Rough idling + smoke on cold start 1.6 eco (1V) TD engine

[kvcuijck]

Hi there!

I have a (for me) strange problem with my 1.6 (1V) engine build in a '90 Golf/Rabbit type II.

When I cold start the engine it runs within seconds but idles very rough coupled with a lot of smoke. (I have to use the cold start choke.) This "behaviour" continues during the first 10km's or so when the engine warms up.
It feels like a "misfire" or air bubbles in the fuel lines (checked that). Once warm (25km) the rough running is almost gone.

It all started after we timed the diesel pump with the right tools (and experience). It was way ahead with a value of 1.4. We set it at 1.0. Since then the problems got worse.

Some facts:
- With warm temps outside cold start problem is much less
- Injectors have been replaced
- Always starts first time after 2 or 3 cranks (so no glowplug problem)
- Internal dieselpump pressure within specs
- Fuel economy has dropped since new timing dieselpump
- Idle revs are set and checked

Does anyone see the connection/logic between timing the pump and the problem above?

Hope for some good advice! Thank you.

Regards,

Koen

[Baxter]

Maybe the pump in internally worn, you are getting the correct reading with the micrometer but it really runs retarded due to wear.
can you set it dynamically?
I.E use a Diesel pulse adapter and a conventional timing light?

[kvcuijck]

Mmm, I've heard that before. But if the pump is internally worn (and it can be after 300.000km's ofcourse) why would it run okay-ish with engine warm and bad with engine cold?

I've never set a dieselpump without the dial. How does this procedure work if I can find a pulse adapter and conventional timing light? Is there any scale to read the timing from?

How bad is it for the engine to run this retarded?

Thanks for your help!

Koen

[Baxter]

If pump head is worn, you will get the right amount of movement on it, but as fuel leaks past the piston it will take longer for it to build enough pressure to pop the injectors open.
you will end up with retarded timing.
I think whoever set the pump before you has advanced it to take into consideration the amount of wear, to overcome the retardation due to wear.
This is obviously only speculation!
Same as using a choke on a Petrol engined vehicle, Diesels advance the timing for smooth running when cold.
Does it fill the road with white/blue smoke and your eyes bleed when you get a face full?!  :lol:

[Vincent Waldon]

You're sure you timed it with the cold start lever pushed in?

Andrew

2X.

[kvcuijck]

I can assure all of you () the cold start lever was pushed in before timing the dieselpump.

@Mr Brick-Yard: That sounds like a reasonable explanation. But if the fuel leaks past the piston inside the dieselpump, why is this most obvious when the engine is cold or partially cold? Are there some parts in the dieselpump that expand when heated up and get a tighter fit? (So the initial loss of "pressure" is made good after a while.)
The comment about the smoke you make is spot on. It does fill the road the first few miles....

Next month (after moving house is finished) I'll go and put the timing back to the wrong setting (of 1.4) and see what happens on cold starting and fuel economy.

Does this "tale" not sound familiar to anybody?

[Baxter]

I get lots of T3's with the same problem, I usually over advance them and it helps a little.
I also get lots of 2.4D 5 cylinder T4's that do it too, you change the cam belts and set it up stock and they run like pigs.
The strange thing about a T4 though is the fact that even at higher revs and when warm pulling out the cold start lever does give a mraket increase in power, and it's not just one I have driven that is like that.

[Vincent Waldon]

Hmmm... you've really narrowed it down....


Grasping at straws: cam timing is bang on as well ?

[kvcuijck]

@Vincent Waldon: You're not going to find that straw in the haystack Used the cam locking tool setting up the timing belt and x-checked again when timing the dieselpump. To be 100% sure the second check was done by somebody else... (Good thinking though!)

@Mr Brick-Yard: Your vision and practical experience on the problem sounds very plausible. I'm going to advance the timing and if that will do the trick I'll try and find another pump that will time within spec. Then get the old one measured at a test facility to get things 100% clear.

I just want to get to the bottom of this...

I'll keep you all in the loop and thanks for the help so far!

Koen

[jtanguay]

sounds like the P/O advanced the timing to 'disguise' a big issue like low compression...  or when you timed the engine you somehow disconnected a few glowplugs?

when i had 3 bad glowplugs and one good one, my car started on first 2-3 cranks as well.  means nothing.  but it idled like total crap until warm.  with the gp's fixed she cranks over 1st spin like a champ.

pray that it is just the glow plugs.  another sign that it is the glow plugs, is that the engine will start fine when it has been warmed up.  (but could still have low compression...)

these engines can run for quite a while with low compression.. ask me how i know  :lol: just means you need a perfect gp system, battery, and starter.

