The rear bank is "1-2-3" looking at the engine, left to right... i.e. cylinder 1 is at the end nearest the cam-belt.


Ralf S.

 

If you look on the coil, you will see little numbers by each HT port that tell you which cylinder it expects to be connected to.


Ralf S.

 

Brilliant RalphS, exactly what I needed to know.

I must be going blind as well as daft. It's such an important thing to get them right I felt sure there ought to be an easy way of doing it, and there was

A short thread this time!

 

I just went out and scraped half a ton of snow off the beast, and took a picture of the coil and plug lead layout, so I could look at it back in the warm! I had got it right after all...

Sure 'nuff the little red studs next to the leads have a pot number on, and now I see the blown-up pics, even the plug leads have the numbers printed along their length - no expense spared, just one of Alfa's unexpected little surprises. A lot of people would fail to notice that in the entire life of a car.... like I was going to until today.

 

It goes cylinder 1 - 2 - 3 - 4 - 5 - 6 clockwise starting from the rear bank timing end cylinder.

You've also found why a lot of V6 155s had misfire probems, folk fiting the leads wrongly, haha.

 

Thanks Smaky, but that would mean the front set of cylinders (L to R looking in from the front) are 6-5-4, and the markings on the cam cover are clearly 4-5-6, so clockwise doesn't quite cut it???

You and Ralph both agree on the back set tho, and that was what I wanted to know - thanks both

Even a misfire would be nice at this stage of the problem!

 

Aye! I was impressed when I noticed it.. the cylinders, coil and the leads are all numbered-up by the factory. :thumbs:

It does come in handy from time to time..


Ralf S.

 

Further to all that lot, does anyone know, just to complete the picture, if cylinder 1 compresses and fires at TDC indicated by the flywheel "missing teeth", or where if not.

 

I think it's at TDC when the flywheel mark likes up with the arrow at about 11 o'clock to it.

From memory the mark is about 120 degrees anti-clockwise from the missing tooth.. but don't quote me.

Ralf S.

 

Trigger gap centre is 90 degrees BTDC on all the Alfa V6 motors I've played with so far.

Also, the cylinder numbers are cast into the cam covers. Can't easily see the ones under the plenum of course, but the front bank are easy enough to see. The firing sequecne 'ripples' along the engine from one bank to the other, starts at #1 then works towards the flywheel end. Visualising this can help to make sure you put the leads back right

 

Thanks Chris, but now I am getting a bit confused...

Clear about the TDC position, thanks, but when you say "starts at 1 and ripples towards the flywheel end", does that mean L to R as you look in from the front, or am I confusing the toothed timing wheel (L) with the real flywheel at the other end, connected to the clutch etc?
(I think I've been mistakenly referring to that wheel as the "flywheel" and the timing sensor as the "flywheel sensor" without thinking too clearly.) Silly me:cheese:

I'm beginning to think I might have a valve timing problem anyway, as one of the cylinders tested so far (5) is showing no compression, which could be for a number of reasons, all pretty dire, including bent/stuck valves and broken conrods....(although I imagine that would be quite noisy, and it wasn't). I will take the cam cover and cambelt cover off soon to investigate. Tension is OK, but a few missing segments on the cambelt could explain everything - is this what happens when they get old and tired?

I'm thinking of making a gadget with a TV camera and a small mirror and light source to drop into the cylinder via the spark- plughole for a good look around. If it's successful it might even be worth marketing, and a lot cheaper than the medical variety!! Or maybe a career videoing the insides of peoples engines - riveting viewing for when the in-laws come to tea

 

The small pulley at the water-pump end with the triger on is normally called the crankshaft pulley (or damper sometimes), the big lump with the clutch bolted to it is called the flywheel, as that is it's function.

Some engines (Ford Zetec from the Mondeo for example) have holes drilled in the flywheel for triggering.

Ah, think you may have found the problem. If you have got missing teeth on the cambelt then you have a fundamental and probably expensive problem to resolve I'm afraid.

I know (don't ask!) that one of these will run tolerably well with 1 cam 1 tooth out. I also know that they run with the crank 1 tooth out (which is more surprising). Any more and you are likely to end up with metal to metal contact.

If the belt has got to the stage of shedding teeth, it's either been badly contaminated with oil for quite some time or it is way, way past it's scheduled replacement interval.

