Technical VVT Cam Sprocket Help Required

[cskerry87]

Afternoon all. I'm new to the forum and hoping for a bit of expertise if anyone would be so kind. Please forgive me for any etiquette mistakes, and I'll try to keep this as concise as possible while providing some background:

Last week I changed the timing belt and water pump on my wife's 500 (2012, 1.2 8v, Euro 5 engine). I followed a combination of Youtube and Haynes manual, and have changed cambelts successfully on my own cars in the past.

I completed the job using DIY timing marks on the sprockets and block (gold sharpie works a treat, by the way) and did not lock the crank or cam shafts. At the time, I didn't notice the advice in the Haynes manual to slacken the cam sprocket before tensioning the timing belt, so the sprocket stayed undisturbed and I finished the job. I rotated the engine by hand 2, 4, 6 and 8 times, and my marks realigned perfectly.

The engine started and idled fine, but when I ran the engine up past 3,000 rpm I got a shuddering misfire and a flashing engine management light. My little OBD reader flagged up "multiple misfire, cylinders 2 & 3". The funny thing was that as soon as the ignition was switched off and the engine restarted instantly, the idle once again ran fine and the EML had disappeared.
These symptoms repeated almost every time I ran the engine revs up beyond 3,000.

So, I thought since I hadn't used the locking tools when changing the belt, I had better order the tools, strip everything down and check the timing. I did so, and the timing tools fit on together with the belt in place, suggesting the timing is spot on. Hmm.

The only other thing I hadn't done originally was to slacken the cam sprocket before tensioning the new belt, so I thought I should do so now to eliminate that, before looking into coincidental problems with plugs/coil etc.

Here comes the cock-up...

My engine is a Euro 5, which has what I now know to be the VVT cam sprocket with the brass-coloured cover. Unfortunately the Haynes manual mentions nothing about the VVT mechanism, and only says that on Euro 5 models the sprocket retaining nut cover needs removing.

I struggled to slacken the central torx nut, so very stupidly decided to remove the small torx bolts around the edge of the cover. When the last one was out, of course the cover sprung off and dropped a load of oil, and the internal spring released its tension (albeit the spring is still in place). I then notice the small text on the cover: "do not remove cover" :bang:

If you're still with me I thank you for your patience! The upshot is a few questions:

1. Is it possible to reattach the cover to the VVT pulley, or am I screwed and will need to buy a replacement pulley?

2. If I do need to replace the pulley, does anyone have any advice on the fitment process? Is it as simple as removing the central torx bolt, sliding the old pulley off, sliding the new one on and torqueing the bolt up? Or does the new pulley need "setting" in a particular position somehow?

3. Is it actually important to slacken the cam pulley before tensioning the new timing belt, or was I just on a wild goose chase in that regard? My timing marks lined up perfectly following tensioning, and obviously the timing tools confirmed that the shafts were in the correct phase relationship, so should I have just left the pulley alone? And if I fit a new pulley, should I leave it slack until the belt is tensioned?

4. If I get the pulley issue sorted and the belt back on and am happy with the timing, does anyone have any ideas to explain the misfire? Surely it's too much of a coincidence to have a faulty coil pack or plugs immediately after the belt change?


Sincere thanks for reading if you've got this far!

Stay Safe

Chris

 

[chris3234]

The misfire light above 3k rpm. Is a surefire sign the car needs a phonic wheel relearn

 

[cskerry87]

Cheers Chris. Is the phonic wheel relearn something that can be done DIY, or will it need to go into a dealer?

 

[varesecrazy]

Cheers Chris. Is the phonic wheel relearn something that can be done DIY, or will it need to go into a dealer?

It needs software..

MultiECUScan is very popular on the forum..

There is even an MES register of members with the kit who are prepared to help others

 

[jackwhoo]

2. If I do need to replace the pulley, does anyone have any advice on the fitment process? Is it as simple as removing the central torx bolt, sliding the old pulley off, sliding the new one on and torqueing the bolt up? Or does the new pulley need "setting" in a particular position somehow?

use your new special tools to set position of crank and cam shafts prior to fitting belt and cam sprocket (in any orientation as it is not keyed to camshaft in any way)
Tension belt, then tighten cam sprocket bolt while counter holding the cam shaft with a spanner , I don't think the cam special tool is meant to hold camshaft while torque setting cam sprocket bolt.


