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1977 MG Midget 1500 no spark...

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Mojan Mojan Norouzi
Fremont, CA, USA   USA
Hi,
My recommendation is always below three test:
Let us know the result.






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Mojan Mojan Norouzi
Fremont, CA, USA   USA
Yes, you are 100% right, good point.

In reply to # 3515379 by jmac cursichella,
You asked if the neg. side of coil should be grounded in your first post. The answer is no, not by running a wire from the neg. to the body of the car. The neg side of the coil is grounded through the distributor and your points. The coil is a type of capacitor. When the points are closed the coil collects and builds voltage. When the points open that voltage is released by the coil giving you a powerful spark. If you ground the coil directly to the body the coil will build voltage but will not release the charge properly when the points open.
It has been a while since I dealt with points. I got this right didn't I Dick?

cursichella Charles M
St Helena, CA, USA   USA
In reply to # 3515322 by dickmoritz You say your battery is at 12.6 volts, which is nearly fully charged. Did you confirm that you also have 12.6 volts at coil + ? Do you have another coil that you can try this same test on? You should be getting a healthy blue spark...

Dick



In reply to # 3515095 by cursichella Hi,

Ok, first tests tested ok. Next, I tested for the spark from the coil that goes to the distributor cap with spark plug on ground. I got a spark but it was weak and didn't spark with each try. Maybe 1 out of 5 tries gave off a very tiny blue spark.

By the way, battery is at 12.6v.
Tested again. Battery had 12.5 volts and + terminal on coil had 12.4 volts. After testing the coil wire for spark like before, which had same results, both battery and coil + terminal had 12.3 volts.

I do have a spare coil but it's the one that I replaced with the current one. The old coil gave weird readings on the multimeter at the time and replacing it initially fixed prior ignition problems.

I'll try the test methods in the moss videos later today. Will post results

In reply to # 3515379 by jmac cursichella,
You asked if the neg. side of coil should be grounded in your first post. The answer is no, not by running a wire from the neg. to the body of the car. The neg side of the coil is grounded through the distributor and your points. The coil is a type of capacitor. When the points are closed the coil collects and builds voltage. When the points open that voltage is released by the coil giving you a powerful spark. If you ground the coil directly to the body the coil will build voltage but will not release the charge properly when the points open.
It has been a while since I dealt with points. I got this right didn't I Dick?

Oh okay that makes sense, thanks for the explanation!



Edited 5 time(s). Last edit at 2017-05-20 11:50 AM by cursichella.

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dickmoritz Avatar
dickmoritz Gold Member Dick Moritz
Philly 'burbs, PA, USA   USA
Jere,

You're exactly right, including your description of how the coil works. Many folks don't realize that it's when the primary circuit is broken when the points open is when the coil fires its high tension spark.

You'll note in a previous post that I had suggested removing all wires from the coil - terminal and using a jumper wire to alternator make and break a ground connection from the negative side of the coil. The purpose for doing so is to replicate the action of the points closing and opening, simulating what happens inside the distributor. If manually making and breaking the ground circuit produces a good spark at the temporary spark plug setup, then we know that the coil is capable or producing a suitable spark, and the problem must lie elsewhere...

Dick

In reply to # 3515379 by jmac cursichella,
You asked if the neg. side of coil should be grounded in your first post. The answer is no, not by running a wire from the neg. to the body of the car. The neg side of the coil is grounded through the distributor and your points. The coil is a type of capacitor. When the points are closed the coil collects and builds voltage. When the points open that voltage is released by the coil giving you a powerful spark. If you ground the coil directly to the body the coil will build voltage but will not release the charge properly when the points open.
It has been a while since I dealt with points. I got this right didn't I Dick?



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

cursichella Charles M
St Helena, CA, USA   USA
So that would mean the coil is incapable of producing a powerful spark based on the results that I got? Odd because it's practically brand new!



Edited 2 time(s). Last edit at 2017-05-20 01:45 PM by cursichella.

cursichella Charles M
St Helena, CA, USA   USA
I've had to work all this weekend so I won't be able to dive back in to this until tomorrow.

In the meantime, thank you all for your suggestions. Yesterday I used my lunch break to go to buy a new coil and condenser but Napa was closed when I got there at 1. :/

Thank you, thank you!

ODC427R tim carter
Boksburg, Gauteng, South Africa   ZAF
1983 MG MGF "Sredni Vastar VI"
I once pulled the engine out of a beetle trying to fix a misfire when all I needed to do was change the condenser! We all have to learn smiling smiley, just change it, they're not expensive. tim

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Havenor Avatar
Havenor Richard Costa
Fairhaven, MA, USA   USA
I'm no expert on diagnosing these things but I do recall from the old days that the rule of thumb was always replace the condenser with the points. In every tune up it was standard practice.

cursichella Charles M
St Helena, CA, USA   USA
Hi Dick and all,

I've replaced the coil and condenser. I retested using the steps you outlined.

All passed until I removed the cardboard. No spark at the points.

It looks like there may betoo much of a gap in between the points but I don't have a gap measuring tool. Does it sound like they should be adjusted? Here's a photo.

By the way, thank you for your patience! smiling smiley))



Edited 1 time(s). Last edit at 2017-05-25 09:24 PM by cursichella.

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66jalopy Avatar
66jalopy Silver Member Phillip Jolliffe
Lake City, FL, USA   USA
Use an old razor blade, it will get you close.

Mojan Mojan Norouzi
Fremont, CA, USA   USA
You need filler gauge. Watch below video on how to set points:

dickmoritz Avatar
dickmoritz Gold Member Dick Moritz
Philly 'burbs, PA, USA   USA
Spec for point gap on most British cars is 0.015, which is about the thickness of a match book cover, if you're old enough to remember cardboard match books... cool smiley

But note that the gap should be when the points are open their widest, as evidenced by the rubbing block of the movable contact being on the highest point of one of the four lobes on the distributor shaft cam. Suggest you also note that the points are fully closed when the rubbing block is on the low point of the cam.

If the gap is about right, and if you're sure the points are closing all the way, next step would be to have a helper crank the engine while you observe the points. You should see a spark across the points each time they open...

Dick

In reply to # 3519113 by cursichella Hi Dick and all,

I've replaced the coil and condenser. I retested using the steps you outlined.

All passed until I removed the cardboard. No spark at the points.

It looks like there may betoo much of a gap in between the points but I don't have a gap measuring tool. Does it sound like they should be adjusted? Here's a photo.

By the way, thank you for your patience! smiling smiley))



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

cursichella Charles M
St Helena, CA, USA   USA
Hiiiii,

Ok I've set the points .019 and both are sparking but and opening at the same time. Engine tried to fire even while testing the 4th spark plug. Put plug back in and tried to fire but won't. I made a sound recording because it makes a distinct sound but I'm unable to upload an mp3 file.

Best way to describe it would be it makes the normal repeating sound a car makes when trying to start then it switches to one long (versus repeating) higher pitched whirring sound that makes me impulsively want to turn it off (and try again).

66jalopy Avatar
66jalopy Silver Member Phillip Jolliffe
Lake City, FL, USA   USA
It's firing and kicking the starter out. Are you sure you have correct firing order? Advance it a couple degrees and try again.

cursichella Charles M
St Helena, CA, USA   USA
Thank you for your reply. I've checked and the four plugs are firing and in the correct order.

This is my first time dealing with points, etc., so forgive me for but could you explain what you mean by "Advance it a couple degrees"? Thanks!

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