This problem is going to end me

26 Aug 2019
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United Kingdom

I have mk6 golf TDI 2010

At around 100k miles I started having this problem where the car struggles to start. Almost sounds like it's mis firing (it's not a petrol though)

When I start the car it sound like it is running off 3 cylinders but after a short period of time it runs normally.

I have video of it trying to start if anyone would like a challenge and help me with this.

I have had a OBD reader on it and that had me changing the EGR valve but it didn't sort the issue . So I'm completely lost

Any help would be greatly appreciated.
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It sounds like a fuel starvation issue to me.....if the fuel is allowed to return back to the tank overnight this sort of thing happens.
Is there a fuel priming system - a rubber bulb you can squeeze maybe? If so, squeeze the thing to get pressure up then go for a start up.
If no priming system, have the performance of the in tank fuel pump checked, and also the rubber fuel pipes possibly letting air in.
A recent fuel filter is a good move too.
John :)
Thank you John

Recently I have changed the egr valve and put it through a full service.

I did notice that by the fuel injectors the fuel pipes 3 were relatively clean and one had more residue where the fuel pipe connects to the injector ( i have cleaned them all and will have another look after a bit of driving to see if it is a leak)

I think we are onto a winner with regards to fuel issue.

Other threads have mentioned build up in carbon so a carbon clean could sort it?

Cheers for any help though appreciate it
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The EGR shouldn't play any part in the start up - it should be closed anyway at this time.....this isn't to say it didn't need attention though! I wouldn't have any other 'carbon cleans'
just yet.
The injector operation can be checked by a diesel specialist, and they will see if the 'leak off' at the flexible pipes leading from each injector back to the pump are the same for each cylinder. To be honest I would have suspected some visible smoke here if there was an issue.
I guess the problems come once the car has been left overnight - and is pretty good for the rest of the day?
John :)
John again appreciate your time to reply back ..

It is such a weird occurrence if I leave it it seems to be better. Some times couple weeks go by and it starts fine. But I live and work 250 miles apart so if I drive back to work and stop at a services, or start/stop at a lights on way down then it starts doing it .. but not every time

When it does start having problems it will vibrate the car gradually and then quite violently untill cuts out then the next time I start (immediately after) it will have the problem for a short amount of time then just fire up.. It's good to go then

But I can't then let it stop or turn off as the problem comes back

As you can imagine at a busy roundabout on A5 it's quite embarrassing haha
It's a shame I can't share a video to this somehow cause that would better explain it..

If the car is doing this when it is hot, it puts a different perspective on things.....I'd suggest a lazy injector initially, maybe the injector itself or the wiring going to it.
When the thing is misfiring, is there any sign of the odd puff of smoke from the tail pipe?
John :)
Sounds like too much 'leak back' through the injectors to me. Remove the fuel filter, pour the contents back into the fuel tank, buy and fill it with injector cleaner. Start the engine and just run it for 30 seconds, idea is run it just long enough to get the cleaner drawn into the injectors. It then needs to be left to soak for as long as possible to work, at the very least over night.

If that helps, but doesn't cure it, you will need to do a leak back test. Every injector has a high pressure supply of fuel going into it and fuel it doesn't use, goes via a leak back pipe to be returned to the tank. If the injector becomes gummed up, it can leak to much back to the tank, which starves the engine of fuel. It is much more of a problem when trying to start the engine.

It can be proven, by spraying 'instant start' fluid into the air intake - if it starts then, almost certainly the problem is leak back. Another way is to measure and compare the leak back from each injector into glass jars.
Never noticed any signs of smoke.

But all this info Is much appreciated gents .. I'll be sure to take it all on board and try sort it
No mate .. Never had an issue with any smoke or excessive smoke being produced out back. Is there any way I can upload a small video file to this .. ?? I'm new to the forum world like

Cheers again boys
there should be a clear section of fuel delivery pipe on the low pressure side of the fuel system. Can you see any air bubbles in this section of fuel pipe when you finally get the engine started? having got it going make the engine speed increase and see if any bubbles appear in the flow of fuel, the odd small one isn't so bad but if you get a constant stream the you have air being drawn into the system, fuel filter of micro puncture of a fuel delivery pipe.
Is there any carbon build up around any of the injectors, like bbq residue, this could indicate leakage past the cylinder head to injector seals usually a copper washer down the hole this can give rough running and starting problems.
Can you get a reader on it which gives a real time reading of what the injectors are doing, through a laptop with the 'correct' software for the vehicle. This would give an indication or whether an injector is under performing
good luck

Done the leak back test and they all seem to be about equal. Injector 1 was slightly lower than the rest but not by loads so we all agreed the injectors seem already returning fuel. N03 though did have more residue around it again after I cleaned them all to see if any was leaking, and one guy thought it sounded different to the others.

Whilst running the engine for 5 mins with cover off did notice the engine runs fine and then every now and again skips or almost misses a beat ( imagine a heart that's got a murmur is the best way I can describe it).. this is why I thinks it's a fuel problem

One of them was asking about hot starts and cold starts and it seems that the issue occurs on hot starts. Which baffles people.

The vehicle mechs in my work all flocked to help and give input .. lost of contrasting inputs but one guy seemed to be the messiah .. he reckons the egr valve could be faulty or not installed properly. Could be stuck open ? So got it going back to same guy next Friday.

Anyone had any brainwaves, or epiphanies? Haha

Again any help is greatly appreciated..
Done the leak back test and they all seem to be about equal. Injector 1 was slightly lower than the rest but not by loads so we all agreed the injectors seem already returning fuel.

They should be leaking equally low amounts, rather than equally high.

It could be cam or crank sensor, which fails when hot, you could try finding them, so you can squirt them with freezer spray when it fails to hot start.

Not all do, but some cars flick their rev counter which proves the cam sensor. Cam sensor is needed for starting, but crank position sensor needed for running. Cam sensor will be near camshaft, crank sensor lower down near crankshaft.
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