electrical (I think)

My 72b died on me a while back and i've had a devil of a time figuring out why. On the side of the road, I checked for spark (not much else to do) and found that there was spark from the coil, though it looked weak, and absolutely no spark after the distributor. So after cursing myself for not keeping track of tuneup age, I ordered all parts and installed. The suprise came when there was absolutely no cange; then I remembered that the last full tune up occured about 3000 miles ago.
Next, of course was to replace the coil, even though it was only about a year old. I picked up Bosch's Blue coil (just in case anyone is familiar with it) and actually drove for 15 miles before standing on the side of the road waiting for a tow again- half a mile from the house, even.

Anyway, it seems to me to be electrical which I know nothing about. Is there anyone who would be willing to teach me? I know its a big thing I'm asking, but I've already learned the hard way that the local shops are less than trustworthy with this car...

edothas,
Just a couple of questions that might help narrow this down. When you turn the key on, does the red light on the dash next to the high beams light, does this light come on? Also, do you know that the fuel pump is working for sure? I do not know how much you know, so I do not want to insult your intelegence, I am just trying to narrow things down a little bit and help you out. I know that at least on my car, when I first turn the key on I can hear the fuel pump pumping until it builds pressure. If you do not hear the fuel pump, I can tell you how to check it before you replace it. Tonight when I go home, I will check my wire schematics and see if there is anything that could short that could cause you to get spark from the coil, but not from the distributer. Do you have points, or electronic ignition? Anyway, just trying to help you narrow things down a little.
You are wanting to learn about electrical. On MGBs, a lot of time some of the problems are simply bad connections. Before changing out a component, make sure that it is getting power to it before you change it out. A lot of wiring can be done with a simple test light. Also, the Robert Bentley MGB shop repair manuals have excellent wiring diagrams in them. They are labeled with the color of each wire and name of each component. They seem kind of impossing sometimes. But make several copies of the diagram of your car, and then highlight the wire that you are looking for with a highlighter. This makes it easier to see where it goes, what it does, and what is conects to. A continuity tester can come it real hany to sometimes. Both these tools can be bought at your local Sears or parts store fairly cheaply. If you have more questions, just ask, and I will see what I can do to help.

Check Terminal Lead And Condensor Hookup On Points Post.the Plastic Piece On Top Has To Go Through Those 2 Connections. The Connectors Can't Touch The Post Only The Spring.put Test Light On Terminal Lead On Outside Of Dist. Turn Engine It Should Blink.THEN CHECK SPARK FROM COILTO DIST THEN FROM DISTRIBUTER TO PLUGS ...MGBSS63

Thanks for the replies. And don't worry about insulting my intelligence- I'm dumb as a rock!

I have checked the fuel pump, it works. I've also had the dash apart making sure there's not an intermitent short there; everything checks out. I suppose I might mention that I have had problems with the tach reading 0 rpm for an instant while driving, usually when shifting.

I got curious and checked the plug wires- the coil-to-distributor wire reads about 50 ohms, and the cap-to-plug wires read about 40,000 ohms. This last one seems a bit high to me.... I also checked the same (40k ohm) wire while connected to the plug and could get no reading whatsoever. I'm not Nicola Tesla, but this seems like it might be the problem? What kind of resistance should I expect from plug wires and plugs? I wish this car had a neck... These are, by the way, shiny-new AC Delco wires and Bosch Platinum plugs, so I'm hesitant to pronounce them bad.
Hope this narrows things a little.

Thanks for the replies. And don't worry about insulting my intelligence- I'm dumb as a rock!

I have checked the fuel pump, it works. I've also had the dash apart making sure there's not an intermitent short there; everything checks out. I suppose I might mention that I have had problems with the tach reading 0 rpm for an instant while driving, usually when shifting.

I got curious and checked the plug wires- the coil-to-distributor wire reads about 50 ohms, and the cap-to-plug wires read about 40,000 ohms. This last one seems a bit high to me.... I also checked the same (40k ohm) wire while connected to the plug and could get no reading whatsoever. I'm not Nicola Tesla, but this seems like it might be the problem? What kind of resistance should I expect from plug wires and plugs? I wish this car had a neck... These are, by the way, shiny-new AC Delco wires and Bosch Platinum plugs, so I'm hesitant to pronounce them bad.
Hope this narrows things a little.
1ST CHECK IF POINTS ARE WORKING CONNECT TEST LIGHT TO POST ON THE OUTSIDE OF DISTRIBUTER. IT SHOULD BLINK WHEN YOU TRY TO START CAR IF IT DOESN'T LOOK INTO MY OTHER RESPONSE.MGBSS63

40 k resistance does sound a little high for plug wires. I just checked mine and get around 6 k, 7.5 mm silicone Autolite wires. Yours shouldn't be high enough to keep the car from running. I also checked a wire with a plug and plug adds about 5 k ohms to the wire resistance, NGK resistor type plugs. You may have some type of film or coating on the plugs that keeps yur meter from reading, I had to probe pretty hard to get a reading. You did check the plug at the center electrode?

Reviewing what you have said it seems your car normally will run for awhile and then decides to stop. Is this assumption correct? You also stated your tach dies sometines, usually when you shift. That would indicate the ignition is also dying intermittently, however I cannot relate that to shifting other than perhaps lower idle speed. With that information I would assume the points, plugs and high tension wires are ok. Do you have a timing light? If you do when the engine dies connect the timing light to any plug wire and crank the engine over. If the timing light flashes you are getting spark through the plug wire. No fire at plug, try the timing light at the distributor to coil high tension wire. If no spark there go back to the low tension circuit. A word about new parts, sometimes they fail. Lucas rotors sometimes fail in a very short time. If you have no spark at the plugs but it's ok at the coil, try replacing the rotor.

Clifton

I checked the points & condenser circuit, its definitely good. That would have been a nice fix... Also, I looked at the resistance on the wires and plugs again & it seems that I got it wrong the first go-round by a factor of 10...

In the process of searching, I also found mention of worn distributors; it seems that the most reliable sign is a dusting of metal inside the cap. Is there such a thing as a distributor so worn that a new cap and rotor will not *temporarily* allieviate the problem?
(sigh) If MGs weren't so beautiful, I'd sell right now...

Do you still have spark from coil to cap?Did you try a test light either on the outside of dist or the negative side of coil to see if light will blink when you turn engine?How many volts do you have on the positive side of coil?What kind of wire and cap doyou have ,the push on spark plug wires or the screw in from underneath the cap style?With the cap off can you verify that rotor is actually turning?If you have spark to the dist. but not out(a crisp blue spark)then something happened to your new cap and rotor.If you don't have crisp spark to dist and your totally sure contact points are gapped correctly and you get the blinking light I keep telling you about then there must be something wrong with your bosche coil groundig out or not right voltage to it .mgbss63

One more thing or bad coil wire.mgbss63