3. Is it actually important to slacken the cam pulley before tensioning the new timing belt, or was I just on a wild goose chase in that regard? My timing marks lined up perfectly following tensioning, and obviously the timing tools confirmed that the shafts were in the correct phase relationship, so should I have just left the pulley alone?

I think you were unlucky.

Good luck

 

[jackwhoo]

completed the job using DIY timing marks on the sprockets and block (gold sharpie works a treat, by the way) and did not lock the crank or cam shafts. At the time, I didn't notice the advice in the Haynes manual to slacken the cam sprocket before tensioning the timing belt, so the sprocket stayed undisturbed and I finished the job. I rotated the engine by hand 2, 4, 6 and 8 times, and my marks realigned perfectly.

If you had loosened the cam sprocket bolt without using the special tools it is possible on turning engine over piston would have hit valves because cam sprocket is not keyed to the cam shaft.

 

[cskerry87]

Thanks Jack.

 

[Pugglt Auld Jock]

There's been a very recent thread which covers a lot of this in the 500 section. it's headed "Cambelt change - Lost the position of the gears".

Whether you can reassemble the pulley successfully or not I don't know but it's subject to full engine oil pressure at certain times. So, in the words of "Dirty Harry", Are you feeling lucky punk?

The VVT pulley (and some earlier solid pulleys - for instance my 2010 Dynamic Eco 1.2 8 valve Panda for one) is not keyed to the camshaft (the crankshaft pulley is) so if, for any reason, you slacken off it's main retaining bolt (that's the big one underneath the screwed in plug in the middle of the pulley - you can't see it until this plug is unscrewed, watch out for a bit of oil leaking when you do) Having slackened it you will only be able to get the timing correct with the timing tools. Here's what the kit looks like: https://www.ebay.co.uk/itm/Engine-T...872744?hash=item23cef2c7e8:g:JLUAAOSw4TVeHWiW

Don't try to use the cam locking tool which fits into the slot at the back end of the cam to stop it rotating when undoing or tightening up the pulley retaining bolt. This bolt is EXTREMELY tight and you'll snap off part of the end of the cam where the slot is. If you look at the kit shown in the link above there is a wee black "blocky thing" in the middle. It's the one with a silvery coloured Allen screw. This screws into the front of the head and engages with the pulley to stop it rotating - you might find you will want to clamp a mole grip (other brands are available) to the camshaft for additional leverage to stop it rotating.

There are posts on here about how hard it is to slacken this pulley bolt because it's so tight and then to re-tighten it satisfactorily. Actually it's very doable if, like me, you have a comprehensive tool kit and considerable experience. Rather different if you're just a DIY bloke working at the kerbside with a limited choice of tools.

I'm a great believer in letting "sleeping dogs" lie so when I did the belts - and water pumps - on both my own Panda and my boy's Punto 1.4 8valve which has the VVT pulley, I first read Andy Monty's guide in the grande punto section and then set out to experiment as to whether it can be done without slackening this pulley. If you want to read about it type in "Becky's Timing Belt" in the search box at the top of the page and look for "Becky's timing belt - the ongoing saga". I put down my findings there for all to read.

Hope this is useful. You need to get your hands on a set of the timing tools and someone with Multiecuscan (MES for short): https://www.gendan.co.uk/product_FESPKG.html to do a Phonic wheel relearn - this teaches the ECU the new relative position between the signals being emitted by the crank and cam sensors after the new belt is fitted.

Care to tell us where you live? Not actual address of course. because some of us, for various reasons, prefer not to admit to having MES and offering it for general access. I'm one. So maybe there would be someone near you who could help with MES or maybe the timing tools, if we knew roughly where you are.

