Hey there,

I need to remove my dizzy (again) to get a better access to certain parts and wanted to quickly ask:

the dizzy itself has two markings. One on the lower casting and one on the rotor arm.

If I remove the dizzy, but rist put the engine on the TDC position so that all the markings align, then it doesn't matter really if the dizzy is put back in the same position, as long as the marking of base and arm line up, right?

Sorry if I'm asking this, but I've only ever had (if a dizzy) a simple one which was mounted to the camshaft on an OHC engine. Otherwise all my cars have had COP setups...

Cheers

Damien

 

Yep.

If the markings are aligned prior and then again after, it will be as it was.

 

And then it doesn't matter where the rotor arm is poiting, a long as the markings line up...?

 

Damien,

Have a read of this I wrote years ago.

I think it will answer all you need.

Refitting the V12 distributor.pdf

 

Daim
Without a pic it is hard to know exactly what you mean. But, as Grant indicated the best way to ensure all is OK is to ensure (i) the engine and (ii) all parts of the dizzy are put back exactly where they were when removed.


The only thing that matters on the dizzy is that (ASSUMING the engine is not rotated while the dizzy is out) the rotor is pointing exactly where it was pointing before removal. The rest of the dizzy does not "know" where it is. When I removed my dizzy this is what I did:

• marked casing against the engine jackshaft cover (so I could be 100% sure the dizzy body went back where it was)
• Marked the rotor arm with a scribed line and marked the plastic casing the cap screws down to with the same line (so I could be sure the rotating bit on the dizzy went back exactly where it was)
• I did NOT turn the engine. But IF you do (and why?) you have to find a way of ensuring the engine is (a) in the same place and (b) on the same camshaft rotation as it was before removal. There are probably lots of ways of ensuring this, but probably the most reliable is to have a cam cover off and scribe a line on the cam chain sprocket across to the engine casing.

Greg

 

Does this all count for Marelli engines as well? As the dizzy doesn't need / won't take manual adjustments...!?

 

No idea, BUT if you do all that you can be 100% sure it went back exactly where it came from.
Greg

 

I'll just put it where it used to sit... Luckily there is a marking on the front pulley for this stuff (at least on the Marelli)

 

@ Greg

Greg, this is the "marking" in the dizzy base I meant... You can see a little cut in the body. As I had the flywheel in place, the arrow on the rotor matched with that little cut out...



And as you can see, the dizzy is totally empty...

 

That is true, but that mark does not guarantee the camshaft will be in the right place, and hence the timing will be correct, as the crank turns twice for each camshaft rotation. hence the need to mark the camshaft sprocket if the engine is turned, dizzy out.
Greg

 

Yes, but the dizzy body to engine fixings are in slotted holes, so a scribe across the mating surfaces is still a good plan. That dizzy body can be replaced in a slightly, but sufficiently, different position as the slots will allow that to happen.
Greg

 

Yes, that is what I mean. I can technically align the body to the rotor arm (to a certain degree) to make sure the cap fits correctly, if you know what I mean... Quite hard to describe. My English seems to be getting worse and worse... Need more time back home in Britain...

 

But then, why should the timing be out?

I've only turned the engine clockwise (as you are supposed to) and haven 't moved it without the dizzy in place!?

 

"I've only turned the engine clockwise (as you are supposed to) and haven 't moved it without the dizzy in place!? "

I expect Grant and I got the wrong idea from an earlier post Daim.
"If I remove the dizzy, but rist put the engine on the TDC position so that all the markings align, then it doesn't matter really if the dizzy is put back in the same position, as long as the marking of base and arm line up, right?"

You seemed to be saying you would turn the engine once the dizzy was out. If you do not turn the engine when the dizzy is removed, then obviously you just need to scribe a line oacross the dizzy casting to block join, and also on the rotor arm to casing lineup. Then when you replace the dizzy it will all be as before. As long as the engine is not turned, the camshafts will not move. If it is turned, they will, hence the need to mark their position.
Greg

 

Ah, sorry, no, that got mixed up in the lines...

No, of course, only remove the dizzy after the engine has been put on "TDC" or how ever it is supposed to be.

 

With cylinder 1A at 10° BTDC on the compression stroke the rotor should point to 1A dissy post. Rotating a Marelli dissy in its mounting holes has NO effect on engine timing, like it does with a Lucas system.

 

How to tell about how many degrees the engine is BTDC? The little plate as fitted to the Lucas cars isn't on the Marelli. My front "tag" which is around the sensor, doesn't have any marks on it (at least none I can tell)...!?

Is there something else to look for?

Regarding the motion in the holes: I would only use that to turn the dizzy in order to compensate a possible misaligned tooth in the dizzy drive... There isn't much play. I am aware that manual corrections of the Marelli ignition don't work (which is why I wanted exactly this ignition system over the Lucas system, because SHOULD I take it somewhere for an MOT/TÜV, they won't play with the dizzy).

 

My damper is marked 10° BTDC. If you turn the engine so the rotor is in the middle of the 1A post before you remove the dissy then make sure the engine is NOT rotated it will go back together at the right spot.

 

Warren
Please explain further! The dizzy rotor shaft is turned by the jackshaft; if the dizzy body is turned relative to the rotor shaft, surely that changes the point the spark hits the cap posts at?
If the dizzy/rotorshaft/cap and HT leads as a unit is replaced in a different orientation, without changing it's relative positioning between the 4 items then I agree, timing is not affected; but this is true in any dizzy in any engine, (I think !).
Greg

 

It doesn't affect much, as the contacts of the rotor arm are long (about 12-13 mm, maybe even longer). So IIRC it provides enough contact area for the ECU to trigger a spark. If you rotate the dizzy cap, then it won't affect it, as the spark will still be triggered by the ECU and the arm has enough surface to cover an ever wider span of degrees before/after TDC to fire than needed.

Look at the rotor arm in this picture:


The contact patch is long/wide. Wider/longer than the adjustment possibilities of the dizzy holes where it is screwed through to the block. The dizzy itself it totally hollow and only has the rotor arm(s) in it which is directly connected to the shaft with no possible adjustment (like the Lucas vacume operation has) so the rotor is always spinning in an unadjustable rate. The contacts touch longer but the spark isn't triggered until the ECU tells the coils (2 modern compact coils) to fire. So you can adjust the dizzy as much as you want, the ECU has the last word... It can fire upon initial conatct with the rotor arm, it can fire in the middle or it can fire at the end. The entire contact patch of the arm is used to ignite the cylinders (if you look at the width that also explains why they needed to use 2 rotor arms).

The only way to "adjust" the ignition timing, is by using a bracket to move the front crank sensor around. You then "fake" a different timing setting and this will allow earlier/later iginition...

I hope I explained that understandable.The Marelli ignition basically has nothing in common with the Lucas setup, apart for being in the same position