Technical How do I fit new (contact) points?

[markoibook]

Hi peeps,

After my car broke down the other day, and the AA man helped me out, I need to fit new points to my mk1 Uno 903cc.
I have a magneti marelli distributor, and am due to do it tomorrow, after I've picked up the new points from Camberley AF.
Can anyone give me any guidance or advice? It looks relatively straightforward, and the AA man was very helpful - but are there any hints or tips you can give me?

Thanks in advance,

Marko

 

[custard]

god points,havent had a car with points in yonks.if its cassette points they pretty much drop in.
if its older style points its a bit more fiddly but not too tricky

 

[markoibook]

Cool - it doesn't look too bad.
Just 2 questions tho - the AA man rocked the car back and forth when looking at the points, do i need to do this too? And in the haynes manual it says about removing the vacuum advance module - is this really necessary?

 

[markoibook]

Um, ha ha. Oops.
Just returned from Camberley AF and realised that I had the wrong points - turns out the distributor is ducellier - which is odd cos I swear the cap and rotor arm are magneti marelli :S - well they look different to the pic in the haynes book.
Anyway, after the confusion, I shall be picking up the right points next weekend, so in the mean time, any advice would be greatly appreciated.

 

[markoibook]

Anyone remember points?

 

[Timm]

The AA man was probably rocking it back and forth to see the points opening and closing.

Just fit them, then rock the car as he did until the points are at their furthest gap , then measure the gap with a feeler gauge.

Adjust if necessary. The correct gap should be in the Haynes manual somewhere.

 

[Timm]

Anyone remember points?

Just dug this out from an MG site but it will still apply, hope it helps.

Distributor
To work effectively the distributor must be fitted with a set of contact breaker points that are in good condition and correctly gapped. Remove the distributor cap and examine the surfaces of the contact breaker points. If the points are severely pitted or indented with tiny craters they should be replaced. If they appear to be in good order then check the contact breaker gap. Put the car in gear and push it forward to turn the engine until the cam of the distributor drive fully opens the points, now you can insert a feeler gauge to measure the width of the gap. To adjust the gap it will be necessary to slacken the set screw in the centre of the points so that some movement of the assembly is possible. Then insert the flat blade of a screw driver into the slot at the end of the points just before the condenser and use the dimples in the base plate of the distributor to open or close the contact breaker gap.

breakergap


Adjusting the contact breaker gap by using a screwdriver to move the contact set against the base plate.

measure gap


Using a feeler gauge to measure the gap when the points are fully open on the cam, it should be between .014 to 0.15in (.35 to .40mm) for most MGB engines.

Contact breaker points
Removal and replacement is quite straightforward but take careful note of how the points are fitted and the position and route of the wiring. When the new set is in position make sure the distributor cam is holding them in the fully open position and adjust the gap as described above.

centre screw


Points are fitted onto the base plate of the distributor with a centre screw.

breaker arm


Points are opened as the cam pushes against the sprung contact breaker arm.

 

[Sav_M]

Hi Mark, just noticed this post or I would have offered some advice earlier.

The last time I changed points was 3 years ago on a 92' Uno formula, but this had the Marelli dizzy, as did my old Mk1 formula........

......the only Ducellier equipped 903 Uno I changed points on was my Mum's, and we're going back about ten years now.

Get the cap and rotor arm and plastic shield off first anyway................

So from what I remember it was indeed straightforward enough. The Ducellier points should be in two pieces I think, a small base plate, and the spring loaded part with wire attached.
This section is held on by a verry fiddly spring clip which should be carefully pulled off using long nosed pliers, there is a small washer under the the clip, so take that off as well.

Disconnect the wire from outside the distributor body, now this section off the points should pull up off the post.
The base plate part is held on by a small screw, remove the screw and washer and lift this out.
With the points out of the way just check that everything is clean inside the distributor, it's also worth (lightly) lubricating the advance mechanism under the plate.
The rotating cam in the centre should be cleaned up and lubed with a very light smear of grease or petroleum jelly. (just enough to make it slippery really)

Now you can fit the new points, it's worth cleraning the contact surfaces of these as sometimes there can be a film of oil on them for storage purposes.

