A3 BLS 1.9 occasional hard start when cold

[Evman]

Hi, long time reader, first time poster.

I have a problem with my 2009 1.9 BLS tdi, where occasionally it takes 20 or so seconds to start in the morning. Initially there seems to be no combustion, then after a few seconds sounds like it wants to go, then finally it starts, but fires up perfectly, with no roughness, spluttering or smoke, instant perfect idle. Normally it starts just by touching key, including if I shut it off immediately after having the issue. The engine runs perfect, smooth, no smoke, basically perfect, but does have 140000kms.

It seems to only happen if left for a few days, maybe once a week, but the problem seems to be more often now the temperature has dropped, although it’s was still doing it when around 16 degrees. I thought it could be the battery as seems to happen less with long drives (and battery was getting old), so have replaced it, but it happened again, although was quicker to start this time (faster turnover?).

I get no errors using VCDS.
I’ve tried running the fuel pump via VCDS for 30 seconds and made no difference.
I’m wondering if it could be a sensor failing?

Does anyone have any ideas? Are there any values I should compare with VCDS when it’s starts vs when it won’t?

Thanks for your help.

 

[Nessy]

First thing I’d do is change the glow plugs.
Mine became a poor starter ( it would fire but run roughly for a few seconds) and changing all 4 glow plugs transformed the way it started, even in summer.

 

[Evman]

First thing I’d do is change the glow plugs.
Mine became a poor starter ( it would fire but run roughly for a few seconds) and changing all 4 glow plugs transformed the way it started, even in summer.

there is no rough running at all, and it will still start on freezing mornings most of the time as soon as the key is turned. I think glow plugs would be a consistent issue?

 

[Evman]

Ok, update. This morning wouldn’t start at all, plenty of turn over speed, but not a hint of firing up. Probably tried 5 times. 2 days in row is a first. 5 degrees this morning, has started on colder days. So pluged in VCDS, no errors. Fuel, air and coolant temp sensor showed around 10 degrees, so seem to be working. I then gave it another try, and after about 10 seconds of cranking, started to sound like it was wanting to go, then it fired up perfect, no smoke, no rough idle.

Could a glow plug relay issue cause this? Maybe works sometime, not others. Although it has done this in warmer temps too, say 16 degrees.

Thanks

Edit: checked glow plug resistance, the all read about 0.5 ohms.

 

[Daveyonthemove]

Could be an air leak in the fuel system causing pressure to drop.

 

[Evman]

Could be an air leak in the fuel system causing pressure to drop.

Any idea how I could test that?

 

[JimS3]

Yes, change the fuel hose going from the fuel filter to the engine (feed, not the return) for a piece of clear hose, then check for bubbles when it is hard starting.

If you have VCDS check the rpm too when cranking, as I believe the engine needs to see around 280 rpm to begin adding fuel. (possible lazy starter motor)

 

[Evman]

I checked the rpm in VCDS when in happened and it was 253 rpm, but the ECU was asking for fuel to be injected looking at measuring block 001 and 004.

I’m going to get some clear fuel hose and see if that shows anything. Might even put a check valve in.

 

[SootySport]

I would also think of glow plugs causing this problem. At 140K Kms. they would be due for a change anyway. Other things to check are water in the fuel and the fuel filter.

 

[paddy]

Three things spring to mind
1/ its pumping up compression with fuel before it can fire ?
2/ I think the high pressure fuel pump is belt driven on these engines and is not getting the pressure up at cranking speed.
3/ My vivaro did exactly this and it was injectors. Ran perfectly once it started but anything below 10 degrees C and it just wouldn't fire up without a squirt of easy start. Try a can of easy start from halfords