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MGB '76 MGB ignition trouble

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Too true, Roger. Good link.

That's a Luminition Hall Effect dizzy, a Lucas 45D. Best to replace its guts with a Pertronix unit.

As I posted in the earlier response, the Luminition system was first fitted in the '76 cars, to the best of my recollection. The control boxes were problematic. Even if the original Lucas parts were obtainable, a better solution is the newer, more robust Pertronix kit. and someone who understands how to fit the pieces and time the ignition after the change. Moss sells the conversion for just over $100, then someone with familiarity should be able to install it and get it going for at MOST two hours' time. It should take less, though. There's a client's '77 here now which I swapped out in less than 30 minutes.
 
I will definitely look I to upgrading to a pertronix and getting it fitted properly. In the meantime, I would like to double check all my Wiring between to coil and distributor... What wires should be getting power and when? Can I test with a bulb tester or do I need to check with my volt meter? I know the negative should flash my bulb tester when cranking engine and does not. Should my light on that negative be off or on when NOT cranking the engine? What other terminals or connections to e checked?
 
Whether or not your light will flash when connected to the negative terminal of your coil, with the engine cranking, will depend on what's happening in the distributor. Since that may be compromised, the question isn't answerable until your distributor is a known working unit.
 
With an electronic ignition, a test light usually won't flash as it would with points. A shop manual might have a simple test to determine if the electronic unit is working right. If not, be sure to check all the connections and especially check the distributor cap. Usually there is a carbon piece that contacts the center of the rotor--sometimes that breaks off. Do the same spark test with the high-voltage wire from the coil, not just the ones from the distributor cap, to see if it really is generating spark. If not, and the low-voltage connections look good, probably the electronic unit in the distributor has gone to that great Lucas home in the sky.

Also, get a shop manual, for sure, and study up on how these things work. If you don't have the basics, it's almost impossible to troubleshoot things properly.
 
Another couple of thoughts while I was out running around this morning--

1. That plastic piece on the right in your pictures is the sensor, which contains some or all of the electronics--I don't know if there is an external module too. It should be as close to the white ring as possible without it rubbing. There may be a spec for the clearance, but I suspect that's just to make sure it's close enough and not rubbing.

2. Since you have a spare distributor, you might try swapping out that sensor and seeing if that gets it working.

3. If it were me, I'd put in a Pertronix in any case. Much more reliable. Electronic components do deteriorate with heat and age, and of course the possibility of absorbed moisture and crud. And, back in the 70s, the electronic components that were cheap enough for automotive use were not very good, especially compared to today's.
 
Thank you for all of your responses and advice. I did not have anytime today to work on my B or do any research other than reading your posts. Hopefully I will be able to make some time tomorrow evening. Thank you again for all your help and advice.
 
Steve said:
Usually there is a carbon piece that contacts the center of the rotor--sometimes that breaks off. Do the same spark test with the high-voltage wire from the coil, not just the ones from the distributor cap, to see if it really is generating spark. If not, and the low-voltage connections look good, probably the electronic unit in the distributor has gone to that great Lucas home in the sky.
Click to expand...

If there's power at the + side if the coil, that's about all you need if the distributor components are also in operational order. If there's no spark at the plug wires, no spark at the center coil wire, the triggering device is FUBAR. Easy-peasy. Steve is correct. And if you get knocked on yer keester by the coil wire, that li'l carbon contact or the cap/rotor are the culprit.

There should be a white wire from the ignition switch to supply 12V to the plus side of the coil and a white/black one on the coil minus side going to the tach. With the Pertronix rig, you simply hook the red wire from the distributor unit to the positive on the coil and the black one to the negative side. Set the timing and drive.


EDIT: NAPA carries cap and rotor for the unit.
 
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Making progress?... I found the wire connection at the distributor was bad, wires breaking off at the copper connectors. So, after soldering them back together, the engine sounds much better when cranking. However, I still have no spark. The wires all seem dry and brittle, so I may still have an issue there somewhere. A new main harness is out of my price range at the moment, so I'll have to do what I can with it for now.

I am also thinking about that distributor... The electronic unit I lightly sanded the other day... I also sanded the edges of the rotor, could THAT be an issue as well?
 
If you're sanding the electronic pickup or reluctor, that's useless and potentially damaging. Sanding the brass leading edge and center contact point of the rotor would be of benefit. But again: NAPA carries cap and rotor for that unit. Specify for a 1977 to be certain you get a 45D cap (NAPA part numbers: EP61 & EP62, about $40 list price).

If you have 12V at the coil + side (solid white wire, from the ignition switch) and a good cap/rotor/plug wires and plugs it should get spark.

Did you check to see if the coil is getting trigger from the dizzy by pulling the coil wire from the center cap connection and (with a WELL insulated screwdriver or plastic pliers) see if it discharges by holding it close to a solid ground point?
 
I sanded those parts when I thought I had the points type distributor, thinking the partiI sanded was the points. I only did it lightly, only took me like 30 seconds so I do think believe that I damaged it but you all would know better than me.

I did check spark by pulling the coil wire from the center of the distributor against a couple different bolts on the engine. Not getting a spark at all.
 
Then it has to be the module or amplifier. Back to the Pertronix as the cure.
 
I have confirmed that the problem is with my distributor! I plugged in my spare and I got a great spark from my coil wire!
Now I need to learn how to adjust the timing if I change out the distributor...

I thought about just changing out the electronic unit, but I would need the remove the entire distributor to remove the wires anyway. So I might as well just replace the unit and readjust the timing. I hope you will be here for me still because I'm sure Iwill need your advice.
I
I do plan on upgradi ng to the pertronix, but for the time being, I'm going to go with what I have.
 
WOOHOO!

Nothing wrong with working with what you have at all. And we'll be here for your questions as you work through this. Ask away.
 
Nothing brings a smile like spark after days of working to get it... ask me how i know. Congrats.
 
So, I put in the other distributor, which I got a spark from out of the engine. And got nothing... Removed it again and tried it out of the engine e again.... Nothing. Think I have another bad wire in my harness again. I'll look at it again tomorrow...
 
Ok, I am lost again at my wits end. Been working on this thing for hours today. I cannot find any Wiring issues from the battery to the starter, coil and distributor. Everything appears to be in order with the diagram in the manuals. No loose connections found. I have tried both of my distributors in and out of the engine today and was able to get 1 weak spark on the same distributor that I got a great spark from just the other day. Again, this spark was with the distributor out of the car. But after numerous attempts, this was the 1 and only spark I was able to get today. Engine sounds strong, so I believe bad battery is not to blame. Any advice?
 
Joel --

If it were mine, I'd ditch the electronic distributor and swap in an early points type.
 
Matter of opinion with the electronic or points. I went tot a set of points when i first got my car and in the first few miles the electronic system died a twisted circuit board...ly death. Must of gotten warm and warped. I went with a points system from Jeff. I felt like it was costly when i was "pouring" money in to tires and my beat to **** wire wheels and a suspension bushing that imploded while i was leaning on the fender. His set up was plug and play and never failed until I burned the coil and points when I left the key on. From what it sounds like, if all your wires up to the coil are in order then try a dizzy that is in known working condition. On mine at least, the wiring is/was a mess beyond words. There are a lot of connections to steal your power. Or old corrupt wire.
It will work. These cars are old. It takes time, unfortunately money, patients, and love never hurt. If those wires are good and your positive sway the dizzy and coil and see what happens
 
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