Good luck with the endoscope/camera idea. Let us know how you get on. I've seen commercial endoscope kits for around the £200 mark but no idea how good or bad they are.

TBH, if it turns over, even with 1 cam way out, I'd expect it to at least try to start if you have air, fuel and sparks.

How about this; remove the AFM, crank it over while squirting some lighter gas at the throttle plate. Should be enough for it to fire and maybe run briefly if everything mechanical is in place.

BTW....what compression figures did you get for the cylinders that did make the needle move?? Assume you did this with the throttle wide open, yes? (forgive the basic question, but it's always wise to ask).

It's intrigueing and no mistake.

 

Thanks for all the comments Chris.

I've not got around to looking at the belt yet, and the compression test was more of a try-out of the instrument - no quantitative results yet, and I have to take out the three rear plugs to try them as well.

Is it just me or is it a really messy job getting 1-2-3 out? Needing removal of other bits and pipes particularly for 2 and 3, even with a long and articulated socket drive.

I didn't have the throttle wide open but I will do next time. No reason yet other than horrific imagination (and guilt) for suspecting the cam belt, as I suppose I've looked at just about everything else and it all seems relatively OK. (Including going inside the ECU, buts it's allowed because it's the sort of thing I do in real life!!)

 

Ah, OK, you're just paranoid like me then

The electronics on these things are usually very reliable. The electrics like relays and wiring, less so. Sensors are also prone to failure, but if you've got a good cranking signal (which it seems you have), sparks, which it seems you have, and fuel, again you seem to have that...it relly should make some effort to go. Engine water temperature sensor is important to good running, but it should at least start even if that's gone totally OC. AFM again is improtant to good running, but it'll go without one. Throttle pot - yet again...it should idle more or less. You've probably eliminated all these anyway since you don't have any stored error codes.

Having spent a considerable time going round and round blaming all manner of unlikely things in the past myself, I find it pays to step back, and start again from the beginning. Assume nothing, especially if it's something simple you already tested! (ask me how I know....)

Crank trigger - check. Confirmation of this is that the pump continues to run as you crank the engine.

Fuel pump - check (we think). Slightly awkward to test for sure, but you can test the entire fuel system more or less by taking the return line off the pressure regulator and feeding it to a container of some sort. Crank the motor - if you get a steady stream of fuel, then you know the pump and lines & filter are OK.

Fuel pressure. If the above OK, you really need to get a gauge and measure the line pressure. Simple enough to 'T' it in to the high pressure side. Doesn't matter where really, anywhere between the feed line from the pump and the pressure reg is fine. I usually use the feed end of the rail myself. You should see around 3 bar at cranking. At normal idle, you'll get roughtly 2.5 bar, but really, it's not that critical at this stage as long as the numbers are there or there abouts.

Sparks - check we think. A confirmation of timing and spark presence would be a simple old fashioned timing light. Connect to #1 and aim it at the timing mark either on the crank pulley, or if you can get to it, the mark on the flywheel that should be visible through the hole in the top of the bell housing. Expect something like 10 degrees BTDC or so I'd guess.

Compression check - remove one plug at a time, do each cylinder in turn with the throttle wide open. Just unplug the ECU or remove the ECU power relay when you do this just in case(!) it tried to start. Depending on the condition of the engine, you'd want to see at the very least 150psi, ideally nearer to 200psi. Cylinders should be more or less balanced. Some variation is to be expected, you'll likely find 2 & 5 are down compared to the rest. Any variance beyond 10-15% isn't ideal but not neccesarily a big issue.

Checking the injectors are getting volts and switching has already been suggested somewhere - pop your 'scope on the low side of one injector and see what you see. Should be an active low PWM drive, rest is 12V, duty cycle at cranking will be pretty short - expect pulse length in the mS range.

I'm running out of ideas now.......


...and yes, those rear bank plugs are awkward!, but at least you don't have to remove the charge cooler or supercharger to get at them.......(obscure reference to my current project )

 

Thanks for the detailed answer Chris - wow - another AlfaHead who knows a PWM signal when he sees one!

I think fuel is OK - have tried the pumping test and there is lots of pressure there when releasing the JubiClip at the reg.even after standing for a couple of days, so no leaks in the feed. And damp-ish plugs.

