The cold start valve (ALH)

1. what does it do?

2. What does it look like/where can I find it on the IP?

3. How can I test if its working?


I have a bit of a cold start problem in temperatures below -10C. I have already checked the usually suspects..
Replaced:
4 GPs (due to CEL)
GP harness (due to CEL)
coolent temp sensor (due to CEL)
..these helped a lot with getting decent starts up to -7C, use to be much worse.

fuel filter
injection timing set at 50-55
cleaned EGR valve
new fuel filter
diesel purge
OEM Battery

What makes you suspect the valve?

What is the car doing during the hard cold start?

Cranking slowly - battery issue

Cranking fast but no fire - GPs not on long enough? Can be adapted.

Really need more info on the hard cold start to help.

cold start valve advances the timing for, er, cold starts.

greenskeeper said:

What makes you suspect the valve?

What is the car doing during the hard cold start?

Cranking slowly - battery issue

Cranking fast but no fire - GPs not on long enough? Can be adapted.

Really need more info on the hard cold start to help.

Click to expand...

http://forums.tdiclub.com/showthread.php?t=166760

I have a video of my cold start problem on youtube.com in the above link. I have a new battery and plenty of glow, cycling them helps very little.

Take 110v 3 strand wire, connect each of the three wires together at each end. Directly connect the GP harness at the 4th cylinder to the positive of the battery. Hold for 30 seconds. Have someone start the car after the 30 seconds. If it still fails to start your up a creek.

Your 2nd video sounds like a diesel engine trying to start in the cold without enough glow, or 1 or more failed glowplugs. You can even hear it smooth out gradually as the cylinders get heated sufficently from the combustion after the hard start.

I counted 10 seconds from the GP light coming on until the engine was cranked. The GP time delay can be adapted through vagcom to be on longer...this is why I suggested the direct power to the battery for 30 seconds.

Good luck.

hey im no expert but i was told before to disconect the coolant temp sensor wiring plug, this will default your glow plugs to the maximum glow time 20 sec i think see if this helps .. will only help if your glow time is not quite right if this works take greenskeeper advise and use vag com to adapt... oh bewarned it make the dash flash up coolant bla bla bla ,,, but this will go after a few startes with it conected again

Bs

I would like just to make a comment.
The guy asked a simple question about the cold start valve (location, function, troubleshooting ).
So please guys, if you have no clue about the exact answer to a simple question just STFU. Please don't pollute the thread with BS.
This way the entire forum looses its real purpose.
Its not ment for some self titled "mechanics" opinion. Write something if actually know the matter, if not, just continue watching porn and shake.

Thank you in advance!

ghitaboamba said:

I would like just to make a comment.
The guy asked a simple question about the cold start valve (location, function, troubleshooting ).
So please guys, if you have no clue about the exact answer to a simple question just STFU. Please don't pollute the thread with BS.
This way the entire forum looses its real purpose.
Its not ment for some self titled "mechanics" opinion. Write something if actually know the matter, if not, just continue watching porn and shake.
Thank you in advance!

Click to expand...

First, this thread is ten years old.

And B, I didn't see anything in there but helpful advice.

Care to mention what what part of the thread got in your craw?

A newbie saying STFU to a thread that's been dormant for ten years. Really?

ghitaboamba said:

I would like just to make a comment and that is that I have nothing relevant to say.

Click to expand...

Fixed your post for you. Your welcome in advance.


Must be a Vortex transplant. I'm surprised he didn't jump all over the OP for not asking something important like why do my axles rub on my lowered car or how do I cant the rear wheels?

UhOh said:

A newbie saying STFU to a thread that's been dormant for ten years. Really?

Click to expand...

It makes for good entertainment, if nothing else.

The fun part of this thread is that what VW called the "Cold Start Valve" is actually not a cold start valve at all, and has nothing to do with cold starts.

This thread went off the rails right from the beginning, and post #3 is incorrect.

I call Fake News on all of it.

For the sake of serious searchers I will try to answer the OP's questions.