All the best
Jock

 

[Pugglt Auld Jock]

At the risk of depressing you here are a few direct answers to your original questions:

1) I don't know, never tried.

2) Replacing the pulley is really quite simple. Unscrew the plug in the middle of the pulley. Lock up the cam - but not with the tool which engages the slot in the end of the cam. Then, probably using your longest and strongest power bar, undo the retaining bolt and slide the pulley off the end of the cam. It's not keyed. It drives purely because that bolt is so darned tight! Note: The Fiat main dealer and my wee local Fiat specialist both told me the bolt is good to be used a number of times as long as it looks to be in good order.

3) If this was the first belt change since the car was built then the cam pulley would be as fitted at the factory so probably you would have been absolutely fine to just have left it alone. The problem around this pulley arises when you can't be sure whether it was timed up correctly by someone in the past. So, unless you can be sure that it hasn't been "got at" in the past you are best to use a timing tool kit to check everything out. So, in the position you now find yourself, you need to leave the pulley retaining bolt slack (half a turn slack is plenty - it just needs to be slack enough for the pulley to be able to turn WITHOUT transmitting drive to the cam). The crank pulley will be locked by that "dumbbell" looking tool and the cam by the angular slotted bar. Then when you tighten the tensioner pulley the cam pulley will rotate slightly to it's correct position as the belt tightens and that's when you lock it up by tightening it's bolt (with wee black block fitted)

4) As Chris said, the missfire above 3,000 rpm is absolutely typical of needing a Phonic wheel relearn. Many people report missfire codes being posted following belt renewals and often following the job having been done by a "wee garage" without any Fiat experience. Many have wasted substantial amounts of money replacing coils, HT leads, sensors, etc, etc and still not managing to eradicate the codes being posted. Quite often the codes are posted but the driver reports no symptoms of missfire (ie, hesitation, jerking, etc). From what you are describing I doubt if you have anything wrong other than needing a Phonic Wheel relearn to be performed.

Think I've covered everything now? do just ask away if you can think of anything else.
Good luck
Jock
Ps. You say you've done belts before so I don't want to give any offence, but you must be very careful about turning the crankshaft now with the belt and/or top pulley not turning the camshaft. There has to be a very real risk a piston and valve will "get friendly" which could have catastrophic results

 

[Pugglt Auld Jock]

I should perhaps say that my reluctance to join the MES register is more to do with upsetting my neighbours - we are a quiet sleepy street - and the legal implications of working on someone's car which subsequently then goes on to develop a problem, perhaps an expensive problem! Nothing to do with a reluctance to engage with the good people on this forum!

 

[cskerry87]

Hi Jock, sincere thanks for your help.

I'm in West Yorkshire (near Leeds Bradford Airport).

In terms of timing tools, I already have the crank and camshaft setting tools, which I bought subsequent to the original belt change and have used to confirm the timing is correct.

I understand that I should not use the cam locking bar as a counter to my breaker bar when removing the cam pulley's bolt. Would you say that the special little black tool in the kit you linked is essential to secure the pulley while removing the bolt? I've seen elsewhere people using generic cam pulley holding tools, or even just a spanner on the camshaft.

I have a decent breaker bar which has never failed to release a tight bolt so far, so hopefully with an appropriate tool to hold the camshaft steady I should be able to get the bolt out. Does anyone happen to know the recommended torque setting for this bolt when I fit the new pulley?


Finally, if I can't find a charitable soul to help me do the phonic wheel relearn, what's my best bet? Take it to a Fiat specialist, or invest in the software and adapter myself? Is there a guide anywhere to the procedure within the software?

Thanks again

 

[Pugglt Auld Jock]

As far as slackening I think anything which stops the cam turning will work as long as it doesn't do any damage.

Tightening the bolt might be a bit more difficult without it? My Haynes manual gives the torque on the 1.2 engine in my Panda at 70nm. The 1.4 in my boy's Punto which looks identical, has a low initial setting (20nm if I remember and then tightening with a degree wheel after that) Although I like Haynes manuals and find them generally trustworthy I have occasionally found them to be incorrect so I always like to get info from 2 or 3 different sources (maybe the manual and the main dealer and an independent) before I proceed. I didn't slacken either of ours so I've not tested it in practice.

