Periodic start problem, leaving ignition on for minutes helps...

[johnjorgensen]

Hi all. I´m in Denmark, (the danish VAGforum cant help, so here goes). Car is a 2004 1,2l 12valve. Engine AZQ.
210.000km on clock
Timing chain changed by me at 207.000 Car runs nicely once started.
Problem is car starts always, but really bad. Bad as in 10 or 20 tries. Leaving ignition on for a minute or 2 seems to help. Happens typically after a days still stand, but not always. Mostly cold starts a problem. Sometimes the problem is gone for 10 starts, then returns.

Bought a V-checker V303.
Usually no error codes despite start problem.
The other day it said Error 0303 ignition failure on cyl 1 and 3

I reset the error. Car started. Next day difficult start and no error.

Ignition coils, sparkplugs, alternator, map sensor, battery, injection changed or checked.

Where do I go from here?
Any advice apprciated, regards John

[Rob69]

maybe fuel pump problem - can you check fuel pressure at injector header, might also be worth checking compression as that's pretty good distance on one of those engines, I'm thinking exhaust valves maybe worn.

[johnjorgensen]

Thanks Rob. I already tested petrol pressure. It was fine, and after checking, the damn car startet like a dream. For a day or so, then back! Ill look at compression...

[johnjorgensen]

And then again, could it be that I have a petrol pump that works on-off. I can hear it start every time I open the door...

[Rob69]

That may be a clue to the fault then, especially if you have to leave the ignition on for a while to help it start, maybe the pump is working intermittently or struggling to achieve pressure? there is a pressure regulating valve somewhere in the system as well. If it was compression related it might be a bad starter every time rather than intermittently.
to
Thanks Rob. I already tested petrol pressure. It was fine, and after checking, the damn car startet like a dream. For a day or so, then back! Ill look at compression...

[johnjorgensen]

I measured the pressure 4 times over a couple of days. Went straight up to 3 bar. So an error in the petrol pump, that come and go? Sounds like a plan to check it.

[johnjorgensen]

Weird car. Changed the petrol pump unit in tank. And camshaft position sensor. (Tried to run car without camshaft sensor, it ran normally, indicating that crankshaft sensor is ok too). No difference when we talk starting: Often bad cold starting, best with ignition on for a minute or so. Once started it runs sweet. Engine lamp went on and then off again. OBD reading said ignition problem cyl 1 even though lamp was off again. Ignition coils? (already changed but not for new ones) I measured ohms on both sets of ignition coils, 5 was similar, 1 was way off.

How do I properly measure ignition coils?
What readings should I expect from lambda 1 and 2, hot or cold?
Thanks for your ideas ;-)

[johnjorgensen]

Replaced the coils with new Hella stuff. Not better. Do these cars have an issue with broken cables? Like Ibiza mk4? Could this be the problem? Where do I start??