Bought an Audi A4 as spares or repair off ebay, cambelt snapped at lights apparently. Heads been off and the following work has been done;

The car will not start, there is very very low compression in all 4 cylinders, won't start off a bump start or nothing, fuel is getting up and there is a spark and timing is correct according to Autodata.

Its a 2.0 Petrol ATL

 

Has the head been pressure tested?

 

Yeah, done a leak test on the pistons too

 

Have you done the work on the car, or have you been told that's what's been done?

 

All of the work was done here in the garage, apart from the head works, but that was sent off to someone who we've used for years and never had a problem with, they even sent someone out to see if he could solve the problem, he suggested the leak test which proved nothing.

 

Have the lifters had time to pump back up?

Try taking the plugs out and spinning it over for a while, see if the compression improves then.

 

Is it a non interference engine? If not then i would have expected at least one bent valve, sounds like you have at least one in every cylinder. Have they timed it 180 degrees out?

 

have you fitted the correct head gasket? silly i know but possible.....

 

He said the valves were checked and seated though?

Mind you, might not have been done properly, lol

 

Thats what i was thinking

Didnt realise you were back chip, welcome back, right where you belong

 

All the valves were taken out, inspected then lapped in so none are bent

 

i would have said lifters. plugs out and good old turn over.then compression test

 

Check the Cam pulley is on the correct way round. IIRC they can be put on either way round and have 2 very different timing marks on each side. Hope this helps.

 

Surely this would mean the valves are closed longer than they should be, so pumping them up won't increase compression? Decrease it if anything...

 

lifters cause the valves to stay open

 

I would say you have bent valves, despite being ok when fitted, was it definitly times up correctly, else this could have bent them since?

As said lifters open the valves, so if they were suspect you would have the complete opposite effect, i.e. high compression, in any case I can't see it would stop the valves opening.

Martin

 

take the cam/followers out (whatever is easyest) then compression test, easy.

 

That will bend the valves.

edit - no it won't!

 

If they have no oil in them, they will be short, and the valve will stay closed. Surely?

 

if the lifters are taken out the valves will be closed.

 

I may be inclined to check the oil pressure at the cylinder head. I have heard the head gasket can go the wrong way round and stop oil getting to the head.

 

they get pumped, locked, extended too far when removed if they dont get all the oil squeezed out before refitting, very bad practice to fit without doing this IMO because this happens!

"That will bend the valves."
how? seriousley..... how?

cams and or lifters out, belt off, ALL valves are 100% closed under spring pressure and if seated properly will have compression, if not head back off.

 

What? Taking the followers out? Don't be silly *



* unless this engine is built very different to everything else...

 

if the valves can not opened there will be no air to compress to get a compression reading. If the readings are low to start with I would look at top end oil pressure to see if the lifters are getting the oil they need.

 

Cant compression test it with the cams out, it wont be able to breathe any air in.

You can only leakdown test it like that.

 

see your point

im aproaching this differently due to it having a lot of work and possible hidden faults from last owner/destroyer

interesting one.

 

the only thing that I can think of relates to lifter ,when I done the v8 I got a new lifter set and even though this was a new build engine and I drill primed the oil system it was a long lead time before it would run.

 

I had the exact same issue when rebuilding my brothers 1.8T A4. I timed the head sprocket and crank perfectly and turned her over by hand to get the oil into the cam followers, however I wasnt aware that there are actually timing marks stamped on the rear of each cam which need to also line up. As a result I bent all 8 exhaust valves. My guess you've done the same. See link below to a thread that will show you the rear cam timing marks. Its very easy to miss as most cars time on just the front cam and crank.

http://www.passatworld.com/forums/61...tensioner.html

See below link also to a video of my brothers car turning over.....at the time I couldnt work it out so removed the head and discovered all 8 exhaust valves were bent....gutted as I had just replaced them all!

If your engine sounds the same on turn over the exhaust valves are bent mate sorry.

http://s182.photobucket.com/albums/x...10205-1132.mp4

 

Would this be them?

 

Hey yes thats my bro's valves......and the wifes kithen table cloth!

 

Oh yeah, I'm a daft cunt.

But as Chip says if valves are closed then the engine cannot inhale/exhale thus no compression.

Leak down test will prove if bent valves or blow by on the pistons of course.

 

ill try all the things suggested when i can quite busy in the garage tomorrow i think, pretty sure we got the back little arrow timing marks on the cams though as we used Autodata to confirm the timing first. I'll ask the boss though as it was him who done it first time round.

Quite worried about that video though, sounds the same, but there is a slight popping noise as if its firing, but its not a big enough bang to kick it into life, which is what low compression would explain. Really hope the valves haven't had a fight with the pistons though, its a 20 valver

Edit to add;
To do a leak down test i remove the belt and cams, what about spark plugs, what shall i replace them with?

 

How about the leakdown test tool ?

 

Rightio!

 

Spooky, Eh?

Good link for the cam chain change.
Might be usefull in the future, as I've just bought a high mileage 1.8T Skoda, runs O.K now I've replaced the blocked oil pickup tube (common problem).