Over on Projects I'm doing a build which I've almost finished. I just got the timing belt on last night but it seems to be 'sticky' when turning over and at once point it just stops. I don't want to force it at all. I wound it back to the start position and it jumped a tooth on the crank sprocket. There are a number of reasons I can think of why it might do this:

• Harder to turn the four cams as well as the crank all on one belt?
• Pistons hitting the heads?
• 'Stiction' at the turnover point around TDC and BDC?
• Knackered tensioner

Help! I've already ordered another tensioner anyway, but any ideas will be appreciated.

 

have you tried a search mate? i seem to remember somone with a simular problem not long ago and it was solved.

 

I tried one but it didn't come up with anything. I must have tried the wrong search terms

 

If you think the engine is locking up -
Line the timing marks back up and drop the cam belt off again.
With the cam pulleys "off cam" - can you turn the cams by hand freely ??
If they turn ok,you know its not a tight cam cap.
With the cams in the "off cam position (all valves closed) - can you turn the crank ok or does it lock up in a certain place.

Mick

 

Right Mick, I'll get on it right now. Good thinking. Am I getting the timing belt on and off in the right place, i.e. lining it up on the four cam pulleys and fitting it over the crank sprocket and the tensioner last of all.

 

Some people have had the problem of oil squirters hitting the back of pistons?, i dont know if this applies to your block or pistons?

 

**** I hope not. I don't think that can be happening as it turned over pretty well without the heads on. IIRC...

OK I've just been and removed the timing belt. The four cams turn fine, smooth as silk off cam, ping off the cam when you push them a bit further. None have any particular sticking points that I could feel.

Then I put all four cams at rest and turned the crank. No problems at all, goes round and round perfectly smooth.

Soon as I put the belt back on, after maybe half a turn it just stops dead, same whether you go clockwise or anticlockwise. If you try to turn it any more it just tightens the already tight crank pulley bolt in, or jumps a tooth. I could see the tensioner pivoting upward just before it jumped, I'm sure. So there's got to be something holding things back.

Is it just me being a pansy and not wanting to force it round? Presumably turning four cams and a crank is going to be noticeably harder than each on one its own?

 

are the spark plugs in the head? could it be compression your feeling???

 

i'm just taking a guess but could the heads be on the wrong sides? would cause the timing to be out badly wouldn't it? i've never seen a head off the engine so not sure if they can be fitted wrongly.

but on some engines i've turned by hand i've came to points thats got sticky/hard to turn but i just put more pressure on it and it turned fine then would stick again. car started and run fine.

 

No, plugs are out, and the heads can't be fitted wrongly. Well I suppose maybe they could be, but it would be really obvious! THanks for the suggestions though. I wonder whether I should stick the crank pulley on as well and then tighten the bolt down into that so at least I won't worry about stripping the thread in the crank.

 

have the block or heads been skimmed and to much took out,

 

I just use an old hub nut instead of the pulley or a big washer so you can see whats happening.
does it feel like its hitting metal, can you tap against it as you rock it near the tight spot using a big bar but being gentle.
Mo.

 

just seen the picture on your project thread, turning the engine over like that will damage the thread on the bolt as you are in too far and the end is being squashed put in a washer or old hub nut then you will get correct torque but check the thread on the end of the bolt first.
mo.

 

They have been skimmed but CR is still right and there's a decent thickness of gasket in there. Without the belt everything works fine individually. I've fitted the old crank pulley on there and did that up, went for 120Nm for the time being. Turning on that, I can get the crank 3/4 of the way round i.e. from 12 o' clock to 9 o'clock then it stops. Whatever force it needs to get it further, it's more than 120Nm.

Bollocks. What can it be?

 

are you turning it the correct way when i did mine the manual said your only supposed to turn it one way.
Also if it turns over ok without the belt but wont turn over with the belt fitted are the correct cams in the correct places??

 

Well that's what I'm wondering. Each cam has a notch in it for the pin to go into as you tighten down the pulley. I wonder if one has gone wrong somehow? Or maybe I need different pulleys for STi3/4 cams?

 

Sounds like your valves could be coliding.

You did turn the cams opposite to each other on the left hand side when lining up the notches didn't you?

 

AFAIK, yes - the two-notch marks facing each other on the pulleys. The belt lines match up perfectly with the one-notch marks too. It does seem to me it's got to be something like that though. I just took the LH rocker cover off and there's a bit of Threebond that got onto one of the cam lobes, but even with that, the thing turns fine when its on its own without a belt. The tappets look like they're going up and down properly. I'm gonna think on this tonight. The only other thing I could think of was to do with the way the crank turns at a different speed from the cams, but I can't get my head round that. Surely if the crank sprocket line is at 12 oclock, that's right and there's nothing else to be done with it.

 

Certainly sounds like timing issue if everything is free before the belt is fitted. Have you got the arrow at 3 0 clock on the crank sprocket?

 

on the crank sprocket there are two marks. One is a notch the other is an arrow. Line the notch up with the mark on the oil pump.

Also make sure when you're lining the LH cam sprockets up rotate the inlet one clock wise to align it and rotate the exhaust one anti clockwise. This will ensure you don't get valve collision.

 

Maybe you have the exhaust and inlet cams in the worng place? ie exhaust cam in the inlet position on one side?

Just a thought.

 

Sounds like you've timed the engine up wrong somehow and the valves are hitting the pistons I can't think of any other explanation. Hope you havent damaged the belt with it jumping a tooth.

To add- Can you shine a light through the spark plug hole, you might see a mark which would confirm this? just an idea.

 

This is so weird. Everything checks out as far as I can see. The crank sprocket is spot on, notch at 12, triangle at 3. The belt lines up perfect with the crank sprocket and the four cam pulleys. Independently without the belt everything moves fine. I've taken one rocker cover off and I'm about to remove the other.

I have noticed some Threebond has got into one of the LH cam journals, I wonder if this is compressing once the belt tension is on and just totally jamming it up at a certain point? I'll clean that out and try again.

 

did someone not have to cut some of the skirt away on the pistons to clear something ?

vague recollection....

 

Oil squirters iirc...

 

What cam pullies do you have on there? and what cams?

As stated above, you definitley have the inlet and exhaust cams the right way round?

 

Having briefly read your project thread and here, am i right in thinking you can only manage 3/4 rotation clockwise?

Is this with the tensioner deployed or still pinned closed?

When putting the timing belt on i have always done the following sequence

Crank
Tensioner
Inlet cam of 2 and 4 (no slack between here and crank)
Exhaust cam of 2 and 4 (no slack between here and inlet cam)
Water pump
Toothed idler
Upper idler to left of Crank
Inlet cam of 1 and 3 (no slack between here and crank)
Exhaust cam of 1 and 3 (no slack to Inlet Cam)
Lower idler to left of Crank
Remove pin from tensioner

This ensures that no extra teeth arrive between inlet and exhaust cams of each bank.

When it is locking up, have you looked down the inlet and exhaust ports to see whats happening with the valves (look at them before it locks up too)

Just thoughts

 

Inlet Cam is longer so cannot fit in exhaust position.
Cams can be wrongly fitted left to right - will time up and rotate but engine will never fire up.

 

on some engines cams are same length ,we had car towed in (after rebuild some where else) with this very fault. left head(pass side) cams in wrong way round.

 

Thanks for all the ideas, keep them coming. The cams are definitely right. L4EX and L4IN on the LH (2/4) head and when I get the rocker cover off the other side, I hope to see R4IN and R4EX on there. I suppose there's the possibility I might have put the RH in and ex cams in the wrong way round?

They are WRX 4 pulleys and heads with STi 4 cams and valvetrain.