Is it possible to make fatal mistakes changing timing chain?

octet

What's all this stress about correct positioning before taking the chain away? i don't really understand why so much talk about the correct degrees of the cam sprockets and even a timing tool to setup the sprockets in place and hold them?

I don't have lot of experience with engines, but fitting the new chain with all the timing marks seems to be almost like a fool-proof job. Some great hero even counted the links between sprockets:
viewtopic.php?f=22&t=18394&p=1165781&hilit=6148#p1165781

As far as i understand the timing chain markings guarantee that the crankshaft and camshafts are synchronized. Is it possible that some other system gets out of the loop if the sprockets are not constantly held at correct position when chaning the chain? How is the ignition synchronized?

si_c1978

Re: Is it possible to make fatal mistakes changing timing ch

ignition is always synchronised by toothed wheel on the end of the crank(no second cam sensor), if the sprockets are not held in place the the engine will try to fire with the vavlves and pistons etc in the wrong place,
why spend ages lining up and shitting yourself when starting when you could have simply locked it all in position so that you dont have to????
obviously its a different kettle of fish if the chains slipped.

Gary14

Re: Is it possible to make fatal mistakes changing timing ch

And you would shit yourself if the pistons made love with the valves :o

Matt

Re: Is it possible to make fatal mistakes changing timing ch

Gary14 said:
And you would shit yourself if the pistons made love with the valves :o

:lol: :lol: :clap:

ATOM_X

Re: Is it possible to make fatal mistakes changing timing ch

I think I understand what the originator is eluding to

If the chain is aligned correctly there should be no problems
BUT
It IS quite a fiddly job to the unpractised masses hence the reason for ALL the help threads

If fitted incorrectly it may be fatal
BUT
if fitted correctly it may be a life saver

The moral is to check check & check again

astra22bertoneauto

Re: Is it possible to make fatal mistakes changing timing ch

octet said:
What's all this stress about correct positioning before taking the chain away? i don't really understand why so much talk about the correct degrees of the cam sprockets and even a timing tool to setup the sprockets in place and hold them?

First of its easy to move the cams to the correct position without the timing chain attached. Just make sure all four pistons are halfway up/down & your spark plugs removed.

octet said:
As far as i understand the timing chain markings guarantee that the crankshaft and camshafts are synchronized. Is it possible that some other system gets out of the loop if the sprockets are not constantly held at correct position when chaning the chain? How is the ignition synchronized?

FYes those marks are there to make sure you get it right. But the first time I changed a timing chain, i noticed that when fitting the tensioner the chain had a habit of slipping a notic or 2 on the bottom cog (crank) as it takes up the slack.

As AtomX pointed out check, check, check again & fit tensioner then quadruple check again! :thumbup:

octet

Re: Is it possible to make fatal mistakes changing timing ch

Well, i think i broke something as the car won't start. At first try there was some noise like trying to start but then nothing and i tried another time but didnt get anything out of it really. I didn't try very long though, just some more than it usually takes to start it up, as i want to be careful now not to do any damage in case something is going wrong.

I released tensioner before fitting and checked the timing marks after the fitting the tensioner. Also there was no strange sounds when turning the wheel after everything was in place.

One thing i noticed is that before i took the old chain off and was turning the wheel to get to this TDC position, there was some klapping noise when the engine hit this position. I might have turned the engine also backwards, i didn't pay attention to that, could it mess up something?

Now i took the top cover of and at least the chain is still there intact.
Edit: Also turned the wheel and there was no disturbing sound and everything was running smoothly (as far as i can tell). Also the number of links between intake and exhaust sprockets was correct (14). Maybe i'm just too careful about the first start..

ATOM_X

Re: Is it possible to make fatal mistakes changing timing ch

should start first time
Sounds like something is wrong

octet

Re: Is it possible to make fatal mistakes changing timing ch

I opened the bottom gasket and checked the timing by counting the links, it's correct. However, the car still won't start. The starter is doing it's job and turning the engine. I checked the plugs and they smell of fuel. As far as i can see from the plug holes, the pistons are dirty but i didn't see any broken pieces. Battery shows 12.75V. There are no dramatic noises from the engine when starting, only the starter.

Firstly i'm still concerned that i somehow messed up the timing, even though the marks on the chain are correctly aligned. Can this be the case? I did not use the timing tool and was maybe turning the engine backwards when setting the timing at first place before taking anything out. Only fatal mistake that i can think of, is if the crankshaft makes a full turn then the timing is out, or not? I think i turned it only a little, but am trying to consider everything anyway now.

Secondly, i'm suspecting the ignition since the plugs have fuel already. Is there some way to test the coil pack? Are there other systems involved that you could think of? The engine did fire once or a couple of times when i first started after changing the chain, but not after that.

Any help is appreciated

jwalker

Re: Is it possible to make fatal mistakes changing timing ch

check to see if you're getting compression, if so then check if you're getting a spark dunno..

octet

Re: Is it possible to make fatal mistakes changing timing ch

I took the coil pack with plugs out and at first didn't get any sparks. Then i noticed the power plug was badly connected and reconnected it and there were sparks! all four of them at the same time! (as i understand this also simplifies the timing between crank and cams very much). Then i put it back in the engine and got a different started noises. Every few cycles it now makes a different sound like maybe trying to fire but not quite. Could it be the plugs are too "wet" of fuel? I'll try again in the morning. How can i check the compression?

jwalker

Re: Is it possible to make fatal mistakes changing timing ch

you need a compression tester, were all the coloured chain links matching the marks on the sprockets when you fitted the chain?

octet

Re: Is it possible to make fatal mistakes changing timing ch

yep, as seen in example pictures in other threads, and now i counted the links it is correct. I can bet my drivers license on it, If i messed them up i'm propably not worthy to even own a car 😃

astra22bertoneauto

Re: Is it possible to make fatal mistakes changing timing ch

jwalker said:
you need a compression tester, were all the coloured chain links matching the marks on the sprockets when you fitted the chain?

a tester from halfords is about £30 but works a treat! I bought 1 when i done my timing chain.

octet

Re: Is it possible to make fatal mistakes changing timing ch

I was still trying to start it in the morning. I gave some extra throttle and it sounded more successful but still not starting. Then I gave full throttle but it started to make some dramatic popping sounds. Luckily it was not from the engine, but from the air box, which was trying to jump out of the car. I had attached it only loosely in place for this test so it could move a little. Then I removed the air intake pipe completely and finally with full throttle the engine came to live!

Acceleration is much smoother now so i guess the chain swap was successful after all. Only problem is a whistling sound with certain revolutions. I noticed the crank pulley is wobbling a little, and probably that's the cause. I guess i bent the screw when undoing it. I used a screwdriver from one on the holes of the pulley to the grooves of the engine to stop it form turning when loosening it. But it must have also been working as a wedge and twisting the pulley and screw.