Cold start issue on ALH

Hello All. I wonder if you have any suggestions on this one.
I have a high mileage 2001 ALH (5 speed). It got down to 0F last night and the car was outside and I wanted to test start it at those temps and preheat it a little for my daughter. It is driven daily.

I have 8 oz Power Service when I filled it (half tank now)

The car started on the first try, with some cranking and the accelerator pedal floored. (I was impressed) so I let it idle for 10 minutes or so to warm it for easy starting later in the day and shut it off.

We tried to use the car 5 hours later (when it was 12 F outside) using the same floored accelerator technique with no ignition or sputtering at all. I warmed the fuel filter and pump by trickling (8-10 gal) hot water over them, thinking fuel was gelled l in the filter or wax had clogged it (although the Power Service should be sufficient to below zero, I thought)

I took the thermo-tee out of the filter to suck out a little fuel to make room for Power Service 911 (probably only an ounce - not enough probably). The fuel looked to be liquid but I did not look inside with a flashlight. Still no start after significant charging of the battery and cranking. I bled the fuel line at the top of injector #3 thinking priming was lost, and it seemed to bleed fuel into a rag. Still no ignition or sputtering.

2 Questions.
Is 8 oz of Power Service enough for temps like 0 F?
Is there a chance that my thermo-tee is stuck open and i filtered all the wax out of my tank and clogged the filter in 10 min of idling?? Do they commonly fail?

Any other ideas of why I could start at 0F early in the AM and not start later in the day at 12 F? I did not check glow plug function but they were obviously working in the early AM.

Thanks
Chuck

Update

I let the battery charge for about 2 hours and just went out to try it. After some extended faster cranking, it sputtered one cylinder at first eventually fired up! It seemed like I needed to prime the pump. No white smoke. Burned clean (so I am thinking glow plugs are OK but was not getting fuel) I ran it around the block a bit and no loss of power. It is 12 F at the moment.

Does this make sense?
Is this just cold weather rubber shrink/old hoses to cause a loss of prime after 5 hours? We have had no issues starting in 12 mos.

Could this have been wax/gelling and my hot water/PS-911 eventually worked?

If the glow plugs were dead, would it ever start at 12 F like it just did?

Now that it is in the garage, I can do more diagnostics.

Ideas welcome. Thanks. Chuck

First off, even if the Thermo T is working properly (brand new), there is always some fuel being pulled from the tank. The unused/left-over fuel, which has been warmed by the engine, is dumped back into the fuel filter.

I'm guessing that 5 hours allowed the engine to cool down to the 12f ambient. And, the fuel filter cooled much, much faster.

So, I believe your starting issue was just cold related in combo with the IP suction pulling in some air around the O-rings at the Thermo T due to possible waxing in the filter while the engine was idling. Remember, that fuel was hitting the filter element at 0 f.

Just a wild guess ...

As I stated in another Thread, the IP has the ability to create enough suction (vacuum) to collapse a fuel tank (happened to my brother's 84 Jetta Diesel... no doubt at all). So, in my opinion, the Thermo T is the weak link in the fuel system with respect to allowing air in!

For a good cold start TDI you need:

1. Injection timing set within bounds (might be worth checking with VCDS).
2. All 4 glow plugs operating well, full GP cycle & wait 5s after glow plug light goes out (it’ll start on less than all 4 but it won’t be pleasant)
3. Good fuel.
4. Strong battery. If you’ve cold started you will need to let that battery charge. A good indicator of the health of the battery is measuring the voltage during a cold crank situation. Needs to above 11V to be successful.

A couple points:
1. ALH is drive by wire, holding down the accelerator does nothing for starting.
2. 12F isn’t that cold, with everything maintained and operating well I’ve had successful cold starting in -40.
3. A couple cold starts without a good run to charge the battery won’t help you out.
4. Any CEL? What code?
5. I’ve found significant improvements in cold starting after ditching the factory GP harness & making my own out of 12ga wire, ring connectors & tapped the top of the GPS.




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If you were having fuel prime issues you would see lots of large bubbles in the line at the IP. What did you have?


