points gap confusion

[Varsas]

Hi all.

I have a very slight misifre on my S3, 5MB, 2.25 petrol landie. It'll usually idle OK, but if you rev it it'll cough and splutter a bit. It actually drives very well, but occasionally you can hear and feel it stutter a bit, especially at high loads and low revs.

I have checked HT leads (by swapping them for known good ones) spark plug condition/gap, timing, fuel/air mix, compression. All are fine. I have also reset the vale clearances, when I got the car there wasn't ay clearance on any of the valves even with a stone cold engine!

The next thing to check (should have been one of the first) is the points gap. If that's OK then I'll replace the condenser, then the coil.

Despite owning classics for the last 10 years I've never had to check or set the points gap, my other cars had electronic ignition, but since I now have two cars with points I'd better learn. I was assured it was quite an easy process but I've still managed to get very confused.

The haynes manual says to '<rotate the engine> until the contact breaker arm is at the peak of one of the four cam lobes'. How do I tell when that has happened? Since I didn't know how to do what it wanted I thought I would just rotate the engine until the points moved as far apart as possible, and then measure that gap. That doesn't seem to work, at no point is there any gap between the points. I span the engine one half of a revolution (checking the points after every small movement) and the points where closed the whole time. I then span it over on the starter a few times, after every rotation the points where still touching.

What am I doing wrong?

Am I checking the right thing, the gap between the two parts pointed to in the arrow in the picture (the moveable arm and the fixed piece)?

How do I get the engine in the right place for the points gap to be measured? Can I do it by looking at the valves?

Are my points so badly set that they are touching all the time? (this would explain why I couldn't set the timing statically, I tried using a test lamp between the LT side of the coil and earth, but the lamp never came on. I have used this method successfully before so I was a bit confused).

Thanks in advance for any help.

[Bowie69]

Having never seen one, I assume that is a Ducellier dizzy (red cap)... but the principles hold true, you need a certain gap between the pointsotherwise you won't get a spark and it won't run

There should be a 4-lobed cam on the main shaft, which I can just make out in the photo, this pushes on the white plastic finger and opens the points. The cam in your photo looks VERY smooth, i.e. worn, but wait for confirmation as I said, I am not familiar with the Ducellier distributors...

To set the gap loosen the screw just beyond where your white arrow is pointing, and move the plate until you see a gap, your test bulb should go out now

To get the cam in the rightplace, turn the engine slowly by hand, the cam high spots should occur twice per engine rotation, watch to see the white plastic finger being pushed out by the cam, when at it's highest this is where you adjust the gap in the points, if they are still closed then your engine will have been having a hard time running

If you haven't adjusted them or replaced them, it could well be worth replacing them now with a new condensor at the same time -inspect the points surfaces for pitting and corrosion.

[Varsas]

Ahh..OK, I see what you mean. So the lobes are actually on the shaft itself...should have seen that.

No idea what the distributor is, I assumed it was lucas. It has a black cap. I have had a look at the surfaces of the points, they look OK. Fairly smooth with no deposits. The inside of the dizzy cap had plastic flash markings covering two of the contacts. I cleaned them off. With that, this points issue, 0 clearance on the tappets and timing a mile off it really is a wonder this car ran at all...no wonder it overheated on the way back from picking it up!

I have just been out and checked. Even with the top of the can lobe pushing the arm away there is no gap at all, certainly not one I can measure with a feeler gauge. If I push the arm toward the gap it doesn't move, if I pull it out slightly and release it I can hear it 'tap' against the other part.

As you say the lobes are very indistinct, I can't help feeling that if I adjust it out to 0.4mm they'll never touch. We'll see. perhaps this dizzy needs a different gap?

If I need a new dizzy would this do?

http://www.ebay.co.uk/itm/LandRover-2-25-2-5-Distributor-ETC5835-/330606178988?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item4cf9a9f2ac

Thanks for your help!

[Bowie69]

*IF* you need a replacement, have a look on the side of the dizzy body to confirm type, you'll see something like this:

That way you can be sure to get the right one.

I'd be rather suspicious about that egay one, far too cheap to be any good IMHO.

[Varsas]

Will do. I'll have to clean it first of course...

Right, thanks for the help. I have now set a points gap. The car still runs but it hasn't improved the misfire/stuttering. I'll re-check the timing, then replace the condenser and then coil. If neither of those help I'll be back...

Off to check the gap on my XJ6 now. It has very similar symptoms to the landie...

[SeriesEwan]

thats definately a ducillier Dizzy, look in the BACK of your haynes manual for all the suplimental revisions & you will find out what the correct points gap / setting routine is for that type ( if you read the standard ignition part & set it up as a lucas it will run like a dog )

to be honest setting the gap only gets you in the right postcode for ignition timing, Especially if the lobes are worn, What changing the points gap actually does it alter the dwell angle ( the time it takes to charge the coil ) get yourself a dwell meter ( http://www.maplin.co.uk/automotive-digital-multimeter-with-inductive-pickup-222059 ) & set the dwell angle to the correct figure ( this can be found in haynes )

[Ally V8]

Series petrol engines are just about the best candidate I can think of for fitting electronic ignition such as Lumenition.Most replacement points and condensors supplied now are very poorly made,so even if the rest of the distributor is good the results wont be 100%.

My old IIA runs like a modern engine with Lumenition and an SU carb,even though its pretty much worn out.....

[secondjeremy]

I think your cam lobes are very worn. 4 cylinder ones are generally much 'lumpier' than that.

You can only gap new or freshly filed points effectively. the reason is that as the engine runs the sparking across the points caries metal from one to the other - so that one point gets a lump on it and the other - a crater. At the very least the 'lump' must be removed so that you can get an accurate gap.

As has been stated the points gap determines the 'dwell' but in itself this isn't desperately important on a 4 cylinder - as after all the same coil and basic setup worked well on V8's - which of course have twice the number of sparks. It is however a useful check that you've got the points set correctly.

The spark occurs as the points open. The close up with wear - so the spark becomes retarded.

[Les Henson]

Ducellier distributers are very poor quality no matter how hard you try, the timing can vary by as much as 10-degrees. I had this same problem with a customers S3 and eventually got a krypton tuner to look at the engine. He confirmed that the timing was at times 9-deg out. I fitted a Lucas distributor off an old Mini and the problem was gone. Electronic ignition kits are by far the best and make a dramatic difference to starting and general performance of the engine. If the centre shaft of the distributer has any side play in it - that's your problem.

Les.

[Varsas]

Thanks for the replies. My uncle is into landies and has said the same thing, i.e. ignition is a bit of a weak spot. I'll look at fitting a luminition kit (my Stag has one and is seems to work well). I do have a dwell meter but leant it out and haven't got it back yet. It'll have to wait till next week.

I certainly see what you mean by the cam being worn, I looked at the one in the Jaguar and it's much more pronounced.

[Ally V8]

You wont be wasting money if you go for a system like Lumenition,I've been using them since I was 19 on my first v8 Range Rover.(Totally transformed long term reliabilty)

My brother has just fitted it to his 1933 austin 12/6 out in Oz,he reports that it runs better than ever before.Wear in the dizzy bearings no longer matters,(Timing scatter gone) plus the spark stays the same over time,not getting later as the points close up or pit and piling resulting in poor switching.Even old and very worn engines can run better than they ever have.

I ride Pre65 and twinshock trials bikes,decent and accurate sparks have made tons of difference to how old British bikes run and their overall reliability.

[Varsas]

Maybe I should consider doing the same to the Jaguar...