It is located on the bottom of the pump. Seems to be misnamed; maybe something lost in translation. It controls injection timing.

Maybe VCDS can cycle it? Or observe injection timing on VCDS while varying RPM. In Measuring Blocks, not the timing graph.

It's called the Cold start valve because on the mechanical pump cars, there was a cold start lever and that would move the timing piston when the driver pulled the knob on the dash for cold starting.

It's kind of like how VW calls the VNT a wastegate. It's old terminology for something.

It's been a long time. Isn't the timing advance lever on the top on mechanical pumps?

Don't they also have the hydraulic timing piston underneath?

KLXD said:

It's been a long time. Isn't the timing advance lever on the top on mechanical pumps?

Don't they also have the hydraulic timing piston underneath?

Click to expand...

Sorry I can't answer that question since I posted just about all I know about those pumps in my previous post.

KLXD said:

It's been a long time. Isn't the timing advance lever on the top on mechanical pumps?

Don't they also have the hydraulic timing piston underneath?

Click to expand...

Cold start valve cannot be accessed without pulling the ip. Also new they are quite pricey.

Even IF they're expensive I'm thinking that they're still cheaper (couple hundred bucks?) than a brand new IP or a rebuild. I'm curious, though, what behaviors does a known bad/failing/failed one exhibit? If there's certainty in diagnosis and repair then the cost could be worth it.

UhOh said:

Even IF they're expensive I'm thinking that they're still cheaper (couple hundred bucks?) than a brand new IP or a rebuild. I'm curious, though, what behaviors does a known bad/failing/failed one exhibit? If there's certainty in diagnosis and repair then the cost could be worth it.

Click to expand...

The timing will be off the VCDS chart and when you try to physically retard the timing. You can't. It stays advanced. Then as you physically retard it. It quickly becomes to retarded and won't start.

UhOh said:

Even IF they're expensive I'm thinking that they're still cheaper (couple hundred bucks?) than a brand new IP or a rebuild. I'm curious, though, what behaviors does a known bad/failing/failed one exhibit? If there's certainty in diagnosis and repair then the cost could be worth it.

Click to expand...

$339 bucks. I think failure rate has been very low. I don't think I'd replace one...for that money, and having to remove the pump, I'd be installing another pump. I'd guess, that typically...by the time an N108 fails, a pump would be well worn anyway.

http://www.dbwllc.net/product/028906283m-n108-injection-pump-advance-solenoid/

dweisel said:

The timing will be off the VCDS chart and when you try to physically retard the timing. You can't. It stays advanced.

Click to expand...

Yes...I believe N108 typical failure is stuck open, in which case the advance piston gets full fuel pressure and pegs the injection timing at max advance.

DBW did a nice write-up, and has it as a downloadable PDF at the bottom of the page linked above.

For some reason I seem to recall finding something for closer to $200, but apparently I'm mistaken: I'm always stuffing bits of trivia in my head in case I need to pull something out when I run across a scenario that sounds "familiar."

Here's another thread that provides good information (the N108 is referred, here, as "Commencement of Injection" valve):

http://forums.tdiclub.com/showthread.php?t=273503

UhOh said:

Here's another thread that provides good information (the N108 is referred, here, as "Commencement of Injection" valve):

Click to expand...

That would be a better name for it than Cold Start Injector or whatever it is called. Better name(s) would be...Commencement Valve, or Start of Injection Valve, or Timing Advance Valve, etc, etc...

I had an N108 fail and fault out one sunny Saturday morning. Engine sounded like a John Deere. Low power. Went straight to the shop and swapped in a used one in about an hour. Old n108 was open circuit.

That was like 5 years and probably 150,000 miles ago. So n108 failure doesn't correlate well to pump wear or outright failure.

Did you investigate? Busted wire or deeper in?

How many of you that had IDI's drove around with the start knob pulled out all the time?

I did.

Folks, check the date on the first post in this thread, and find the post that resurrected this thread from the abyss.

It is time to allow this thread to return to the abyss from which it came.