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Hi Andy,
Thanks for the input. Thinking about that vacuum, I do seem to recall slight inrush of air into the filter when I pulled the Thermo T. I am not sure if that was just siphon action back to the tank or a vacuum lock.

If the Thermo T was stuck open, it would grab more wax from the tank right? And it would not have the advantage of warming recirculation.

I dumped the rest of the bottle of PS-911 into the tank.

The current filter is pretty old (from prior owner) and dull showing age. I have a new filter on the shelf. I think I am going to get a new Thermo T and swap them out.

ScottySK, how far back toward the GP Relay did you run the 12 gage wires? And, if you spliced, did you just crimp them or soldier?

I agree about the Drive-by-wire thingy, but if the engine begins to catch (start) while cranking and the RPMs go up (just for a split second) it would seem that the ECU would sense the additional pedal. Of course, the Temp sensor is telling the ECU that it is darn cold at 0f, thus should increase the fuel quantity while starting........

Yeah, everything needs to be spot on for a good start when in the single digits and below 0. I've not tried my Jetta but the 5.9 Cummins fired this morning at 3f.

AndyBees said:

ScottySK, how far back toward the GP Relay did you run the 12 gage wires? And, if you spliced, did you just crimp them or soldier?

I agree about the Drive-by-wire thingy, but if the engine begins to catch (start) while cranking and the RPMs go up (just for a split second) it would seem that the ECU would sense the additional pedal. Of course, the Temp sensor is telling the ECU that it is darn cold at 0f, thus should increase the fuel quantity while starting........

Yeah, everything needs to be spot on for a good start when in the single digits and below 0. I've not tried my Jetta but the 5.9 Cummins fired this morning at 3f.

Click to expand...

I didn’t go all the way to the fuse box. Double crimp on the splice & ring connectors. I’d get a monthly glow plug CEL before & haven’t had one in 18 months since.

I don’t believe the ECU registers the pedal input until RPM is over 750rpm or something near that.

The 5.9 Cummins will start in any temperature, just need to be patient for that grid heater to do its thing. My dad has a ‘92 with over 800,000 km & it has always started.


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Thanks Scotty. There appeared to be no bubbles in the clear fuel line when I was fiddling with it all. When it eventually fired up, I quickly drove it into the garage just in case it would quit on me. I did not check for bubbles when running. Then I drove it around the block.

I replaced the GP harness a couple years ago with a new OE type.
Lots of good suggestions and good points. Maybe it was poor cranking speed (from the weaker battery) but I had the charger on it while fiddling with it and while not a deep charge, it was giving me decent cranking speed for a few seconds.
Thanks again!

Is 8 oz of Power Service enough?

I've been running both my cars in temps only in the single digits with negative digits overnight. Only one of them has Power Service in the tank, and even then it's maybe a couple ounces. With one exception both cars have been starting every morning.
I think a whole bottle is used to treat a rather large tank, so 8 ounces might be more than enough.
As others have said, you must have a healthy battery, a healthy starter, good GP's, and it helps to have the timing advanced.
Never heard of flooring it while starting, not sure if that'd make a difference or not. It's not carburetted.

2 things.
I thought I read flooring the peddle while cranking stops injecting fuel.
I add 6 oz of Power Service white bottle.
Never had a problem.
Was low teens today and the car started after a few seconds on the 1st crank.
260K miles (US) on the car, original starter.
Battery only 2 or 3 (at most) years old.

Moving the pedal down absolutely does increase fueling. And the manual may even say something about that in extreme cold starting scenarios. Over the years I'll run into having to show new diesel owners how to start their cars in extreme cold, and that is one of the "tricks".

Weak starters on TDIs cause hard cold starts too. These starters rarely just up and die like many other cars. Instead, they get weaker and weaker, and one may not even notice just how slowly they crank until a new starter is fitted if you do not routinely start lots these cars up (like I do).

I am going to repost this reply again seeing as it may very well apply on this thread too.

"Sounds like your problem may be....

