MGB '76 MGB ignition trouble

[fireman91178]

I am getting no spark from my coil. test light is on at the positive side of coil. light is off at negative terminal of coil. light does not light up or flash on neg. terminal when I crank the engine. the coil gets warm. the resistor gets hot. If I disconnect any wire at or after the negative terminal, the test lamp lights up at neg. terminal. I have removed the cap from the distributor, and the rotor turns. I have tried 3 different coils (1 brand new), all act the same. I am baffled as to why I am getting no spark. Please help...
Thanks.

 

[DrEntropy]

Well, since you're from my ol' stompin' grounds (GOTL, actually) I'll toss out some thoughts...

Have you a points type distributor? If so, try running the S.O.'s emery board thru 'em a couple times and make sure they're gapped at 0.015" Try starting it again.

If you've got an electronic ignition (and ISRT that was the case originally; a "Luminition" Lucas unit), it was likely replaced with a Hall Effect aftermarket one, Pertronix comes to mind. You may have to replace it.

 

[DrEntropy]

Is the British parts place still open in Mentor?

 

[fireman91178]

I don't know of any place in Mentor for british car parts...I usually go through Moss for most of my parts.

I don't understand how the points play a roll in my lack of spark from the coil...the distributor is after the coil, so shouldn't the distributor need that spark in order to work in the first place?

 

[DrEntropy]

Ummm... the points set IN the distributor is the thing that sends the signal TO the coil to FIRE the spark. Then the distributor, well, distributes it to the appropriate cylinder.

Methinks you need to find a Bentley Press manual ("The Complete Official MGB" by title) for the car. They're on fleaBay or Moss has 'em.

We can try to assist but without more detail (distributor type, for starters) it's kinda hard to just guess what's going on. Has the car sat for any length of time?

 

[DrEntropy]

And welcome to the forum, BTW. You'll be hard-pressed to find a more willing and helpful place to learn about that car.

 

[fireman91178]

I have the Bentley and the Haynes manuals. I am just confused. I thoughtthe coil sends a spark the tthe distributor, then distributor sends that spark to the plugs...

I have an original type point to distributor as manufactured for a '76MGB.

If I take the coil wire from the distributor cap and place it near a grounded bolt as I turn the engine, shouldn't I get a spark?

I have filed the points... I think... Gonna try to start again...

 

[fireman91178]

No luck with a spark from the coil wire still. Test lamp is still not flashing at the negative terminal.

Thiscar has sat for about 10 months since it was last started. I was working on it alot a couple yearsago and rreceived lots of help from the forums at Mossmotors.com, today I found that forum does not exist anymore, thuswhy iIam here. I have mmade great strides on this vehicle in the past, I now find myself feeling like I have to start o er completely again from scratch.

Would the cold ohio weather have any effect on the trouble I am having today?

 

[Mickey Richaud]

Grounded out? That's always the first place I check. Be sure the insulator is in its proper place on the wiring post of the point set.

 

[fireman91178]

I'm not even sure if what I pulled out was the point to set... Pulled off the cap, plastic insert, rotor arm, then peice under rotor held in by 2 small ssteps attached to 2 wires by a soldered connection. This price had what appearsto be 3 tiny magnets which faced the rotor. These are what iI believe ed to be the points... Was I correct? I could not see how any more of the distributorwould come aapart without removing the entire unit.

 

[DrEntropy]

I'm not even sure if what I pulled out was the point to set...

THAT'S why I suggested the Bentley manual. A set of parts illustrations are in there, with WELL DEFINED explanations. I'd stop pulling stuff apart with abandon and try a systematic assessment of what is going on.

There are NO "THREE magnets" in any four cylinder engine I've ever seen, BTW.

I am baffled as to why I am getting no spark. Please help...
Thanks.

If we're to help, then we all need clear definitions of pieces-and-bits you're trying to identify by odd descriptors.

 

[DrEntropy]

I'm not even sure if what I pulled out was the point to set... Pulled off the cap, plastic insert, rotor arm, then peice under rotor held in by 2 small ssteps attached to 2 wires by a soldered connection. This price had what appearsto be 3 tiny magnets which faced the rotor. These are what iI believe ed to be the points... Was I correct? I could not see how any more of the distributorwould come aapart without removing the entire unit.

Can't quite be sure how to translate this. Take some photos of this unit and post 'em here.

 

[LarryK]

Doc is right, the distributor sends info to coil when to fire. Coil fires after distributor tells it to, then the firing of coil goes to cap which the distributor turns rotor and fires to the plug. Not just a coil or dis thing. Points are tuned to make the dis fire coil which starts process all over and over. If points are grounded or a wire rusted (oxidized) will hender process. Vehicle has set for some time check all wire connections to coil, points, and distributor. Since it is an electronic unit takes a little more troubleshooting. Give Doc the pics and he will lead you through the steps.

 

[fireman91178]

I have been looking at and using the parts pictures from the manuals and the Moss parts book. Still hard to tell what is what. I work 12 hour shifts the next 5 days, so not sure if I will get back to this issue before Friday or not. I will keep you guys posted and try to get some pics on here. I'm sure that with your help and knowledge, we can get this car running again. Thank you all!

 

[JPSmit]

welcome - and, no worries, you are at the right place - we'll get this going. I can't add a lot to this conversation, but, does a '76 'B still have points? By '76 my Midget had electronic ignition - which BTW is bullet proof.

 

[fireman91178]

I thought it was electric but according to the Moss catalog, it is points. Only shows 1 distributor for a '76 B.

 

[Mickey Richaud]

California B's had electronic; the rest of the country switched over to electronic in '77, I believe. Yours could've been switched, if not a California car.

Whatever the case, we can't be much help until you know what you've got. Points dizzies have "D" in the model number; electronics have "DE" or "DM".

 

[fireman91178]

the distributor that I have looks just like the one in the Moss catalog, which says it is points. These photos are of an older spare distributor from my car. I part in the 2nd photo I am pointing to with the marker is what I believed to be the points yesterday. I took this piece off and lightly sanded down the 3 nubs (which to me look like tiny magnets)which face the rotor. As I am typing this, I realize that I should have taken a picture of that piece where I sanded... Hopefully, these pictures will at least help clarify what type of distributor I have. If I need to get any other info for anyone or more pictures, please let me know.

 

[LarryK]

Looks electronic to me!

 

[Roger]

I don't know how to say this kindly, but it's pretty evident you're lost.
Those aren't points, and should not have been filed. It's hard to say whether you have done irreparable harm, but it is clear to me that you either need the hands-on help of a knowledgeable mechanic, or to study ignition systems in some detail.
Have a look here https://auto.howstuffworks.com/ignition-system4.htm