Haven't got a timing light, but I expect I will be able to find one somewhere locally/friends. I could put the timing wheel signal on one trace and the plug lead on the other (proximity probe!) but that's probably getting a bit too elaborate - never try to accuse me of doing things the easy way

I haven't yet discovered how to get the injector connectors off (??) but with the lid off the ECU I can get at any signal I want (inside in the warm! - the car is still stuck out in the road where it landed from the tow 5 weeks ago But see comments about wet plugs...

 

The AMP connectors can be a swine if they don't have the release loop in them (and the stock ones on our cars don't). You can either try easing the spring out of the way or just pulling hard. They are supposed to pull off OK with sufficient force, but as they age, they tend to go brittle and you often end up breaking the spring seat off. Not ideal but not the end of the world if you happen to do that. New plugs are readily available from the likes of VWP.

Make sure that the plenum earth strap is intact as well - the ECU loom earths to the plenum, but this is rubber mounted so relies on the earth strap from plenum to head. The 12V 164 did the same, but has a solid mounted plenum so no problem there.

Again, go back to the basics. Sorry to keep harping on about it!

Shame you are so far away - I'd be interested to have a look at this one!

 

Thanks Chris

I had an exploratory pull at the connector, but stopped short of, as I thought, breaking it or pulling the wire out. Not that I can't replace a crimp or solder joint easily enough, but a shorter wire wouldn't lie the same way on the loom, and original is best...

Trouble with the basics, I think we've exhausted them twice over, and friends who initially came to help have drifted away with lack of any exciting progress Luckily and strangely, I seem to have an inexhaustible supply of curiosity and fatalistic optimism, probably as a result of some exotic virus impregnated into the seats and carpets back in a secret Alfa finishing workshop. And there's no known antidote

 

By basics...I mean take both cam covers off, take the cambelt covers off, take the OS wheel and arch liner off then see what you've got. (I can't recall....does the 155 have those handy scribe marks on the camwheel centers like the 164 does? I've got a spare engine in the garage and will try to remember to have a look this morning. If it does, then you can use the 164 camwheel template to check cam timing and it saves a lot of agro if you can.)

Next, pull the inlet runners so you can ease the fuel rail off complete with injectors & wires, crank it over and look for sprays of fuel. Be careful of course and don't forget to unplug the coil pack before doing this.


With respect, if you haven't put a timing light on it to check spark timing, nor checked that the injectors actually squirt fuel as they should, then there are still basics to look at. I know these are highly unlikely problems...but you seem to have eliminated pretty much everything else...and there is still that compression check to do don't forget.

And again, just because it's been checked, don't be shy of another look with fresh and critical eyes. Again, ask me how I know - for example, the rear bank cam timing mark on one of the 164 motors I have is 1 tooth out. This is the mark made at the factory. That caused some confusion.......and I'd checked it many more times than once.

I'm not trying to be p155y here - just observing that these are fundamentally simple things, and don't need all that much to kind of work....and yours won't do even that, so there simply has to be something fundamental wrong.

Tried pouring some fuel of some kind straight up the inlet yet?

Fuel, air, spark at roughly the right time, mechanical bits in roughly the right places, BANG. It might not be pretty, but it will make a noise.

Honestly, don't over-think it. I applied 20+ years of electronics and electro-mechanical systems 'expertise' to a problem I had with mine, after a very long time and an awful lot of testing, much of it as in-depth as you are doing, I eventually returned to about the first thing I had tested - a fuse. Turned out it was cracked (not blown) so made intermittent contact. Guess what, every time I tested it, it was working......

Keep going....

 

Sorry, didn't get to the garage this morning - I'll have a look tomorrow.

Meanwhile...you WILL solve this, and I bet all us internet experts will be kicking ourselves when you tell us what it was......

 

Thanks Chris

I like p155y, just how I feel about it most of the time, and now it's snowing again, just when I was planning on lining up the local radio net to shove me out of the road(!) into the drive. One of the guys is the owner of a set of large Hex keys which fit the cam cover bolts - time I got my own set, or some socket keys...

