cold start, sh** happens

[ignas]

hi, vw diesel fans    i have a cold start problem with my '90 vw golf 1,6 eco-diesel. When i start engine after a night it fires with a one crank of starter. But at first in seems that engine works with only three cylinders. After a short time it starts to work normally, with all cylinders. If a stop engine and start in again it starts normally (all cylinders work). And later that day engine starts perfectly and the car goes just fine. But when i leave it for a night and start it another morning, again the same problem...  Glow plugs are ok, compression is perfect, timing is also ok, so what can i blame for that issue? Maybe fuel pump or nozzles?

[burn_your_money]

Glow plugs are ok, compression is perfect, timing is also ok, so what can i blame for that issue? Maybe fuel pump or nozzles?

You are on the right track. Are you sure all 4 plugs are still good?

[ignas]

You are on the right track. Are you sure all 4 plugs are still good?

Yes, i'm pretty sure. I have measured the resistance on each of them. On each plug it was ~1.5 Ohm, according to the vw manual i have, it is the resistance of a good glow plug.

Or maybe a weak accumulator can be a reason? All ground points seem to be good.

[saurkraut]

Might be one injector has a less than excellent spray pattern when its stone cold.

When i test injectors, I always put them in the freezer for an hour befor testing so i can observe their cold spray pattern.  Even some brand new injectors fail at low temps.

Go figure...

[carrizog60]

how do i measure the resistance in the plugs?

[ignas]

Might be one injector has a less than excellent spray pattern when its stone cold

ok, let's say one injector isn't working propertly, but how then explain the fact, that if after first start engine works about 8-10 seconds, then i stop and fire it again, and after that it works just fine?

how do i measure the resistance in the plugs?

remove the conductor strip with which glow plugs are connected together. Then take the multimeter, connect one it's wire to the top of the glow plug's and the other somewhere to the ground. It's simple  :wink:

[935racer]

I don't find that a resistance check is always reliable for testing glow plugs, pull them out and and make sure they all light up evenly and quickly. Or to save yourself some time pull your injectors, check the spray pattern and breaking pressure and check your glowplugs with them still in place.

[wyldman]

Most likely a sticky injector.

A bad glow plug might do it,but usually that cyl will start to fire after 4-5 secs or so.

A bad injector will do it longer.

My 92 1.6 NA does the same thing every once and a while.A few heavy doses of injector cleaner seems to fix it,but it always comes back a few months later.

If you can,start the car,and quickly start cracking injector lines one by one,until you find the offending cylinder.You can then swap injectors with another one from another cylinder.When it happens again,see if the miss moves to the cylinder you swapped the injector to.If it does,then the injector is sticking.If not,then it's something else,either a glow plug,or a compression problem.

[Vincent Waldon]

Did you test your compression while the engine was warm or stone-cold ??

Sounds silly, but I've had two engines now with great compression... when warmed up as per the Bentley instructions.  However, when stone-cold (ok I'm in northern Canada so that is cold) the compression test showed all cylinders lower, as expected, but one really low... aha... there's the problem.

Never really got a good explaination as to what would change s with temperature to effect compression so dramatically... but rebuilds confirmed there was something going on.  The clue was it only happened in the morning, and only in the winter.

Just a thought...

[Op-Ivy]

Did you test your compression while the engine was warm or stone-cold ??

Sounds silly, but I've had two engines now with great compression... when warmed up as per the Bentley instructions.  However, when stone-cold (ok I'm in northern Canada so that is cold) the compression test showed all cylinders lower, as expected, but one really low... aha... there's the problem.

Never really got a good explaination as to what would change s with temperature to effect compression so dramatically... but rebuilds confirmed there was something going on.  The clue was it only happened in the morning, and only in the winter.

Just a thought...

The cold temperature makes things shrink. When it comes to a high pressure, like the pressure inside a cylinder, a small difference in the size of pistons and seals WILL make a noticable difference.

[Vincent Waldon]

Yup, all kinds of things shrink when they are cold !!

I just never really figured out what it was on those engines... rings ??  A sticky valve ?  

And, like the OP, whatever it was staightened itself out with about 30 seconds of normal running... often I could just rev it a couple of times and suddenly all 4 cylinders were engaged.  Restart it and all was good as well.