Technical P0300 seicento

[fingers99]

I'd be inclined to pull the head (although you might like to see if you can borrow another compression tester in the meantime). Might be worthwhile doing a wet compression test while you're at it.

 

[seanhyde12]

Been fiddling with compression tester and now get readings of 1 63 psi 2 55 psi and nothing for others. I agree I'll try and borrow another compression tester. What's a wet compression test ?
I think it's looking like Head gasket again !!!!!! if compression tester is even vaguely correct.

 

[fingers99]

Another way would be to test the compression tester on another car.

Wet test, just pour 5ml (about a teaspoon, no more) of oil down each cylinder immediately before you test that cylinder.

 

[seanhyde12]

ok I've done a wet test 1 goes up to 80 2 gives 75 3 and 4 nothing. That must mean I have to remove Head to see what is happening. Do you agree ?

 

[seanhyde12]

JUst a thought . On an old aircooloed vw I had I once replaced cylinder Heads and after a year lost compression. I re torqued the head bolts and all was well. Any chance that could help here ?

 

[fingers99]

Nah. It's head off, check for flattness (etc) time.

I think the old VWs may have had copper head gaskets which would make it possible (if not best practice).

 

[seanhyde12]

Thanks for your time . so it's Head off again! I'll start now! and report back

 

[seanhyde12]

Right I'm back Head is off and on Bench. What am I looking for? It looks fine to me not like when I last did it and it was obvious where gasket had failed. As I removed Head gasket came off stuck to the Head. NOthing left on block. Tops of cylinders look same as when I did job before. Head on Bench I can see nothing obviously wrong with gasket which will come away from Head with gently prizing with fingers ?

 

[fingers99]

Or a decent solvent. You need to check the head for flatness with a straight edge or on a flat marble slab with feeler guages.

If the bores and rings look OK I'd be inclined simply to get it checked and skimmed.

 

[seanhyde12]

Cheers Fingers. I've just gone back and cleaned surface of Head and removed Gasket.Now it is clean I can see where the gasket has failed between 3 and 4 the two cylinders without compression.So problem solved.
This is the Head I brought off you a year or so ago. It looked great when you sold it to me and it still looks great now. I'm in a hurry to get the car going. Is it essential that I get it skimmed ? If it's now obvious what the problem is.

 

[cc1]

The block face will need checking for imperfections around where the fire rings of the head gasket are. I plug all the holes in the head with kitchen towel and use a large oilstone (one about 200x60 duel faced for sharpening chisels) and run it over the block. Rough side first, then fine side to finish. Vacuum all the muck up and clean with thinners. The head will only need skimming if there are imperfections anywhere that could cause a breach or the head is not flat. I would order some new dowels if any are rusty as they can get damaged on removal.
I would skim it to be safe and clean down with thinners. You also have to make shure the head bolts screw in with out resistance to achieve equal torque. Use an old bolt to clean the threads.
You need a calibrated low ranging torque wrench (needs to do 30Nm) to get the first stage correct and a dial gauge for the final stages. Use a quality head gasket, Payen/Febi/Fiat etc.

 

[seanhyde12]

Thanks Looks like skim will be the way to go . I 'll think about it over the rest of weekend. There does not seem to be any imperfections. The surface looks clean and flat. As I've done this before I guess this is a weak point on these engines . I think I've done about 20,000 miles max since I did the job last. On the positive side at least I can fix it myself. so thanks again for all the input

 

[cc1]

It's a weak point on any engine. When you build from new, everything is near perfect for assembly. A used engine requires more care.

 

[seanhyde12]

OK Head skimmed ,everything back together and running fine .However I'm now getting a P0351 ignition coil A primary secondary circuits code. As I've also fitted new HT leads and new coil packs .What could this be about? My only guess is a poor conection somewhere
Any clues?
Thanks
Just one thing. It does seem to run a tiny bit less smooth at idle than before. I'd put that down to needing a descent run giving ecu time to reset everything. I think I remember something about this.?

 

[fingers99]

Could well be that it just needs a run. Try gently scrapping all the coil connectors and coating with (wonder substance) silicone grease.

 

[seanhyde12]

Thanks. Taking for a good run this evening and will try the silicone grease. When you say coil connectors do you mean where the HT leads join or where the electric socket thing joins each coil pack or both?

 

[fingers99]

Both. Doesn't do any harm to clean the black bits of the coils with WD40 on a rag, either.

 

[seanhyde12]

Ok so I've sprayed some silicone onto connectors and will take for a run tonight again as engine code keeps coming up . Do you by any chance know which of the coil packs is ignition coil A primary secondary circuit, which is causing the code P0351 because clearly this code relates to one of the coil packs and not the other.
Thanks

 

[fingers99]

No. They may be designated A and B in the Technical Manual, but I'm not sure.

I would swap the coil packs round, see if the fauit changes.

If not, suspect the wiring to the coil (the low tension side).

I think -- "computer speak" aside, it should be ignition coil A primary (or) secondary circuit. Circuit being the operative word (my guess is that the coils and HT side are fine).

 

[seanhyde12]

Thanks Just to say I used the silicone spray ,fiddled with connections to coil packs and HT leads to coil packs. Result :so far no fault codes have shown for about 50 /60 miles. So fingers crossed job done.