"Inlet runners" is a term I'm not clear about, and the coil is currently on the bench, so reducing the fire risk - others have suggested the injector check, but that was at an early stage, so it seemed a bit drastic at the time - not so now. Are the injectors just dropped into the ports in the inlet manifolds, or do they have to be individually unscrewed? And presumably the regulator comes off with it after the breather pipe has been disconnected from the plenum?

 

What I called the inlet runners are the 6 chrome (unless it's gone rusty!) tubes going from the plenum to the two inlet manifolds. It's usually less of a struggle to get them off if you first remove the plenum.....you can see where this is headed, can't you!

Only trouble you are likely to have will be the Allen bolts holding them to the maniflods - they have a tendency to be overtightened and rounded. Also, the gaskets between the flanges of the runners and the manifolds usually fall apart...but a wee squirt of goo will do for assembly.

The injectors are clipped to the fuel rail and 'just' push into the heads with rubber O rings to provide the seal. The 4 bolts holding the two rail halves to the heads are all that's needed to keep it together, as the tendancy is for the engine to suck the injectors into place of course. I say 'just'....after a few years they do tend to grab hold a bit, so removing the whole thing might be tough - you may be forced to un-clip the injectors, then pull the rail off the top..same deal though, small O rings that tend to grab on after a few years. TBH, I'm happier disturbing the head side than the rail side if I'm not replaceing the O rings, as it's only under slight negative pressure when the engine is running, whereas the rail side has 3 bar fuel in it. Worst-case and new O rings are cheap enough. Watch out that none of the pintle caps fall off the ends of the injectors and end up inside the motor. They are only plastic, but I'm sure with bad luck they could do some damage.

Yes, just pop the regulator 'control' pipe off the plenum and the whole rail assembly can swing up and away without disturbing too much. Unless you've already replaced them, no doubt the rubber fuel lines will start weeping at this point!


Having said all the above, I'm really not sure, but you might just be able to pull the rail without removing the runners. I can't recall if I have ever tried that - I'm pretty sure it won't work though as there isn't a lot of clearance. Worth a quick look before getting too carried away.

Actually...thinking on it, if you did remove the runners, you would be able to look inside the inlets and see the injectors spraying (or not) without having to pull the rail, just need a volunteer to turn the key for you.

Aint cars great.......

 

Yup, especially in the snow. got all that, thanks. A bit more disassembly than I want to do out in the road, I think, so the priority now is to get it moved.

if I get my little in-telly device sorted, I could look inside and film the event, provided I get the clearance the same as a spark plug - this is beginning to sound a bit dangerous, so maybe not!!

 

Nope, 155 camwheels don't appear to have a useful external mark like the 164

 

Looks like I've ripped the teeth off the cam belt, as the front camshaft (at least) is not moving. Not electrical at all, after all the messin' around.

What fun, anybody got a set of cam locks for the 155V6/2.5 for sale or hire? TotallyAlfa have them but I'm not sure they are the right ones - I'll be getting in touch to ask them.

Where's the best place for the belt/tensioner kit? Any recommendations?

OW!

 

No camlocks required for the 12V motor. Just use the crankshaft timing marks (dial gauge the TDC if you like) and the marks on the cam caps.

Before you spend any significant money, I'd check to see if you've done any internal damage to it. Buy a new belt from your local factor and pop it on, then turn it over by hand to make sure it all works OK, if yes, then crank it and do a compression test.

The biggest issue you have to solve is getting the cams and crank on the marks from where you are now. It's an interferance engine, so you may have to 'walk' crank and each cam around carefully to restore timing. Either that or take the heads off!

Search on AlfaBB - there is a good guide on how to do this. It's for the 164 12V, but it's basically the same.

If you find you have good compression on all 6, then enjoy a big sigh of relief, then go buy a new waterpump, new tensioner and carefully(!) read up on how to set the tension with these crappy thermomechanical tensioners we have.

EB are usually pretty good, but there are other places. Got my last pump from Shop4Parts IIRC.

 

Thanks Chris

That saved me 50 quid for something I don't need! I have a dial gauge and compression gauge, so next a new belt, and as you suggest, a water pump because contrary to all the embarrassing evidence, I DO believe in Sod's law

I should do, considering the number of times it catches me out....

I think I have an article on belt changing, maybe the one you mention, but I will have another look for that one as well.

Can you explain further "marks on the cam caps", or will it be obvious when I get the lids off?

Cheers.