Setting timing from scratch

[gbk71]

Hi all.

I've replaced my broken timing belt and need some advice on setting the timing. Engine is TU5JP4 1.6 16v.

I used 8mm bolts to lock the cam pulleys, put a screwdriver down cylinder No.1 (the one nearest the belt) and turned the crank until the piston was at the top. The groove in the crank pulley was then facing down. I fitted the belt with the 3 marks on the belt lining up with the timing marks on the cam and crank pulleys.

What I didn't do was lock the crank as I wasn't sure where the locking hole was. Down past the oil filter I think, but I couldn't find it. Does it matter? The crank just moves the pistons up and down, so as long as the piston of No.1 is at the top, then that's OK. Isn't it?

What concerns me is that the car doesn't start. Not overly surprising in itself, could be bent valves. But I expected some kind of spluttering at least, like it was trying. It turns over, but there's absolutely no life in it. So it's a spark/fuel/compression thing. Or timing.

Any ideas?

I did turn it over by hand a few revolutions and it seemed fine.

[mickthemaverick]

Hi and welcome.

You said you ensured no 1 was at TDC but was it at the end of its compression stroke ie valves closed, or at the end of the exhaust stroke with the exhaust closing and the inlet about to open? It must of course be on the ignition stroke when all the cam marks are lined up? Just a thought!

[gbk71]

Hi. Thanks for the reply.

I suspected there might be something along these lines going on. I've been doing some research and read about timing being 180 degrees out and that there's 2 revolutions of the crank to one of the cams. I can't get it quite sorted in my head though. Surely the crank just makes the pistons go up and down. From the crank's point of view whether it's on a compression or exhaust stroke is irrelevant. The relationship with the cams at a particular moment is what decides the type of stroke.

If I take the belt off and rotate the crank 360 degrees and put it back (the groove in the crank pulley facing down again) won't everything still be in the same position? Of course, if there's something else the crank does (injection pump?) then that's different. Maybe that's what I'm missing.

[mickthemaverick]

I see where you are thinking but if you consider that 1 revolution of the crankshaft turns the camshaft half a revolution you can see where it is possible to get the timing 180 out. However if the crank and cam shafts are set against their relevant TDC(Thanks Richard!) timing marks rather than relying on the screwdriver method, that will ensure that the belt is fitted correctly.

[RichardW]

Often the timing marks are not at TDC.... You really need to find the timing position of the crank and set it there. Have you had the head off? Seems unlikely it will have got away without bending some valves... does it sound like you are getting compression cycles?

[bobins]

I'd say either reset the crank after giving it a complete rotation, or do a compression test to check for compression / bent valves. Depends which way 'round you want to do it - crank timing first or compression test first.

[gbk71]

I'll have a look at it again tomorrow, weather permitting. Take the cover off and look at the valve positions. I agree it would be a miracle if there's nothing bent in there, but you never know. I'll get a compression tester and see. Thanks.

[wheeler]

From the crank's point of view whether it's on a compression or exhaust stroke is irrelevant. The relationship with the cams at a particular moment is what decides the type of stroke.

Yes, you are 100% correct.

As far as the TDC thing goes then on PSA engines (both petrol & diesel) not all of them line up like this, Many of them the timing is set up with all the pistons level halfway up the bores. I can't remember off hand if this engine is one of them. The only way to do it correctly is to peg the flywheel.

And yes i'd be amazed if there was no damage after a broken timing belt on this engine and if this is the case i wouldnt expect there to be even any kicking or spluttering like you were thinking.

P.S. Cylinder 1 on this engine is nearest the gearbox end.

[ozvtr]

This is a picture of a TU3 engine but the TU5 is much the same (as far as "pinning the flywheel" goes).

I use linch pins. The 6mm pin needs to be 30mm long in the inserted part. If you make it too short it wont engage in the flywheel. If you make it too long it will foul on the casting webbing when you try to insert it.