If it is fuel gelling it won't be in the engine, it will be in the fuel filter or at the sending unit/pickup in your tank.
Your sending unit/fuel pick-up, that is in your fuel tank, has a very small orifice at a check valve that can and often will bridge/plug with debris, ice, and/or gelled fuel.
When this happens the vacuum created by the inj pump trying to suck fuel will cause air to be sucked into the fuel system at the weakest link, usualy the thermo T at the filter. This all happens more commonly in cold temps.
See....
https://www.youtube.com/watch?v=yRMTEAKsScE
If this is your problem search "ALH TDI blocked check valve in sending unit".
The check valve can be drilled out and removed."

I'm with Oilhammer on adding some accelerator pedal when starting in cold weather. It doesn't require WOT....... just more than at the idle position.

Try it the next time you're starting the engine on a very cold morning.

And, Maxmoo is correct about the IP sucking air into the system! I believe that's the source of bubbles I've seen from day one of owning my 2000 Jetta! At least that air does get filtered.....

I agree, some accelerator pedal but not floored
Mine started very well the other day with the cold.
Usually runs a little rough with white smoke for a short while.

Can someone explain, or direct to documentation, what pressing down on the accelerator does at start?

I don't know if it does anything at all (if the ECU will pay any attention to the throttle position until the engine fires), but if it does it's NOT helpful.

Liquid fuel (no matter what fuel it is) DOES NOT BURN. Period. What burns is fuel VAPOR. The heat of vaporization is required to turn the fuel droplets into vapor and the more of it there is the more heat is extracted from the charge air to vaporize it.

Any more fuel than is required to fire under extreme cold conditions hinders starting rather than helping it because it cools the charge more than is absolutely necessary and if that is below the ignition temperature you get no start at all.

Keep your foot off the pedal and let the ECU do its job.

I've had my '03 in very cold temperatures and it has never had an issue with starting, even when it only had one working glow plug due to a bad harness! It didn't like it very much at all but it started because the first cylinder that fired provided enough additional cranking speed to get a second to light, and so on. Within a few revs it lit up and ran.

The BIGGEST issue with very cold starts and diesels is to make certain that your battery, cabling (including grounds!) and starter are in good shape. The thicker oil reduces cranking speed (bad) and the cold limits the amperage the battery can deliver (bad too!) Between those two if the cabling or starter are compromised in any way you will not get enough RPM for the engine to fire. The other thing is to be DAMN SURE you have NO air leaks in the fuel system because ANY air in the IP's high pressure side reduces injection pressure (the air must compress first) and that makes for a poorer spray pattern which inhibits vaporization as well.

If you've ever owned old mechanical diesels such as Detroits (which have no intake heater or glow plugs at all!) in very cold conditions you know that cranking speed is the holy grail of getting them to fire and that if you hold the STOP button down, forcing no-fuel mechanically at the governor, until you have as much cranking speed as you're going to get you materially improve the odds of being able to light it off when the temperatures get cold. As soon as you drop that button you can actually hear the cranking speed DECREASE.

Genesis, your comments are pretty much as how I thought about all this. However, I always would like to keep the door open for possible other reasons, and I'm not really thinking I'd ever bet against Brian! So...

Could this have to do with the N108, causing to advance more?

In an ideal situation, you should not need to. But (as many of us know), sometimes in extreme cold the engine needs a little help to get going. I've house called lots of these cars, or had them towed in, that were like this.

My own ALH will not start in single digit temps without depressing the accelerator about half way. I could crank the battery flat, it still won't start. But pressing my right foot down a couple inches, and it stumbles to life every time. Little puff of smoke and some normal diesel clatter and I'm off. After 535k miles, if that is what it takes to get it going, then so be it.

Like I said, lots of them are like that.

The PDs have a much better timing advance map for cold starts, as they rarely need any help. They also "nail" a lot more after a cold start, and are pretty lethargic for the first few seconds when cold. But they seem to generally start easier, with less of a preglow period necessary.

And, if your injectors are "putting in" drops, something is bad wrong!

Have you ever seen an Injector in operation (ALH, bench tested or otherwise)? The "injection" while cranking is an extremely small "fog" that has a duration that lasts quicker than a cat can wink it's eye (an old saying).

