Distributor driving gear, off by one tooth?

Hello all, I am coming to the end of the rebuild of a XK engine for a1975 XJC, and it will simply not start.

I am concerned that I may have set the distributor driving gear off by one tooth (or 2).

Here is a video that explains the situation (8° BTDC).

Here is a photo of the distributor gear on TDC 0. Is it off??

FYI, when piston 1 (rear of engine) is on TDC (confirmed with dial gauge), camshafts are set with the setting tool, crankshaft pulley set at TDC 0.

Your wisdom and guidance will be greatly appreciated (before I dump this whole thing in a lake… :wink: )

Here’s mine for comparison.

You’re at a point where 1 and 6 are still interchangeable. Take a look in the manual and see if the rotor points to position 6 when both cam lobes are pointing away from the valves, by inserting your distributor you‘ll know.
Wardell‘s looks better.

Compared to yours, I am indeed off… :frowning:

That would change nothing, the problem would remain the same. It is not 180° off.

Yeah, I somehow focused on the last part too much. Sorry. It seems off by a tooth or so. The question is, can you live with it? Since it won’t start what I will be doing next week is that I will turn the engine by hand and observe the spark plugs (out but wired and grounded). That gives me firing order and timing so if it’s roughly at 8° on the damper and not one turn out it shouldn’t be the ignition system. If you run out of space with the vacuum capsule you’ll have to change the wires and readjust…
But then again yours is upside down compared with wardell. So one of you is off by 360° And a tooth.

Yes, it appears that you are.
I had this problem many years ago with a different Jag.
I simply moved the plugs leads around by one position. No need to strip it all down.
Mine looks the same as in the workshop manual, so I’m pretty sure it’s right.
I don’t think yours is 180 degrees out, just one tooth.

I tried that, does not help, the ignition point falls between 2 spark plugs wires. If the rotor had a tip that allowed for longer contact with the plug spot on the distributor cap, it would work.

Look like a sump off job… :frowning:

You can always turn the distributor though? After all it’s not much if it’s only 1/12th or less?

Eric your drive is off 180 compared to the factory setting, but it matters not a jot ! with 1 and 6 at TDC and the cams positioned with the cam setting plate insert the distributor and position it so the rotor points to a contact pole, then connect number 6 plug wire to that pole and continue 24153 in a counterclockwise direction looking down at the distributor. As you will be setting at TDC turn the distributor clockwise a tad to advance to approx 10 degrees, if the engine kicks against the starter then back the distributor off .
If the engine does not show signs of life the prob is elsewhere.
Waste of time dropping the sump to reposition the drive shaft.


What Peter said. The distributor does not know which plug wire goes where. With the engine at TDC, either #1 or #6 has to be on compression and ready to fire. For the sake of example, let’s say that’s #6, at the front. Lift the cap and note which terminal the rotor is pointing to, or is about to point to. Make that terminal #6, then proceed around in order 2-4-1-5-3.


Thank you for all the advice folks, but I think I am failing to explain what is happening here. Watch the video and you will see that regardless of the position of HT leads, or the rotation of the distributor body, the electric contact been the rotor and a HT lead cannot happen at any of the 6 times when the rotor connects to one of the contacts in the distributor cap. It is as if the distributor cap is wrong (which makes no sense) or the position of the rotor is off vs everything else.

Watching the video certainly indicates that you are not going to get a spark to any cylinder with the set up you have. I have to think you are correct in that the sump is coming off.

Thanks Robin,
Next I have to find a way to be certain of the position the distributor gear has to be on to be correct. One tooth, two teeth??
I am amazed that a setting of this importance is not positively indicated on the block with a stamped marker or something…
I thought I had done it spot on, clearly not…

The final position of the ‘D’ when you are looking down the dissy drive is documented in the manuals, if you still can’t get a spark when that is in the correct position then you have a problem within the distributor itself.

Yep, and I thought I was following the instructions to the letter… :frowning:

Distributor just came out of the box, expensive piece of modern technology.

after, and even if, verify fat blue spark at plug

I would fit a points dizzy if I had one at hand, and see if you can start the engine

less confusing, you can rotate the dizzy to max retard and advance

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Hi Eric - it doesn’t help that the offset of the slot in the distributor drive (which allows the distributor to be installed one way only) is not that obvious in the manual’s illustrations. My reading of it was that the clocking of the slot was what was being illustrated. I was lucky to get mine right first time in ignorance of this detail…

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Eric in your video you refer to number 1 as per instructions, please make the contact point that the rotor is approaching number 6 and wire the cap accordingly, if this does not work then change number 6 to the contact that the rotor has just passed this latter suggestion seems daft but give it a go.
Changing the drive by any amount of teeth will not make a ha’path of difference to the position of the rotor relative to the green light.
This comes down to stating the firing order as 153624 instead of 624153, unless 123 have worked this out and have cunningly configured the distributor to fire on 6 but instruct to time on 1.
but I doubt it. !!!

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Hi Eric…there could be slight confusion with piston 1 & 6…but whichever one you try to fire it must be on its compression stroke…1 & 6 will both come up to tdc at the same time but only the one on its compression stroke will fire…yes your distributor drive is not in the correct position as per the service manual but thats not a problem…just fit the 123 and turn it till is led comes on as you are doing…then fit the rotor arm but make sure that the ht lead the rotor points to in the cap goes to the piston thats on its compression stroke…take care with fitting the cap its very easy not to have it fully fitted in position and the cilps still will fit…also taking the permenant power (red) directly from the coil can cause problems…better to take a feed from the fuse box that is controlled by the ignition…Steve