Hi,
I've been having a starting problem on my diesel Fiat Grande Punto 1.3 (08 reg, 64k) for a while now. I am not sure where the problem's roots lie, so will try to describe things in detail and hope for advice.

For some time after bying I started the car without waiting 10 sec for the glow plug light to go out. My mistake (first car; no diesel experience before). Corrected my mistake after some time, no warnings developed while I was starting incorrectly.

After some weeks the glow plug warning started flashing for about 15-20 sec after start, but starting was fine. Checked with a garage, they found code P0683 (pre-heat error) and said in most cases it's a harmless ECU error and I should not worry unless problems develop. Drove for 2 months with no problem.

Then starting became more difficult with colder weather: it took more time, there was more and more white smoke. Went to the garage again, they found same code P0683, and checked glow plugs. One plug was shorting internally and causing controller to overload and cut-out. When replacing the plug, one was snapped; one seized but working; two were replaced for new ones. I needed the car urgently so had to collect it from there.

Drove a couple of weeks on 3 plugs (2 new, one old). The car started great, but warning light continued. Same code (P0683).

I wanted to see the problem to the end, so a specialised engineer drilled out the broken plug and the seized one without removing the head; and put 2 new plugs in. All plugs have now been changed. All plugs checked for current and seem to be working correctly.

However, the problem with starting is back: it takes 10-15 sec of spinning to start (sometimes takes 2 attemts), and there is a cloud of white smoke when it finally fires off. Same warning flashes for about 20-30 sec after starting (P0683). Once or twice it started without smoke or spinning, but that is very rare. Once started, the car runs beautifully, no alien sound, full engine power.

Any ideas or advice?

My questions are along these lines:
1. I am surprised that before drilling the car started way better on three plugs than now on all four. Could this outcome be caused by some mistake in the drilling, say cylinders got affected? Or in that case symptoms would be more severe (loss of power, alien sound, etc.) Should I take it as a coincidence with some other problem getting worse?

2. If it's not the glow plugs, what could it be? Electrical? GPCM? The flashing glow plug light leads me to suspect something is still wrong there... What should I get checked next?

3. Could this somehow be a consequence of me starting the car in a wrong way in my first month after bying? What are the possible problems caused by such a start?

4. Could it be a problem with the battery in some way? Say, it gives weak charge to glow plugs? I had a battery go flat once when I was away for 6 weeks and had to jump start it. But I am driving actively these days, and the starting problem is there.

Would appreciate any advice!