If you've read the bits I linked to Becky you'll know I didn't get any problems after fitting the new belt so didn't need to do a relearn on either vehicle - and both are still running absolutely fine. I'm now of the belief that if you don't slacken the cam pulley bolt the difference between an old belt which was in good condition - just old - and the new one is so infinitesimally small that the ECU doesn't pick up any angular difference between the cam and crank sensor positions so doesn't flag up that it thinks something is wrong. If you slacken the pulley bolt I believe there is bound to be a very small angular difference between how it related to the cam before and after it's re-tightened. The ECU notices this. Of course it doesn't know you've fitted a new belt and disturbed the relationship between the pulley and cam, all it knows is that the signal from the cam sensor is not now arriving at exactly the same angular displacement of the crankshaft as it was before. It tries to make some sense of this and it's nearest choice of possible causes is a missfire so that's the code it posts and because it's now managed to post a DTC it lights up the engine management light just to let you know how "clever" it is!

My guess would be that if, when you're finished, you manage to set the whole thing up so that there is almost no difference between the cam pulley position before and after then the ECU will be happy and the engine light will stay out. If you are lucky enough for this to happen you won't need a Phonic relearn. So, if it were me, I'd get the job done and take the car for a wee run making sure to take the revs over the 3,000 rpm a few times (don't know why but around 3,000 rpm seems to be where it all kicks off if it's going to). If the light doesn't come on - and you've got no actual missfire, which would of course point to another problem all together - you're home and dry. If it does you're going to need someone with a scanner that can do the relearn MES or Dealer tool. I think there may be others too but you're not going to do it with a cheap generic code reader.

If you're going to do your own services and repairs long term on the vehicle it's a no brainer to buy your own licensed copy of MES. You can download the software for free at: https://www.multiecuscan.net/ and run it in simulate mode to see what you can do with it. Then buy the interconnects etc if you decide to use it on the car. You will need it to reset service warnings anyway which can't be reset without it - no pushing dashboard buttons etc will do this. I strongly recommend contacting Gendan and have a chat about it. I deal with a chap called Grant who is very patient and extraordinarily helpful. If you buy from them they will give ongoing free advice and help virtually for ever. By the way I have no interest in them apart from being a very pleased and happy customer. MES is also the tool of choice for many on here and there is, as a result, a wealth of knowledge on how to use it, you just have to ask.

 

[Pugglt Auld Jock]

Oh. I should have said, there are extensive helps and diagnostic interpretations included within the software which appear as needed. It's a very easy and powerful bit of kit to use. You do need to follow the instructions carefully when aligning the software to the interfaces. Not difficult but you don't want to rush it. Follow the instructions to the letter. I didn't, rushed in without reading all the instructions and ended up spending a couple of hours backtracking to find the silly mistake I'd made!

 

[cskerry87]

Cheers again Jock, thanks for your input.

Just to clarify - I didn't just get the EML, the engine was shuddering quite violently as soon as the light came on. So it doesn't seem like a "phantom" misfire, more like it actually starts misfiring. As soon as you cut the engine and restart it, the problem goes away until you increase the revs again. Does this not sound like the phonic wheel issue?

I'll see what happens when I put it all back together and go from there. Looks like I'm dropping £130 on the new pulley... and this job was meant to save us money! :doh::doh::doh:

 

[cskerry87]

Just to add for further clarification - I didn't slacken the cam pulley at all for the original belt change, so does that further suggest that it isn't the phonic wheel issue? Surely if the pulley hasn't been slackened and just the belt swapped, how would the ECU detect anything had changed? Cheers

 

[Pugglt Auld Jock]

Hmmm, you have a good point there. Does sound as if something else is going on too doesn't it. The Phonic wheel "thing" - which I haven't experienced at first hand by the way - seems to give you the light but not so much the physical symptoms of a missfire although I've read of instances where performance was "reduced", whatever that means.

