2002 Warm Start Problem

Hello everyone,
I have been combing the threads and picking at the brains of all the mechanics I know to figure out this problem, hopefully without spending a load of money. My problem is that my 2002 Golf ALH doesn't like to start when the temperature of the engine is "warm" not cold, not hot, but warm. I had a stretch of -20*C days last week and the car would start great after sitting all night. The glow plugs glowed for maybe 6-10 seconds and then the engine fired up right away when the key was turned. I would drive it until warm, then turn it off. With the engine at temperature, it would fire up no problem. However, if I let it sit anywhere from 1-6 hours, it will not glow, and will not start easily. I have to hold on the starter for anywhere from 5-10 seconds.
I thought at first it might be the Coolant Temp Sensor (CTS), so i checked the live info with a scanner and when the car had been sitting in -10*C temperature for 8 hours, the ECU was reporting 8*C. So I swapped out the CTS with a new OEM sensor. The problem persisted. It has a brand new OEM starter in it, which would supposedly rule out the slow cranking option (where the starter doesn't crank fast enough to ignite). The battery isn't new, but I have tested it and voltage is good.
As of right now, I am having to unplug the CTS pretty much every time I want to start the vehicle after it has sat, and then plug it in before i drive away.
I spoke to the dealer, and they just said "let us look at it for 130$/hour." Yea right. I was hoping someone here might have some insight into this problem. All the other threads I've found are focussed on the 99.5 model year and the hamman mod, or a tune fix.
Anyone have anything they can think of?
Thanks in advance!

Have you checked the injection timing?

Glow plugs can aid a start up with retarded timing. Once the engine temp is too warm to cycle the plugs the engine relies on the compression only and if the fuel is not taking advantage of the heat by being injected too late you will have to crank longer to create the heat.

Get with someone who has VCDS if you do not and get it checked. Then you can fix it or rule it out of the equation.
See the trusted mechanics list at the top of the TDI 101 forum for a guru near you!

Thanks JETaah. I'll get on that asap.

Update:
The continuous laying on the starter tired my starter out, so i replaced it again with an OEM one. Battery was also on it's last legs (reporting 11.00V) so I replaced it with one from VW. With sensor plugged in, engine is spinning around 300RPM (should be good enough to start), but doesn't start easily. When it does, lots of smoke still. Still resorting to pulling the sensor to start.

I'm hoping to check the timing this weekend, I've just had a heck of a time lining up my schedule with my buddies schedule (and it's his computer i'll be using.)

If that happens, hopefully it works.

Finally got around to checking the timing this weekend. The timing was off by a few degrees. It was firing at around 85 degrees, should have been 60. With that adjusted, checked, and confirmed to be dead on, the problem persists. Thinking of checking valve timing (cam timing) next as it seems like there isn't enough compression happening to start. Any further ideas beyond this? Timing belt was done 50,000Km ago.

What's the IQ set at?

Seeing any air in the fuel line?

I've only seemed to read that for non 1999.5 cars that warm start problems are IP issues.

Are there ANY codes being triggered?

Might try ruling out the fuel pick-up, fuel filter and associated lines by connecting a fuel source directly to the IP (like one does for a Diesel Purge treatment).

Interesting idea! i'll give that a go to rule things out. Fuel filter itself shouldn't be the problem, I just changed it 2 weeks ago. Not seeing any bubbles in the fuel line.

No codes are being thrown.

The main reason i was thinking maybe valve timing is off is because when i go to start it now it seems to be spinning faster than usual (faster than it should) leading me to think the valves might be off reducing compression.

Thanks for the ideas! I'll report back with my findings.

Cheers

If it's spinning REALLY fast then check to see if your ASV is closing down on you. "No air" situation will mimic low compression.

Have you tested the actual glow plugs? The GP harness could be getting bad too. Maybe the glow plug relay?

The fact that the car will start when you unplug the Coolant Temp Sensor should be the key? Does unplugging cause the glow plugs to activate even though the engine is warm? If so that would say that:
1- the car starts when cold because the glow plugs activate
2- the car starts when warm when you unplug the CTS so the glow plugs activate (do they?)
3- the car starts when it is hot because the chamber is warm enough without the glow plugs

So why would the engine need extra heat for combustion when it is warm (not hot)?

I think it could be low compression. Are you using 5w-40 oil?

Warning I don't know Jack Manure and I am no mechanic. I'm simply intrigued by the problem you are having. I thought it could be the ASV. I had that problem with my ALH when it was HOT but since your car is warm and starts when you unplug the CTS......

Funguy, yes, you're right. I missed the CTS note.

Really is likely TWO issues here. One is almost certainly the CTS: if BLACK (didn't they have the newer style by 2002?) then replace it! (but it might just be bad anyways)

This may be the first time in 12 years that I get one right! Even a stopped clock is right twice a day (except in the military).

Looks like the OP did change out the CTS in his first post. Could it be the wire or connector?

Problems that are jumping around (and almost contradictory) sure tend to be popular with electrical issues. Most of what I could think of would trigger some code.

I wonder whether this is the original ECU or one swapped from a late model year 1999 car (those had warm start issues- map update fixes).

Went back and re-read. JETaah's post (#2) makes a lot of sense, and I think it might be the best low-hanging fruit approach: generally that's what people should look at from the start- timing.

SilverBulletTDI said:

Finally got around to checking the timing this weekend. The timing was off by a few degrees. It was firing at around 85 degrees, should have been 60. With that adjusted, checked, and confirmed to be dead on, the problem persists. Thinking of checking valve timing (cam timing) next as it seems like there isn't enough compression happening to start. Any further ideas beyond this? Timing belt was done 50,000Km ago.

Click to expand...

Have you checked the integrity of the harness on Injector#3? (if looking at the engine, bonnet up, and ,moving to left... driver's fender to the right, one injector, then it's #3.) It's the expensive one, and also the toughest to get at. It's the 'Needle-Lift' sensor, and seems to control the rest of the injectors...seems silly now. Jus' my 2c...

-M.

Thanks for all the replies guys! I finally figured it out and it is now a solved issue! The problem was whoever did the timing belt last (before my ownership) did not do it correctly. We set the engine to TDC on cylinder 1and noticed the camshaft was not positioned where it should be. So we set the cam to where it should be, locked it off, loosened the camshaft pulley and spun the crankshaft until the engine was at TDC. This along with a new fuel injection adjustment to meet spec fixed the problem! Just goes to show you how important precision is in the timing belt. Thank goodness my engine didn't suffer any damage.

The 2002 does have the upgraded (green four pin) coolant temp sensor, since the originals were recalled.

Again thanks for all the input, I've definitely learned a lot through this 3 month battle.

Cheers