Fit the small base plate first, remembering the washers, tighten this only temporarily for the moment, as this is the adjustment screw as well.
Next fit the movable spring section, down onto the post making sure everything engages as before. Route the wire out through the body and connect it up.
Now you can fit the retaining washer and spring clip onto the top of the post.

Just need to set the gap now........on the central cam in the distributor you will have seen that it has four lobes, rounded corners as such...what you need to do now is ensure you get one of these lobes turned so it comes into contact with the plastic heel on the movable part of the points. (meaning the points are fully open)
To move the cam the engine needs to turn, and the usual method is to put the car in gear and rock the car back and forward whilst looking for when one of the lobes fully opens the points.
Once you do this you can set the gap by loosening and moving the base plate until your feeler gauges are a nice sliding fit. (not tight, just a small amount of resistance)
Gap is about 0.40mm, check the manual to be sure, but 0.40 is an inbetween figure which is pretty safe.
You might not get it straight away, but once your happy, tighten up the little base plate screw.
It's worth re-checking the gap at this stage as sometimes the base can move.

Now you can replace shield, the rotor arm, and the cap.

It should now start, but I always prefer to set the the dwell angle as it does make a difference.
I won't go into that just now though as it sounds complicated enough as it is.

It's easy enough really.

Hope this helps a bit, if you need any clarification on anything just ask.

Cheers,

Sav

 

[Louie Bee]

Nice post Sav – Rep awarded

I have one or two things to add o sorry I’m late):-

Switch off ignition off first.

It’s a good idea to replace the condenser when you have the points out. It’s the cylindrical part on the outside of the distributor that the point’s low-tension lead plugs into. Undo its fixing screw and washer, unplug the points from it (if you haven’t already), fit new one (opposite order). Make sure it clamps tight enough so the condenser doesn’t slip through the mountain bracket. If it dose, remove, bend bracket inwards a bit, and try again.

The Haynes manual says points gap is 0.37 to 0.43MM – I used to use 0.4MM.

The screw holding the fixed part of the points fixes an into an aluminium base plate – be careful how tight you screw it – not enough and the points will slip – too much and you’ll strip the thread.

Take care to ensure the points spring doesn’t touch the side of the distributor when in place else It will earth out and your car won’t start .

Good Luck

 

[markoibook]

Thanks guys - all very helpful - and a very indepth explanation there by Sav!
All sounds straightforward - I have my haynes and feeler gauges too, and that was the way I thought I had to do it, but always helps to check with someone that has done it before!!!
Louie - as for the points springing too far out and earthing - this was a problem I had about a month ago, and the AA man insulated it with tape. All was well till last week - and it looks now as tho they need replacing. Have has a new condensor put on already - it was the only way the second AA man could fix my car enough that I could drive home. He did several tests and says its definitely the LT side of things where the problem lies, so really the only thing left it could be is the points - the coil is fine. So heres hoping that new points fix it. If it does, I will be very pleased and she should run just nice - she's had new plugs, leads, rotor arm, cap when i serviced her 3000 miles ago.
Thanks guys, and wish me luck! I shall report back after I've had a go on Saturday!!!

Marko

 

[Louie Bee]

Let us know how you go on .

 

[Sav_M]

Hey Louie thanks for the rep much appreciated.

Some good extra tips there as well.

Replacing the condenser is always worth doing when changing the points.

Good note on the base plate screw, and every one I've had has had a chewed up screw head as well, so correct sized screwdriver a must.

Mark....hope you now have a better idea of what you're going to tackle now.
Just a matter of taking your time and being careful.

Best of luck,

Cheers guys

Sav

 

[markoibook]

Hey guys - thanks very much for all the advice - very much appreciated.
Well I popped up to Cafco this morning to pick up the correct points (the ducelier) and fitted them. Took me about 40mins to 1 hour - most awkward bit was trying to get the plastic lump that slots on to the distributor to push down enough for the spark guard, and of course trying to get the gap right!
Anyway, turned over the engine and it started, tried revving it at different levels, and no misfiring. Satisfied, I took it for a trek around town to do some shopping and get some petrol. Touch wood she seems to be running fine - I just hope it stays that way!
I shall be able to say for certain by the end of the week - I do 60 miles of driving a day as part of my commute to work, so hopefully that will be a good test.
So its all looking good at the moment - touch wood it stays like that!

Thanks for all your help,

Marko

 

[alexGS]

Great stuff that you've got it running well.

When you have time you might like to borrow a timing light or find someone with one to check your timing, since the points gap is linked to the ignition timing (if the gap is smaller, the points open earlier). The timing for the 903 should, I think, be 10 degrees BTDC with the engine idling and the vacuum advance disconnected. I'm not sure if there are marks at the flywheel housing but if there are, I use them rather than the timing cover marks.

The points gap also needs to be checked for each lobe of the cam, or ideally use a dwell meter with engine running to ensure correct 55 degree dwell angle. With petrol prices the way they are, I think you want all the efficiency you can get!

That said, I guess you'll find it will be spot-on anyway, but I reckon it's worth a go with the timing light/dwell meter to be certain.

-Alex

 

[markoibook]

OK guys - have had the car running for a few days, and its certainly better than when it was broken down.
However, I have noticed (and I'm sure it may have done it before) that the engine sounds like its misfiring very slightly every so often, probably about every 10 seconds or so. As a result, there seems to some times be a slight loss of power - its hard to tell - I haven't driven it for two weeks, so maybe I'm being a bit picky.
Anyhow, it would be nice to get this resolved. So far the plugs,ht leads, coil lead, dissy cap, rotor arm, points and condensor have been changed in the last 3000 miles - the points and condensor most recently. I've played around with the points gap, but this doesn't seem to make much difference.
So anyone have any ideas?
It was misfiring a bit before all my problems, but i can't tell if its the same or worse now than it was. Maybe there is a common problem with the Uno that might be worth looking at? For example the small green cable that connects from the coil to the points had a dirty contact at the coil end, so I cleaned it all up - but didn't make much of a difference. Any ideas guys? The car seems to run ok, but it would be nice to get it going nice and smoothly. thanks for all the help to date!

Marko

 

[markoibook]

Any ideas peeps?

 

[SuperUno]

Probably the points have 'bedded' in and need re-checking to make sure the gap is correct. Also it really is worht checking the dwell angle as this is the real measurement that needs to be done. If you don't have the equipment/time etc... i'm sure as small garage will set-up them up for a tenner in their pocket.

 

[markoibook]

Ok yeah. I've tried readjusting the points a few days later, but didn't make much difference - maybe I should leave for a bit longer.
As for the dwell angle, I've read in the Haynes manual that with the magnetti marelli dissy they only way of adjusting the dwell angle is by adjusting the points gap - which seems a bit odd to me - surely thats no different to just adjusting the points gap!

 

[Chas Uno]

Ok yeah. I've tried readjusting the points a few days later, but didn't make much difference - maybe I should leave for a bit longer.
As for the dwell angle, I've read in the Haynes manual that with the magnetti marelli dissy they only way of adjusting the dwell angle is by adjusting the points gap - which seems a bit odd to me - surely thats no different to just adjusting the points gap!

Nope, the dwell angle is a kind of 'average' setting over all for lobes on the distributer shaft, not just on one lobe as when you set the gap with a feeler gauge.

You do still adjust the points to set the dwell angle, but you don't take any notice of the actual points gap. With a dwell meter connected you run the engine, then you increase or decrease the points gap until the require dwell setting is reached. You'll often find that with the correct dwell setting, the points gap is NOT the correct size as dwell often smoothes out wear in the distributor.

However, set to the correct dwell angle the distributor is now more accurate than just by setting the gap on one lobe with a feeler gauge.

Hope this makes sense!

 

[alexGS]

And also, some of the distributors allow you to adjust the points gap (dwell angle - they are one and the same adjustment as stated above) through a hole in the side of the distributor. This is much easier than having to take off the cap and rotor to shift the points each time!

I think that is where the Haynes manual confusion came from - they are saying that with the Magnetti Marelli distributor you can only adjust the dwell by repositioning the points.

However I think that there's a typo somewhere, as I personally think it's the Ducellier distributor that you can only adjust by repositioning the points... anyway whatever, you just need to find someone with a dwell meter now...

Thanks,
-Alex