[kvcuijck]

Mmm, bad compression is possible though I replaced the head gasket half a year ago and everything ran fine. (Without having changed the advanced timing.) Fuel mileage was good. About 5l every 100km's.

Then I wanted the timing to be perfect....

If it would be the glowplugs, 30 seconds after cold start it should run normal I would think? Glowplugs only help to get it going I thought?

I'll check the gp's as well!

Koen

[shrekaddy]

I  have a aaz doing the same my timing is set to 1.0 and it smokes the street out every morning and delivers really poor mpg  :cry:  :cry:  :cry:

[kvcuijck]

Small update: (no real work done yet)

I've been driving the last 1000km's with the cold start lever pulled (advanced timing). This gives me a smoother run and a lot better economy. (Around 1 ltr to 20km's equals 47 US miles to 1 US gallon.)

This is what I am aiming for. Although the pump is set to 1mm timing, it seems to give me retarded fuel injection. (Probably because of age/tear/wear.)

Also did some background information search and found the following on wikipedia under the subject "diesel engine":

===

"Likewise, when starting from cold, the engine's combustion efficiency is reduced because the cold engine block draws heat out of the cylinder in the compression stroke. The result is that fuel is not combusted fully, resulting in blue/white smoke and lower power outputs until the engine has warmed through. This is especially the case with indirect injection engines, which are less thermally efficient. With electronic injection, the timing and length of the injection sequence can be altered to compensate for this. Older engines with mechanical injection can have manual control to alter the timing, or multi-phase electronically-controlled glow plugs, that stay on for a period after start-up to ensure clean combustion—the plugs are automatically switched to a lower power to prevent them burning out"

I also found this in the same article:

"Advancing the start of injection (injecting before the piston reaches TDC) results in higher in-cylinder pressure and temperature, and higher efficiency, but also results in elevated engine noise and increased oxides of nitrogen (NOx) emissions due to higher combustion temperatures. On the other hand, delayed start of injection causes incomplete combustion, reduced fuel efficiency and an increase in black exhaust smoke, containing a considerable amount of particulate matter (PM) and unburned hydrocarbons (HC)."

===

I always thought retarting the timing would make the engine more fuel efficient. Does somebody know where I can find some more background information on this subject? I'm really eager to get into the details. Just because I want to know!

Regards,

Koen

[kvcuijck]

Hi there,

Last month I've ordered a "timing-kit" so I could double check everything myself. Today I gave it a go and discovered the problem of the bad running engine.

Although we had checked the timing twice when setting it a while ago, today I discovered the timing was set to 0.65mm with the cold start lever to normal. (With cold start pulled timing was set to 0.91mm.)

Today realigned / timed the pump and it now starts without a hitch in cold condition without using the cold start lever. Problem seems to be fixed...

Thanks for all the support I've received! I feel a bit ashamed because it was an (easy to fix) timing problem in the end.... (Seems like we have used some faulty tools.)

Regards,

Koen

P.s. Discovered also this afternoon that the cold start lever advances timing between 0.25 - 0.30mm.

[Tony2ltr]

Ok, first let me start off by saying I have the same problem with a overhauled 1.6 turbo engine I just installed in my 92 ecodiesel. I did my best with the IP timing, but i did not have the proper screw in dial indicator, and used a mag based DI with an extension, but had the cam locking tool.  I tested all my plugs before installation, but not my injectors. I start the engine, and it will run on all 4 for about 10 seconds, then starts to misfire (in cold weather it is worse by far) If I rev the piss out of it, I can clear it out. or I can let it sit for about 4 minutes, and the misfire starts to contribute, and the real bad smoking stops. Now, let me also say that if i don't use the timing advance pull, it will take a really long time to stop misfiring and really run like crap until it is warm.  what is different is that I have my fuel screw cranked in about 1-1/4 turns, running my boost up to about 26 psi, near 30 on a highway pull. so yeah, it smokes all the time under load, because I am running an NA pump. but once warm, it boogies.
From reading the last post it seems like I should go back and check my IP timing again.  Everyone agree?
 Oh, just a little bit of insight, when an engine runs higher advance, the cylinder pressure goes up, this is what creates higher Fuel Economy, because there is more energy released during combustion. UNfortunately NOx is the big problem with diesels, it is when O2 and N2 from the air get squeezed together with the heat and pressure of combustion. Nox contributes to photochemical smog and ground level ozone which is really bad for people. Turbos (especially at 25 psi) make this problem worse.
...Unless you have water injection!!...  :wink:
Thanks guys,
Tony