The Marellii distributor should be aligned with the arrow on the rotor pointing the notch in the distributor, all aligned with a rib on the Jack shaft cover plate, per Bywater. V12 IGNITION SYSTEMS / AJ6 Engineering
This car hasn’t run in years. It ran when I bought it, I took lots of stuff apart, and it never ran again. It has spark, it has fuel, it just doesn’t run. When it was trying to run, it would fire faintly and rarely and stumble a little here and there… like it was a gear tooth out. The first alignment photo is how it was last time I tried to start it. The second is one tooth different, but looks even worse.
In his picture, see the three Allen head screws in the slotted holes? That’s the adjustment. The top portion of the distributor turns in relation to the bottom. Your screws are missing, so it ought to turn freely, unless the two halves are corroded together.
The screws are out so I could demonstrate the rotor alignment in two different gear positions. I’ve set the the body to where it would be in either case, almost fully cocked to one side, with the notch along the rib. It’s the rotor that isn’t lining up as I expect…
It is, but so is the one in the top picture (Sobev) and his is correctly aligned.
Having said that, why not rotate the top until it aligns? Nothing to lose.
Also, when your trying to run it put a timing light on it and see where you are.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
6
I suspect that the sprocket for the jackshaft was not lined up correctly when the timing chain was installed. Either that or it has skipped a tooth, which they have been known to do followed by the teeth all getting sheared off.
Rather than taking the timing cover off – which would be work – just adjust the distributor base until it aligns properly with the little notch. The rib on the valley cover will be wrong – but who cares? It’s the alignment of rotor to cap that’s important. As long as the jackshaft sprocket doesn’t slip again you should be OK.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
7
A timing light is of no use whatsoever on a Marelli car.
Yours truly’s name was butchered a bit :-)) , but the information I’d provided in the past is correct.
On a Marelli car, one needs to also verify the timing mark on the damper.
If not, what @BobPhx suggests is necessary.
My own pictures are in the albums on the “old site”, this one is courtesy of Alan, aka @lockheed1
Goes without saying (but that never stops me) that the plug wires must be routed to the proper towers on the distributor cap for any of this to matter…
The distributor does not control ignition timing in the Marelli system. The Marelli ignition system with the input from the crank position sensor does that job. All the distributor does is send the spark to the correct cylinder.
I would start by verifying that the damper mark is in the correct location; the outer ring is known to slip in relation to the hub. You need to ensure cylinder 1 on A bank is at TDC with both valves closed (cam setting tool will locate). If the damper ring has slipped on it’s hub and was used to locate the crankshaft, the piston will not be at TDC. Not knowing if the timing chain has been messed with, it is something to check. Might also explain the jackshaft not being right…
If far enough off, cranking the engine in that state could bend valves.
Hmmm. We say the timing cannot be adjusted, but if I rotate the distributor isn’t that timing? That’s how you adjust the timing in any car I’ve ever worked on.
I’m definitely gonna give it a shot, that sounds way easier than taking the timing cover off the front. Someone has been inside this engine, it’s got some weird pink paint dots and double dots in places.
No.
The ignition ECU knows where TDC is because of the crank position sensor. It knows what the RPM is because of the Engine Speed Sensor. It then looks at its map and fires the spark at the appropriate advance. On other distributors the firing of the spark is controlled by an optical or magnetic sensor, or breaker points, in the distributor. Rotating the distributor changes the relationship between these triggers and the posts on the dizzy cap, advancing or retarding the spark. The mechanical and vacuum advance mechanisms also change this relationship. This can’t happen on the Marelli unit because spark trigger is completely external to the dizzy.
Rotating the distributor only aligns the rotor with the appropriate terminal/tower in the cap; has to be correct to allow good spark energy transfer at all advance situations.