As I stated previously, in my opinion, once the ECU senses that the starting RPM is "equivalent" to 250 (if that's the magic number), it injects fuel based on a number of parameters (fuel temp, ambient temp, coolant temp, etc.). So, if the accelerator pedal is pushed down a bit, when that first cylinder fires, the next one will have sufficient fuel to fire and so on! The first cylinder firing drastically ups the RPM.

The fueling system of all engines, gassers included, are designed to "increase fueling" during starting in cold temps and until the engine warms up to or near normal operating temp. Hook up your VCDS and observe fuel quantity when the engine is first started and while it begins to warm up. You'll see the injection quantity begin to drop off as the engine warms up.

I've been driving VW diesels 38 years and experienced about every starting scenario imaginable down to about -10f (no, not as cold as farther north). Adding accelerator pedal during very cold starts is how I've always done it after learning it helped. Heck, my 5.9 Cummins liked a little more accelerator during a 3f start the other morning!

Yes, it's a "fog" (very small droplets) but the point stands on the heat of vaporization and where it has to come from as that's a matter of physics.

My method for a less grumpy 0F start....(foot isn't touching the fuel pedal)

Glow once
Crank for a few seconds
Glow again
Crank till it starts....which is pretty quick.

I think my starter is getting weak though. I did the upgraded battery/starter/alt cables and my battery seems strong. I need to follow the starter refresh thread.

Can anyone comment on the possible "theory" that the N108 has a say-so in this?

If the N108 affects timing would pressing down for more fuel effectively be instructing the ECU to also apply more advance? More advanced timing for cold starts is a plus.

For what it's worth, the other night I applied the accelerator on my car, though temperatures aren't cold now, and the engine fired up instantly. My car starts very well all the time (unlike others, however, I am not all that subject to very cold temps, so no real proving ground here). My wife's car has always been a little less prompt about starting- I'm going to try it with that car to see if it has any impact: I have the timing set way advanced clipping the upper line.

UhOh said:

Can anyone comment on the possible "theory" that the N108 has a say-so in this?

Click to expand...

Maybe this will have something.
Light reading anyway.
http://gershon.ucoz.com/BOSCH/DIESEL/pumpsVE/Bosch_VE_Pumps.pdf

I think that you had gelled fuel and when the 911 did it's thing you were golden. the first weekend in Jan I had to fill up my take because it started gelling while driving in Vermont. before I did that I put about 2 gallons of kerosene in first and I haven't had a problem since.

wonneber said:

Maybe this will have something.
Light reading anyway.
http://gershon.ucoz.com/BOSCH/DIESEL/pumpsVE/Bosch_VE_Pumps.pdf

Click to expand...

Glad you posted that link. I had that Doc on my other computer; now it's on this one.

oilhammer said:

Other things beside the glow system can cause a long crank time and hard starts. Poor starter (slower than ideal crank speed), loss of fuel prime (leaky pump), poor nozzle condition (poor fuel atomization), low compression (worn engine), bad temp sensor info (fuel, coolant) to ECU, timing incorrect (botched timing belt install), etc.
That said, with those temps, it is going to have a really hard time starting without some sort of aid anyway. The coldest I have had to start one of my ALHs at was about -20 C, and it took three long preglows and about 5 seconds of cranking, then some coughing and sputtering for a second before it finally lit off. It was not happy. But it DID start. And that is with EVERYTHING in perfect working order.

Click to expand...

oilhammer said:

In an ideal situation, you should not need to. But (as many of us know), sometimes in extreme cold the engine needs a little help to get going. I've house called lots of these cars, or had them towed in, that were like this.
My own ALH will not start in single digit temps without depressing the accelerator about half way. I could crank the battery flat, it still won't start. But pressing my right foot down a couple inches, and it stumbles to life every time. Little puff of smoke and some normal diesel clatter and I'm off. After 535k miles, if that is what it takes to get it going, then so be it.
Like I said, lots of them are like that.
The PDs have a much better timing advance map for cold starts, as they rarely need any help. They also "nail" a lot more after a cold start, and are pretty lethargic for the first few seconds when cold. But they seem to generally start easier, with less of a preglow period necessary.

Click to expand...

Dude man!! Why didn't you mention pressing the accelerator in the other thread ! So think this might help me in the future if i press the pedal down?? Never touched it before ..... or at least worth trying??