Need help troubleshooting ignition

[BrandonBJ8]

After taking apart my generator to make sure everything looked good, I started my car and it ran for about 10-20 seconds and then died. I haven't been able to get it to start since. I thought I had an issue with my wires, so I replaced the cap and wires.

- I'm getting fuel at the carbs and everything there looks good.
- The coil is producing a spark.
- I'm now not getting a spark at the plugs when I test.

I have Petronix ignition. See picture.

Any ideas on how I can start troubleshooting this to figure out what is wrong?

Thanks!

 

[Billm]

Your rotor looks OK but maybe you should try another one- also look in the cap to see if the carbon piece is still there and properly sprung.
BillM
-also look to see if your wire from the coil to the cap is good (hold the wire up to the block and see if it sparks)

 

[BrandonBJ8]

I'm getting no spark when I hold the red wire from the coil to the cap up to the block.

When I test voltage across the coil, I don't get a reading with the ground on the - terminal. If I place the ground of the tester on a ground somewhere else on the car, I get 12.3v. Could the lack of ground at the coil be causing it? How can I check that?

Thanks!

 

[57_BN4]

When I test voltage across the coil, I don't get a reading with the ground on the - terminal. If I place the ground of the tester on a ground somewhere else on the car, I get 12.3v.

Rotate the engine slowly, you should get voltage 'across' the coil only when the transistor is conducting which is only at certain points around the cycle. If you don't get any change there is a possibility your Pertroinx just gave up.

Check there is good continuity between the pertronix mounting plate and the -ve battery and also that the air gap between the pertronix and the rotor isn't too big.

Andy.

 

[BrandonBJ8]

I rotated the engine using the fan and didn't notice a change. But I'm not getting a reading at all when connected to the - terminal of the coil. With my testing lamp, when I turn the key with the lamp connected to the + and - terminals of the coil, it came on for a split second and then went out. I think something is off with the coil's ground.

Regrading your second comment, what's the -ve battery?

Rotate the engine slowly, you should get voltage 'across' the coil only when the transistor is conducting which is only at certain points around the cycle. If you don't get any change there is a possibility your Pertroinx just gave up.

Check there is good continuity between the pertronix mounting plate and the -ve battery and also that the air gap between the pertronix and the rotor isn't too big.

Andy.

 

[Deleted member 8987]

And, if you leave the key on for any length of time, you fry Pertronix as a general rule.

 

[57_BN4]

Sorry, I mean the negative terminal of the battery. The Pertronix baseplate should have good continuity (near zero ohms) between it and the battery negative, on a negative earth car.

Is your pertronix wired with its red wire to coil +, black wire to coil -?

If you have a test light, it should glow on/off as the engine is rotated on the fan when connected across the + and - of the coil. The coil is grounded to the distributor body through an electronic switch inside the Pertronix but only at certain places around the cycle. Don't leave your key turned on for long with the bulb on (current flowing) as this can overheat the Pertronix.

Andy.

 

[BrandonBJ8]

The petronix is wired with the red to the + and the black to the -.

The test light turned on and off as I cranked the ignition so that seems to be correct.

What else can I check? It must be something with the ignition/distributor.

 

[57_BN4]

change your coil, not that much else it could be. Pull off one of the + or - coil wires then check the resistance across the + and - terminals. Should be about 3 ohms. Open circuit = duff coil.

 

[Deleted member 8987]

Yet, your initial post said you had spark out of the coil....but now you don't?

 

[BrandonBJ8]

I do have spark out of the coil. I have a spare coil that I changed out and get the same result so I don't think the issue is the coil.

It's gotta be something with the Petronix. Any thoughts?

 

[tahoe healey]

Try putting the points back. May tell you a lot.

 

[Johnny]

If you have a spare replace the condenser.

You did say you don't have spark at the plugs, right?

The pertronix, like points, just interrupt the spark not providing it, the coil does that. I'd still check the plug wires. You might also pull a spark plug and connect it to the wire and lay the plug on ground so you can see the plug fire.

 

[57_BN4]

hmmm. Can't be pertronix, thats working fine. Must be the rotor/cap/leads then if you have spark at the coil.

 

[BrandonBJ8]

So I just tested two plugs and am getting a spark at the plugs now. The first spark upon cranking the engine is much brighter than the subsequent ones if that makes a difference.

 

[Billm]

Here is a Pertronix troubleshooting sheet from Jeff:
BillM

You can look at it without downloading here:
https://www.mgexperience.net/phorum/read.php?3,1909211

 

[Healey_Z]

So I just tested two plugs and am getting a spark at the plugs now. The first spark upon cranking the engine is much brighter than the subsequent ones if that makes a difference.

If you swap wires, does the good spark follow the wire? If you swap the plugs, does it follow the plug?