Corsa won't start, low compression.

paddedjohn

Hi all, hope someone can help with this one. I've got a 1.2 sxi Corsa on an 04 plate, went to start it up and the engine just turns very fast but won't fire, I have put a compression test on it and I'm only getting 90, 120, 90, 95 out of it, the timing chain was done 6 months ago and the cams are turning and the valves appear to be opening and closing ok. In my head I've ruled out rings as the car hasn't been smoking and I thought maybe head gasket but no water in the oil and to get those low readings it would have to fail drastically in one hit. Have been told maybe the crank sensor but can't understand how this would affect compression, any thoughts please anyone.

maninthestreet

Are you getting a spark?

Foxy-Stoat_3

Only way to get low compression results are:

Bore wear (scratches etc)
Piston rings not sealing properly
Valves not sealing properly
Head gasket failure
Spark plug threads not sealing properly
Faulty compression tester/operator error !

Only way to be sure is doing a leak down test then a strip down.

You could put some oil in each cylinder and do another test again.

marlot

Those compressions look poor. To get them accurately you need the car at running temp, and throttle fully depressed while turning the engine over.

I agree with Foxy-Stoat - you need to do a leak-down test to be sure what's really going on.

Has the starting problem only just occurred? It might well be that the compressions have been poor for a while. Go back to basics first - do you have a spark? Are you getting fuel?

forgotmyname

Drop of oil down the bore to help seal them, Not too much though.

See if the compression increases. Did you do the test properly though?

vaio

engine turning unusually fast plus low compressions with no previous issues would get me thinking that timing chain has jumped a link and bent the inlet valves

Wig

Have you removed all the plugs for the compression test, and the fuel pump relay?

I work in bar and that's about 6 bar which is not good.

Put a teaspoon of motor oil in one of the worst cylinders and see if it improves the result.

Whilst you have all the plugs out fit them one by one to each holder on the coil pack thingy and check for spark at each plug holder.

So the engine was running the night before and now it isn't? Hmmm.

I would agree that turning very fast and low compression does imply that you have some serious air leaks in each cylinder, if it was a hole punched through the piston though you would get no compression at all, so it would indicate bent valves...........maybe if you take the rocker cover off, you can check the valve seals by pouring oil on them?

paddedjohn

Have tested the spark and thats ok and even tried a different coil pack. Years ago I was mechanic and mot tester so im not new to engines and if this was a 70's/80's/90's car i would be able to strip it down and rebuild it blindfolded, but these days there are more and more electrical aids and sensors than ever. With this in mind ive booked it into a recommended garage that has the proper diagnostic equipment to try and get it fixed. Thanks for all the replies folks.

paddedjohn

Update on this problem, I refitted the rocker cover and coil pack before Getting it ready to trailer the car to the garage, gave it one more try and after a struggle it fired up and is now running great. I've checked for any rattles and there are none and there are no codes showing when I plugged my reader in. Got to admit I'm totally baffled but at least it's running again. Car shopping this weekend methinks.

tedted

more than that the hyd lifters jacked up and when stood for a time slowly released there selves enough.

paddedjohn

How would the lifters jack up? Maybe 1 but not all surely