Technical No spark troubleshooting help, please!

[tatsuru]

I read some similar threads regarding no spark but I still can't figure out what's wrong with my 1972 Fiat 500L... Need help!
I'm relatively new to classic Fiat and I haven't done much troubleshooting like this.

The car died suddenly a few weeks ago and now the engine cranks but not starting.
I'm not getting any spark at the spark plugs, so that seems to be the root cause. (Used spark plug tester from Amazon)

So far, I replaced...

- Ignition coil
- Distributor breaker arm and adjusted the gap
- Distributor cap is relatively new (replaced 6 months ago?)
- Capacitor (condenser) that is attached to the distributor (found broken wire)
- Fuel pump, carburetor with new one. (I see fuel in the floating chamber.)

And so far I checked...

- Spark plug cables continuity seem to be all good
- Getting 12.5V at the battery terminals
- Getting 10.5V at the ignition coil terminals (is that normal?)
- Coil resistivity is 2- 3 ohms on both new and old coil
- Seems to be getting fuel into the carburetor
- Engine cranks fine
- Distributor contact point is opening & closing
- No blown fuse

What do you all experts suggest I should check next?
I'm sure it's something stupid that I completely missed...

Appreciate your help!

 

[Toshi 975]

You could check that you do not have a dead short circuit at the distributor. With the distributor cap off and ignition on if you open the points manually with the end of a small screwdriver you should see a spark at the points. Also it is not unknown for new condensers to be faulty.

 

[fiat500]

I read some similar threads regarding no spark but I still can't figure out what's wrong with my 1972 Fiat 500L... Need help!
I'm relatively new to classic Fiat and I haven't done much troubleshooting like this.

The car died suddenly a few weeks ago and now the engine cranks but not starting.
I'm not getting any spark at the spark plugs, so that seems to be the root cause. (Used spark plug tester from Amazon)

So far, I replaced...

- Ignition coil
- Distributor breaker arm and adjusted the gap
- Distributor cap is relatively new (replaced 6 months ago?)
- Capacitor (condenser) that is attached to the distributor (found broken wire)
- Fuel pump, carburetor with new one. (I see fuel in the floating chamber.)

And so far I checked...

- Spark plug cables continuity seem to be all good
- Getting 12.5V at the battery terminals
- Getting 10.5V at the ignition coil terminals (is that normal?)
- Coil resistivity is 2- 3 ohms on both new and old coil
- Seems to be getting fuel into the carburetor
- Engine cranks fine
- Distributor contact point is opening & closing
- No blown fuse

What do you all experts suggest I should check next?
I'm sure it's something stupid that I completely missed...

Appreciate your help!

You should have full battery voltage at the coil + terminal. Maybe charge the battery first; if it's still 10.5v, there may be a problem with dirty contacts or terminals, eg. inside the ignition switch. You might want to make a temporary, separate connection to the coil from the battery or try another battery.
The ignition coil should measure 3 ohms across the LT terminals.
Check that the moving part of the points is properly insulated from the base; once found a set where the pivot bush was inexplicably made from metal rather than insulating mica. Also, check that the insulation on the LT terminal on the side of the distributor has not failed; the wire from the coil should only make contact with the spring-steel of the points. Check that the LT cable is connected to the correct terminal on the coil; it doesn't always follow that a new one has the same orientation of terminals.
It will be a simple fault when you find it.....good luck.

 

[tatsuru]

You could check that you do not have a dead short circuit at the distributor. With the distributor cap off and ignition on if you open the points manually with the end of a small screwdriver you should see a spark at the points. Also it is not unknown for new condensers to be faulty.

I think you were spot on! I took out the point contacts and the breaker arm, cleaned up the insulators, etc. And she started up just like nothing ever happened! Thanks for your advise, very much appreciated!!

 

[tatsuru]

You should have full battery voltage at the coil + terminal. Maybe charge the battery first; if it's still 10.5v, there may be a problem with dirty contacts or terminals, eg. inside the ignition switch. You might want to make a temporary, separate connection to the coil from the battery or try another battery.
The ignition coil should measure 3 ohms across the LT terminals.
Check that the moving part of the points is properly insulated from the base; once found a set where the pivot bush was inexplicably made from metal rather than insulating mica. Also, check that the insulation on the LT terminal on the side of the distributor has not failed; the wire from the coil should only make contact with the spring-steel of the points. Check that the LT cable is connected to the correct terminal on the coil; it doesn't always follow that a new one has the same orientation of terminals.
It will be a simple fault when you find it.....good luck.

Thanks for your detailed advise! It looks like the problem was a bad insulation between the points and the base as you mentioned. I don't know exactly where the problem was. But as soon as I partially disassembled the distributor and put it back together, she started right up. So happy to be able to drive her again! Thanks again for your advise and encouragement!!