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Speaking of No Spark

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ronzet

ronzet

Jedi Knight
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LBC Fans...

I have been driving my freshly restored MGA around for a while working out the bugs as they come up. I adjusted my valves this weekend (not related to the problem) and fired it off. It ran well for about five minutes, started missing and then quit. Fuel is pumping (fuel IS in the tank) but, as I troubleshot, found not a spark to the plugs.

I checked the feed (12v) to the coil and checked for spark as I open the points... all fine.

I then replaced the coil with one from my 'on the hard' '66 B.. still no joy.

I then replaced the distributor along with wires and cap in my A with the assembly from my B just to check for spark... still no joy.. fuse is still intact...

This is a VERY simple circuit... Before I pull the rest of my hair out... AM I MISSING SOMETHING???

I am all ears... /bcforum/images/%%GRAEMLIN_URL%%/wall.gif
 
Steve,

Nice to hear from you. I hope all is well.

Yes, the B ran fine when last I ran it a few months ago...I did not fire it off before pulling the parts this weekend.
 
Have you checked that your points are actually opening when the engine cranks?
Bill
 
Billm,

Yep, cranked the little guy over, watched it open and close, checked the gap when it wasn't moving and in the open position... 'tis driving me nuts..
 
Steve,

Yep.. With the switch on, I can open the points and see a small spark as the points open capacitor discharges.. Once...

I think that you are supposed to see that discharge...??
 
Yeah, that doesn't convince me that all is good up to that point though. Make sure the coil is wired properly and check for a short to ground in the system. I dunno, it has me stumped but something in the back of my mind finds this very familiar.
 
Steve,
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]it has me stumped but something in the back of my mind finds this very familiar [/QUOTE]

I agree. Keep in mind that it ran very well and then didn't. I suspect that something let go.

The other variable is the questionable 'replacement' parts that I have substituted... troubleshooting with unknowns causes unknowns... /bcforum/images/%%GRAEMLIN_URL%%/rolleyes.gif

Thanks for your comments.
 
Have you hooked a spark plug directly to the coil (hi-tension lead) to see if it is a cap/rotor question?
Bill
 
Every scenario I'd suggest doesn't make sense since you say you swapped the entire ignition system (sans coil) from the B to the A. You did swap caps and rotors? Inside both dizzys did you look for the ground wire between the breaker plate and the dizzy housing (and confirm it's intact)? You said the points gap was set. Was it set on both dizzys? Very unlikely... but with the cap removed the rotor does spin while you crank the engine doesn't it?
 
That's my confusion. He's replaced every piece of the puzzle except the plugs, but no spark TO the plugs anyway. The second dizzy is supposedly functional although we can't be sure unless the other car will run with it installed. Assuming the second dizzy is good, something else is going on.

I wish you were closer so we could install a known good dizzy in the car.
 
Gentlemen,

Thanks for all of the suggestions...

Since I have an unknown in the replacement dizzy (the one from my B) I think that I will re-install the dizzy (and related components) back into my B and fire it off. I need to re-intall the fuel pump on the B but other than that it will be a two hour job. Once the B runs I will have a known good dizzy to use while troubleshooting the A....

Film at 11:00...
 
Stewart - I'm new to MGB's here, having just paurchased a '77.

I LOVE the treatment on the nose of your 75! Looks like a blend of both rubber bumper and chrome bumper. Can I accomplish this on my '77 more easily than a complete chrome bumper conversion?

Mike
 
I think it's easier but I've never done a cb conversion. Basically you have to cut off the front bumper mounts flush with the body. Notch the upper frame rail to fit the grill and fill in the turn signal holes in the front fenders then cut out for the lights. The bumper then bolts on the front valance.
 
Well it looks great. Better than chrome bumper to me. I read through your restoration thread on the car and learned a lot. Thanks!
 
Gentlemen,

Thanks for your comments... Just to finish this out.. I ended up replacing all of the ignition wires and the rotor. once done it fired right up. I had ohmed out all of the leads on the cap and found ALL OF THEM open?!?!? I have ordered a new coil anyway...

Thanks again.. now just waiting for the next bug to come to the surface...
 
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