vince,
Did you cure it or live with it?  Mine definitely takes a bit longer than 30 sec.  Under your theory would you say it is improper pop, poor quality noozle, or

Thanks
Michael

[Vincent Waldon]

Lived with it for the winter (didn't have a pop tester at that point) and the shock towers rusted out before the next winter.

It's just a theory... nozzle performs poorly when cold but fine at room temperature on a test bench... in my case the nozzles were genuine German Bosch so I wasn't worried about quality issues... was thinking wear.

My overall point is that if a vehicle performs poorly when cold and then gets better quick... likely because "something" has warmed up... testing things when cold might help narrow down the problem.

Same goes for compression... I've seen some huge differences in an engine's compression when stone cold vs warm....yet the factory test (and specs) are for a nice warm engine... makes it difficult to find a cold start issue if you're testing warm compression?!

So, in your case, if you can convince yourself that your issue must be temperature related I'd be inclined to have your injectors tested when cold.  But again... it's just a theory!! 

[westyventures]

What's the cold oil pressure? I've seen the oil pump relief valve stick and cause too much oil pressure to pump the cam followers up to a point where the valves start to hang open, = loss of some compression and gobs of smoke, will eventually sort itself out and disappear when warm.

[MichaelBuck]

Karl,
Thanks for joining in!!  I've not added a oil pressure gauge so I can't say how it is.  I've been waiting til I can afford to add a pair of dual sweep gauges to cover the vitals.  I cleaned the pump really good when I installed it, however, it was the pump that came with the pan and etc. from England. 

Would this allow oil into the cylinders?  re. 'bluish' smoke

When you saw this did it get resolved?  If so, how?

Michael