Cold Start Issue

[mike_low3]

Hello there,

New to the forum and just wanted to ask a question about my 2002 Passat 1.9 TDi (130). I'm having problems getting the car started and this seems to be especially worse when the weathers cold, this only happens first thing in the morning after the cars been sitting all night.
Basically you try to start the car and the engine turns over 2/3 times then almost starts but then dies, no warning's or lights, you then try and start the car but it just turns over and it takes almost 30-40 secs of this before your fell the engine start to catch then it starts, quite a bit of black smoke then comes out the exhaust.
The car was in the garage for this fault 3 weeks ago and they replaced the engine coolant sensor (diagnostics said this was faulty) and all 4 glow plugs as they said they were all faulty, which confused me as the car would start eventaully ? After the car came out of the garage everthing seemed ok until last week when this fault started showing again,
A mechanic friend has recommended maybe adding a diesel fuel additive as he thinks the injectors could be dirty or clogged, could this make a difference, I'm now starting to think this could be a fuel issue, any advice would be great

[SONICtheONE]

What condition is the battery in, It might be a good idea to get the battery drop tested, it might not have the cold cranking amps it needs.

[mike_low3]

Never thought of the battery ? I just assumed that as the engine was turning over that the starting motor etc was getting power, can a garage check the battery ?

[bakili]

I have same car , same problem my car would not start cold morning, from first time. I changed glow plugs, diesel filter, did not help much. Scanned for faults and engine speed sensor, cleared fault. Fault still not come back, car starts fine now. I don't know possible its warm mornings.

[adamss24]

I would guess its air in fuel or a duff engine coolant temp. sensor. If the battery is weak, it wont last 30-40 sec. of cranking ! Prolonged cranking will also destroy the starter motor as well...

[snapdragon]

I would say fuel is draining back to the tank overnight due to a leak allowing air in at the engine end. When it starts and you turn it off straightaway, will it restart again immediately even though it is still stone cold? If so, this makes it less likely to be temperature related or a fluke that it started. Try sniffing for a hot diesel smell around the engine at the end of a journey.

[mike_low3]

The engine coolant sensor has been replaced along with the glow plugs, problem still happening. When it starts first time I can switch it off and it will start again no problem every time, as I said before this problem is more evident on cold mornings, when the weather is mild it starts first time no problem, which has me thinking I have duff cells in the battery ? Even when it's cold and I eventually get it started, if you turn of the engine it will start first time again no problem, just getting it initially started is the problem.

[Col]

I agree with Snapdragon.

Sounds like the fuel system is not sealed properly, air is getting in allowing the fuel to drain back to the tank.

What your car is doing is bleeding the fuel system every morning.

To cure would be a process of elimination. starting as near to the injectors as possible and working back towards the fuel tank.

The prime suspects if I were looking to remedy this would be;

Fuel filter connections, particularly the fuel stat that presses into the top of the filter. This has two 'o' ring seals that must be replaced when renewing the filter (you get these when you buy a filter)

or

The tandem pump. This both is a vacuum pump (for the brake servo and turbo) and a fuel pump.

or

Any of the pipes, hoses and connections on the flow and return to the tank / pump / filter. Tricky to find and the only real way to do this is to replace the hoses.

[snapdragon]

If it doesn't do it on milder mornings, maybe a seal is leaking only when below a certain temperature due to hardening or metal contraction then.

A failing battery could be the problem as others have said, the engine has to crank at a certain RPM before a diesel will start, because of thermodynamics, if the engine is too cold it won't start (hence glowplugs) and if it cranks too slowly, the peak cylinder pressure's increase in temperature will ebb away leak into the stone cold block thus reducing the compression pressure to.

Also, you shouldn't need glowplugs to start these cars in temperatures above ~0˚C - they do still come on though to reduce noise and emmissions and stay on for 3 minutes after the car has started.

[mike_low3]

Cheers for the replies, but my suspicion's have been confirmed about the battery, tried to start the car on saturday and the battery was completely dead, car was fine on friday. Got it jump started and is running fine but I've now bought a new battery, will fit that tonight and keep and eye on things.