Cold start issue

Hi, did a search but couldn't find much. I've noticed (pls click here for video) that as of recently my MKV PD 1.9 Jetta 2007 TDI engine has been requiring more cranking to start when cold. When the engine is warm, there's no issue whatsoever; the colder, the worse.

The battery is relatively new (18 months since I replaced it), so I don't think that's the issue. I plugged in a VCDS-like cable and noticed one of the spark plugs is throwing a generic error; from another post, I was left with the understanding that even with one spark plug working, starting the engine should not be an issue.

Thank you for your input.

You haven’t got any spark plugs. You’ve got glow plugs, how cold is the temp outside when it is slow to start?


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kdawg89 said:

You haven’t got any spark plugs. You’ve got glow plugs

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I meant glow plugs

kdawg89 said:

how cold is the temp outside when it is slow to start?

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Not that cold really: 10°C/50°F. Issue happens whenever the engine is NOT warm (p.e, after having the car sitting at the office parking lot before heading back home). When the engine is warm, it turns on just fine.

Does it run and drive well once it’s running?

I can’t imagine 1 failed glow plug causing that issue at 50 degrees but maybe if none of the glow plugs are working due to a relay or something.

If it starts great when it’s warm it very well could be glow plug related especially since you have a code for something glow plug related.

I can’t think of anything else that would cause that hard of a cold start but then allow the car to drive fine.

What if you shut the car off after say 10 seconds and try to restart? The fuel system could lose its prime after sitting for awhile which would make it seem like a it is because the engine is cold but is actually a function of time sitting for it to depressurize, I think there might be a check valve that keeps it pressurized.




Edit: see post 11 here. http://forums.tdiclub.com/showthread.php?t=320716

The check valve is in the tandem pump but some people just put an in line check valve in to should having to replace the tandem pump.

Found the problem...

kdawg89 said:

I can’t think of anything else that would cause that hard of a cold start but then allow the car to drive fine.

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Found the issue: need to replace the harness.
Connected a VCDS cable and this error code came up:

On inspecting the glow plugs, not only noticed the harness is in really bad shape, I did confirm that indeed the connector to one of the glow plugs was broken.


Will buy one and will report back in a few weeks from now. Hope this fix the issue.

foliva said:

I meant glow plugs
Not that cold really: 10°C/50°F. Issue happens whenever the engine is NOT warm (p.e, after having the car sitting at the office parking lot before heading back home). When the engine is warm, it turns on just fine.

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10°C is not that cold for a PD.

Check out the glow plug time on our engines:



Possibles reasons, ECT is throwing a value a lot higher than ambient temperature, losing fuel overnight on the head/injectors/tandem pump, low compression.

k_pt said:

10°C is not that cold for a PD.
Check out the glow plug time on our engines:

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What is that chart even showing? What does air presure have to do with glow time? It was in the mid 20F's the last few days and 2 or 3 seconds is all mine needed to start.

atikovi said:

What is that chart even showing? What does air presure have to do with glow time? It was in the mid 20F's the last few days and 2 or 3 seconds is all mine needed to start.

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Atm pressure.

replaced glow plug harness and check plugs... little to no improvement

foliva said:

Found the issue: need to replace the harness.
Will buy one and will report back in a few weeks from now. Hope this fix the issue.

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Quick update: had the harness replaced with a new one (USD 80 parts and labor). The error is gone but unfortunately little to no improvement (click here for the video of morning start day after I had the glow plug harness replaced).

I checked the plugs with a multimeter at the lowest resistance setting (200) and all four consistently read 1.3. So I guess the plugs are not the issue.
Scratching my head here...

k_pt said:

10°C is not that cold for a PD.
Check out the glow plug time on our engines

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Thanks... how would I need to go about doing this?

Had the same issue it’s a crank shaft Position sensor have them check that


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Change fuel filter

tdiman said:

Had the same issue it’s a crank shaft Position sensor have them check that


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Thanks... where you getting an error code associated to the crank shaft position sensor? Because in my case the only error I had was related to the open/broken glow plug harness connector (which is now gone).

Fuel filter?

bbexotics said:

Change fuel filter

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Thanks... is there any way to check if the filter is the issue without having to replace it? Perhaps if I have it cleaned somehow?

The car has on the odometer 174k kms (108k mi) and I had it replaced at 150k (93k mi); I'd image it'd still have some life in it?

I had one of my 2 BRM Jettas cranking forever to start and I replaced the glow plug harness, injector wiring harness (under the cam cover), in-tank lift pump and the tandem pump. I also replaced a few of the shorter fuel lines because they were old and cracked (I made my own lines). It will start on the first half crank now even when it is zero Fahrenheit. My other Jetta starts on the first half crank as well. Your fuel filter should be good for 20,000 miles unless you got a tank of bad fuel that clogged it.

Fuel tank pump fairly clean... must be something else

bbexotics said:

Change fuel filter

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The fuel filter has only 24k kms (15k mi) in it, so I'm pressed to believe, me thinks, that that is not the issue.

For what is worth I checked the pump inside the fuel tank. The mesh/screen inside came out fairly clean; certainly not clogged:





I had it cleaned regardless with a brush and diesel: