1971 MGB GT - Trip to British Motor Museum - not 56k friendly - see page 39

[Matty]

32 minutes ago, Rustybullethole said:

Or for slightly more than an hours work chuck it all in the bin and fit an mx5 lump or the like. 

Blasphemy.  Burn him 

[Peter C]

4 hours ago, Barry Cade said:

This bit

I’m sure that the points make correct contact with the cam but I will double check when I fit the new parts.

[Peter C]

3 hours ago, artdjones said:

Do the point contacts look burned? When the ignition is on with the points closed and they are then flicked open with the end of a screwdriver is there noticeable sparking across the point contacts. 

That's what the condenser is for - to stop arcing across the points when the contact is made or broken. If a condenser isn't working the signs of arcing are easily seen and tested for. Even if the condenser only starts breaking down after the engine has been running for a while, the point burning will still be there.

If it is the condenser, the idea above of using a modern one separately mounted seems the best idea to me.

The old points looked ok and the first replacement points were only fitted for a couple of days and look like new.

[chadders]

The MGB lump is fine.

Personally I'd get a 123, mine has been flawless over the 12+ years that I've had it.

[busmansholiday]

The capacitor connection circled in yellow, is that actually making a good contact,?

[Peter C]

10 hours ago, busmansholiday said:

The capacitor connection circled in yellow, is that actually making a good contact,?

I think so, the nut keeps the cables together.

[scdan4]

That black wire looks knackered and may have internal problems to go with the visible insulation breaks. If it's the low tension power feed then I'd be replacing it to make sure it's not going high resistance / intermittent when 'vibing'

 

[Peter C]

30 minutes ago, scdan4 said:

That black wire looks knackered and may have internal problems to go with the visible insulation breaks. If it's the low tension power feed then I'd be replacing it to make sure it's not going high resistance / intermittent when 'vibing'

 

Agreed.

Later today I will remove the distributor, check everything over, replace the black cable and go for another test drive.

[Bmwdumptruck]

12 hours ago, busmansholiday said:

The capacitor connection circled in yellow, is that actually making a good contact,?

Shouldn’t the spade on the capacitor wire be under the nut rather than the insulation? Long long time since I’ve played with any points so I’m probably wrong, but it doesn’t look quite right to me!! 

[Peter C]

First thing I did today was check the wiring to the coil, as suggested by @SiC

According to: https://www.mgexp.com/forum/mgb-and-gt-forum.1/ignition-coil-wiring.3342026/ the white wire should extend to the + terminal on the coil. Mine were fixed wrong way round so I've swapped them over.

On previous occasions, I've been tinkering with the distributor whilst it was in situ, doing my back in and at times not really seeing what I was doing.

Today, I loosened the distributor clamp and pulled the distributor out. It took less than a minute. I have marked up the distributor and clamp so that I know how to put it back in.

With the distributor clamped in a vice, with good lighting, heat and music, working on the distributor was much easier and almost fun.

Based on a previously presented photo, @Barry Cade pointed out that the heel of the points was not making contact with the cam.

He was right.

I loosened the points and adjusted them to get the heel as close to the cam as possible. Even then the heel was not touching the cam.

With the points adjusted like this, the points gap was massive, way too wide.

@Barry Cade I presume there is nothing that can be done, when the points are shut, the heel will not be touching the cam.

The earthing wire appears to be rivetted to the base plate.

Rather than disturbing the cable, which didn't feel brittle at all, I put some additional insulation around it.

As for this cable.

This much of it remains active.

I have exchanged emails with Matt from the Distributor Doctor. Hitherto, he has quoted:

The correct fibre heel points are £14.50, rotor arm £8.95, condenser £8.95 and distributor cap £19.50 plus postage and VAT, so £68.88 all in.

I have asked Matt to quote for a new coil and today I emailed him again asking for the replacement cable. I suspect the total cost will be more than the Accuspark kit but hopefully the ignition system will finally be sorted.

More soon.

[SiC]

I personally have actually got on better with the one piece points that are made of plastic. They all close up a bit after wearing in a little. 

What condition were the points contacts in?

[Peter C]

22 minutes ago, SiC said:

I personally have actually got on better with the one piece points that are made of plastic. They all close up a bit after wearing in a little. 

What condition were the points contacts in?

All ok I think, no evidence of any deterioration.

[SiC]

Suggests condenser wasn't the cause of issues last time. I'd keep a keen ear that the pump is ticking regularly as it should when running. 

[Peter C]

7 minutes ago, SiC said:

Suggests condenser wasn't the cause of issues last time. I'd keep a keen ear that the pump is ticking regularly as it should when running. 

Definitely does. The pump must have been replaced recently, it looks brand new.

[SiC]

Doesn't stop electrical issues to the pump. Bullet connections in the engine bay and earth attachment on the rear bumper bolts are where to check. If earth goes or plays up, fuel gauge reads wrong, sinks or empty as same connection. 

 I ran an additional earth from the pump to the neg battery as easy access. 

[Peter C]

20 hours ago, busmansholiday said:

The capacitor connection circled in yellow, is that actually making a good contact,?

This looks useful.

[plasticvandan]

The fibre heeled points are a definite win,modern repros are made of a soft plastic that wears too fast. I grabbed a bag of old tufnol heeled ones for my minor years ago and they were great. As to he heel not touching the cam,I don't see why it would if the pointy part of the cam isn't touching it,as surely you adjust the points to open at the right gap when it's on the "widest" part of the cam. They usually had a felt wiper to soak in oil to rub against the cam as well.

 

[lesapandre]

Yes. I think whether it's touching or not is irrelevant as that is the point of the spin at which the points are closed - the open gap is set at the widest point of the cam - ie the pointy bit - hence it opens and closes.

These distributors can wear and cause problems ie the cam bearings, weights or vacuum advance etc.?

[Peter C]

2 hours ago, lesapandre said:

These distributors can wear and cause problems ie the cam bearings, weights or vacuum advance etc.?

This!

The cam has a bit of play but is silent when rotated.

I sucked on the vacuum advance pipe as hard as I could and the mechanism inside the distributor moved by a couple of millimetres. I assume there should have been a more significant reaction?

Thing is, even with these faults, last time I drove the MGB, the engine ran ok for quite a while, then, all of a sudden, it started to struggle and splutter. 

I’ve read up on how coils fail and most posts suggest that they either work ok or not at all, whilst others state that a duff coil will cause the sort of symptoms that I’m experiencing. Not sure whether the incorrectly connected terminals have caused the condition of the coil to deteriorate. Either way, I will be replacing the coil together with the other bits that I’ve ordered from DD.

[Matty]

58 minutes ago, Peter C said:

This!

The cam has a bit of play but is silent when rotated.

I sucked on the vacuum advance pipe as hard as I could and the mechanism inside the distributor moved by a couple of millimetres. I assume there should have been a more significant reaction?

Thing is, even with these faults, last time I drove the MGB, the engine ran ok for quite a while, then, all of a sudden, it started to struggle and splutter. 

I’ve read up on how coils fail and most posts suggest that they either work ok or not at all, whilst others state that a duff coil will cause the sort of symptoms that I’m experiencing. Not sure whether the incorrectly connected terminals have caused the condition of the coil to deteriorate. Either way, I will be replacing the coil together with the other bits that I’ve ordered from DD.

Literally don't understand electickery but I'm pretty sure that it's perfectly plausible that a coil in the first stages of terminal decline could break down under load/heat then present as working when cool again. 

If you want to set your mind at rest, replace the ignition parts one at a time until you can't get the same symptoms after a drive. Ultimately it's a fuck about and from the photo's the whole lot needs doing anyway. But sometimes it's nice to know.

[mat_the_cat]

3 minutes ago, Matty said:

I'm pretty sure that it's perfectly plausible that a coil in the first stages of terminal decline could break down under load/heat then present as working when cool again. 

It's perfectly possible, and also partially dependent on conditions within the combustion chamber, i.e engine speed and load. The high voltage will find the easiest path to earth, whether that be via the spark plugs as intended, or shorting out internally within a failing coil.

As an amusing aside, I used to have an old BMW motorbike on which the coil had started to fail, and would happen more often when hot and accelerating hard. One of the first times the fault manifested itself was whilst filtering through stationary traffic up to a red light. With unusually good luck the lights changed to green just as I approached, so I opened the throttle wide to get ahead of the cars before they all started moving. I started to accelerate, and then the engine completely cut out. Only for half a second or so, but this was enough to pull in a great dollop of unburnt fuel into the exhaust, which promptly ignited with a huge backfire as the engine fired again. At this point it was probably doing around 5k rpm with the throttle fully open. The resultant sudden surge of power made me pull an inadvertant wheelie, and after I had somehow managed to control the tankslapper and land it sucessfully, I pulled ahead of the cars before immediately pulling into a side road to recollect myself.

[Peter C]

Parcelforce are due to deliver a package from the Distributor Doctor tomorrow, containing a new coil, cap, rotor arm, points, condenser and the low voltage cable.

Including p&p and VAT, these bits have set me back £182. Not cheap but worth it if they solve the problem.

[plasticvandan]

Re your vac advance sucking,that sounds about right,you should be able to see it move a few mm,when you get good at it you can slide your tongue over the pipe and see if it holds position. A light grease on the bob weight pivots will help keep everything flying out as it should.you can experiment with different strength springs for different characteristics but it's a bit of a dark art.

It's all good fun to play with and a good way to learn how the things work.csn confirm if you get the position of the nylon spacers wrong you loose all spark lol

[High Jetter]

3 hours ago, plasticvandan said:

mm,when you get good at it you can slide your tongue over the pipe and see if it holds position. 

I know exactly what you mean, but could be misconstrued 😀

[colino]

Lots of old cars will run fine with points like that, as long as they ramp up on the cam properly.  The condenser and or coil can run fine for a while until they get hot, then they break down, with coils, sometimes noticeably warm to the touch.  I'd replace the condenser first, then the points then the coil.  If you just blast the parts cannon, you won't know what the failure point really was.

[juular]

On 01/02/2025 at 22:48, Matty said:

Literally don't understand electickery but I'm pretty sure that it's perfectly plausible that a coil in the first stages of terminal decline could break down under load/heat then present as working when cool again. 

This is exactly what happened with @MrsJuular's Toledo.  It would run absolutely fine for around 15-20 minutes and then start to misfire before cutting out completely.  Part of the problem was that it was a lower voltage coil that was supposed to be ballasted, but someone had removed the ballast resistor so it was getting 14V instead of the 9V it was designed for, and as a result was overheating/failing much quicker.

[Zelandeth]

Leaving the ignition on can also result in the coil failing rather spectacularly rather than just silently burning out.  I made that mistake once (Metro I think), and the thing went off like a bloody shotgun and launched the innards out of the can.  Not sure which went further - the bits of coil or me jumping.  Suffice to say it scared the crap out of me and made sure I never made that mistake again.

[Dj_efk]

@Peter Chow come you elected to spend the money on the existing setup - as opposed to a 123 upgrade?

I hate points and condenser with a passion so my two routes have always been either Accuspark kit or 123 in order to rid myself of them and simplify maintenance schedules.

[Peter C]

@juular I am aware that there are different types of ignition coils and I had no idea whether the coil that was fitted to my MG was correct.

@Zelandeth I am aware of the damage that leaving the ignition on can do to the ignition system. I always switch the ignition off whenever I can. I am sure that having the positive and negative cables wrong way round didn't help much either.

@Dj_efk I got a lot of advice from a Facebook MG group, who advised that good quality original parts are the way to go. The cost of the 123 upgrade also put me off.

The new bits arrived today. 

The reason for the higher than expected invoice is the ignition coil, which cost £69.95 plus VAT. 

I fitted the new bits inside the distributor.

All looked good.

I fitted the new cap, all good, the distributor was ready to go.

I re-fitted the distributor, aligned the timing marks and re-connected the vacuum advance pipe.

I fitted the new coil and bracket. The white cable goes on the positive terminal, the black and white cable goes on the negative terminal. I got this information from the internet and from an MGB handbook that was kindly donated to me by @Mr Pastry.

Everything looked good.

Went to start the engine. Nothing. Had no spark.

I checked all the connections and tried again. Nothing. Had no spark.

I removed the distributor, put it back in the vice, checked the points gap, all connections and tried again. Nothing. Had no spark.

I removed the distributor again, put it back in the vice, removed all the new bits, checked them over, refitted everything and tried again. Nothing. Had no spark. 

I disconnected the new coil and reconnected the old one and tried again. Nothing. Had no spark.

I reconnected the new coil.

I removed the distributor again, put it back in the vice, removed all the new bits and refitted the old ones and tried again. The engine fired up straight away.

I then begun a long and boring process of replacing the old bits with the new ones, one by one, starting with the rotor arm, then the low voltage cable, then the condenser and finally the points. With all new bits back on, the engine fired up straight away. HOW???? WHY???? WHAT THE FUCK WAS WRONG BEFORE????

I took the MG for a 2 mile drive up and down between Loudwater and Beaconsfield and the engine ran fine. Weather conditions (rain), imminent darkness, a build up of evening traffic and an urgent need to do respond to work emails prevented me from driving further today.

Remember last time I drove the MG, it ran fine for the first half an hour, then started to splutter etc. Time and weather permitting, I will take it out for a longer drive tomorrow.

More soon.

[Zelandeth]

Dicky ignition switch or fuse in line (no idea if applicable) making the power supply temperamental?