I think you just have to go on with doing the job "as per the book" using the timing tools so you know the setup is correct. If you then still have problems I'd probably start with a compression check just to be sure a valve hasn't been damaged during all these "shenanigans". I'm a very "hands on" person and from my point of view trying to advise, with more complicated problems like this, I find quite difficult.

Please don't beat yourself up too much over the pulley (a bit of stress relieving swearing is permitted). I'm supposed to be a City and Guilds qualified mechanic and I've done plenty of "silly" things in my time. Have you tried Shop4parts for the pulley? They are not always the very cheapest (sometimes they are though) but I find their quality of parts is really excellent. (much of which they import direct from Italy I understand) They are also very helpful and pleasant people to ring if you're not sure about a part (don't get confused, they seem to have multiple Mike/Micks). They are my automatic first default supplier.

I had one last thought about the MES. If you decide to buy the interface connectors I've seen quite a few posts on our Forum from people who have bought cheap interfaces on ebay - and there seem to be quite a number of offerings - The problem seems to be that they often don't work properly. Some can, apparently, be made to work by opening them up and removing a resistor? I wouldn't be confident to do something like that. If you buy from Gendan, or another official supplier, you will probably pay a little more but it'll be a "plug and play" experience. My passion is for "messing about" with my cars, bike and horticultural machines, I want to be confident that something like this is going to work reliably and give results I can trust when I plug it in, not having to become an electronics engineer trouble shooting the diagnostic gear. I would encourage you to download the free software and run it in "simulate" mode where you can get quite a good idea of what it can do. You can even buy an interface and have limited (very limited) use of certain free functions without paying to licence it.

All best luck with it. Hope it all pans out well. do keep us updated on how things are going.
Kindest regards
Jock

 

[Pugglt Auld Jock]

PS. Just as a matter of interest, what make of belt did you buy? - I don't think it'll make any difference because these belts all, now a days, seem to be as good as the next one. I personally would opt for the Gates brand but that's just because we used to use them in the workshop and I've used them ever since and never had any problems at all with them so have confidence in them.

 

[cskerry87]

Cheers again Jock. It was a Dayco belt from GSF Car Parts. Seems decent enough quality to me.

I've ordered a new pulley for £96, so not too eye watering in the end. Just need to not tell the missus

I'm going to replace the pulley, re-fit the belt and make sure I'm happy with the timing, then go from there. I very much doubt I've damaged any valves because the cam & crank stayed in alignment throughout the belt change, despite not being locked. And when I cranked the engine by hand the timing was good, and there was no unexpected resistance when cranking.

I'll update when I've got it all back together, cheers again for your help.

 

[jackwhoo]

Cheers again Jock. It was a Dayco belt from GSF Car Parts. Seems decent enough quality to me.

I've ordered a new pulley for £96, so not too eye watering in the end. Just need to not tell the missus

I'm going to replace the pulley, re-fit the belt and make sure I'm happy with the timing, then go from there. I very much doubt I've damaged any valves because the cam & crank stayed in alignment throughout the belt change, despite not being locked. And when I cranked the engine by hand the timing was good, and there was no unexpected resistance when cranking.

I'll update when I've got it all back together, cheers again for your help.

Good move going for a new pulley, if you had got current pulley back together but it then sprayed oil all over your new belt it would be more drama.

Another good choice to get the special tools and go from there otherwise you could end up going in circles.

Dayco are a top brand along with gates.
Though I'm with jock if I'm looking for a belt kit and prices are similar I always go for gates.

 

[Pugglt Auld Jock]

Yup, I agree, fitting a Dayco wouldn't bother me at all - "The trade" use them a lot. As said above, I agree your choice to go with the new pulley was definitely the way to go. I too would have had to hide that purchase from my "Personal Financial Advisor/Keeper of the Family Purse" if I wanted to lead a peaceful life!

Also, from your description, sounds unlikely you've suffered any possibility of valve damage.

I'm going to follow this thread very closely for the near future because I'm absolutely consumed with curiosity to find out what your possible miss fire problem is!

Good luck
Jock