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Old 26-10-2019   #1
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Strange Issue

Desperately need help here. I give up on this one and it's beyond my mechanical knowledge. Due to a backfiring issue, I heeded the advise of a few on this thread I started and I just changed a worn timing chain...

https://www.fiatforum.com/500-classi...g-issue-2.html

But now there is something different. I drove the car to a restaurant last night and when I went to go home, it would not start. I had to have it towed.
I have been asking Hobbler via email, but I can't keep bothering him with this so I'm going to everyone on here in hopes someone else has had this issue. When I pulled out spark plug number one (cylinder that is at the front of motor when looking at it through rear cover), the motor starts and runs on one cylinder. There is spark on cylinder one as I got shocked and I see the spark. When I put spark plug one back in, it won't start. I have a 123 ignition and just adjusted the tappets to the recommended clearance. I even changed the carb back to the original in hopes it was that and still nothing. The motor turns over but won't run so it's not the battery either. I give up at this point and I have no clue what the issue is. Any advice would be greatly appreciated.
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Old 27-10-2019   #2
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Re: Strange Issue

Quote Originally Posted by Labman View Post
When I pulled out spark plug number one (cylinder that is at the front of motor when looking at it through rear cover), the motor starts and runs on one cylinder. When I put spark plug one back in, it won't start.

That sounds like an insane problem.

Have you tried using new spark-plugs? It might be that the one cylinder firing on its own is struggling to overcome the compression on the "dead" cylinder when that one isn't igniting.

It could be down to several causes (as usual), but a faulty plug is easy to eliminate. You could even try swapping plugs, leaving cylinder 2 without a plug and seeing if it fires like that.

Working though the possibilities you might also have faulty HT leads etc, etc..........

You'll get there, but I do feel your pain...
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Last edited by fiat500; 27-10-2019 at 00:12.
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Old 27-10-2019   #3
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Re: Strange Issue

If it's any consolation I'm having a similar issue and I'm wondering if it's the 123. I cannot get my car to fire at all. Have spark and fuel but I suspect I'm not getting the spark at the correct time. I've come to the end of my limited talent so it'll be heading off to an expert soon. If I discover anything pertinent I'll let you know
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Old 27-10-2019   #4
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Re: Strange Issue

Now here is an interesting situation which 'Fayray' may just have high-lighted. About a year ago, my engine started running VERY badly; I had quite easily (and dare I say, fairly rapidly if not very rapidly in 1 or 2 places) done a 40 mile drive to visit some friends. The problem of the poor running started within about a mile of coming home, and persisted the whole way home. VERY poor running with mighty back-firing, often to the point the engine wouldn't run. If I let it cool down a bit, it would run fine for 4-5 miles, and then the problem would return. It was, to put it mildly, a somewhat stressful trip home!
The problem turned out to be the (very simple, Hall effect) electronic ignition. Due to where the distributor is located vis-a-vie the exit of the engine's'cooling' air, the distributors get very hot, so is it a case that the electronic ignition just plain gets fried? I fitted my spare ignition kit, and the engine fired up almost first pull and ran as sweet as ever.
I have tried to reduce the amount of air hot passing over the distributor, and more importantly, the ignition pack, by fitting a small extension INSIDE the cowling (by the distributor) so that when the thermostat is open, the air passing over the distributor is, to a greater or lesser amount, reduced. I have also moved the distributor round as far as possible to help the situation. The distributor still gets hot due to heat transfer from the crank-case, but I am hoping,not quite so hot as it did before. Only time will tell Has anybody else come up with this thought?
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Old 27-10-2019   #5
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Re: Strange Issue

Quote Originally Posted by fiat500 View Post
That sounds like an insane problem.

Have you tried using new spark-plugs? It might be that the one cylinder firing on its own is struggling to overcome the compression on the "dead" cylinder when that one isn't igniting.

It could be down to several causes (as usual), but a faulty plug is easy to eliminate. You could even try swapping plugs, leaving cylinder 2 without a plug and seeing if it fires like that.

Working though the possibilities you might also have faulty HT leads etc, etc..........

You'll get there, but I do feel your pain...


Thanks. First thing I did was change the plugs. And leaving cylinder two without a plug was tried too but it wouldnít start. So the issue is definitely with cylinder one.
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Old 27-10-2019   #6
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Re: Strange Issue

Quote Originally Posted by the hobbler View Post
Now here is an interesting situation which 'Fayray' may just have high-lighted. About a year ago, my engine started running VERY badly; I had quite easily (and dare I say, fairly rapidly if not very rapidly in 1 or 2 places) done a 40 mile drive to visit some friends. The problem of the poor running started within about a mile of coming home, and persisted the whole way home. VERY poor running with mighty back-firing, often to the point the engine wouldn't run. If I let it cool down a bit, it would run fine for 4-5 miles, and then the problem would return. It was, to put it mildly, a somewhat stressful trip home!

The problem turned out to be the (very simple, Hall effect) electronic ignition. Due to where the distributor is located vis-a-vie the exit of the engine's'cooling' air, the distributors get very hot, so is it a case that the electronic ignition just plain gets fried? I fitted my spare ignition kit, and the engine fired up almost first pull and ran as sweet as ever.

I have tried to reduce the amount of air hot passing over the distributor, and more importantly, the ignition pack, by fitting a small extension INSIDE the cowling (by the distributor) so that when the thermostat is open, the air passing over the distributor is, to a greater or lesser amount, reduced. I have also moved the distributor round as far as possible to help the situation. The distributor still gets hot due to heat transfer from the crank-case, but I am hoping,not quite so hot as it did before. Only time will tell Has anybody else come up with this thought?


When I bought the car four years ago, it came with a bunch of spare parts including a 123. Now itís not new and I can see it has been used. So I may swap it and see what happens but itís possible the spare had an issue as well and thatís why the previous owner bought a new one. I can only try.
Iím wondering how common it is for a 123 to fail and is it heat related over time?
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Old 27-10-2019   #7
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Re: Strange Issue

Do you have a conventional distributor that you could try? I don't think that engine heat would kill a 123 but out of range voltages are more likely to!
Even then, I had a faulty voltage regulator, so that over a few days or weeks I fried the battery;' 20,000 miles later the 123 is still thriving. They're rugged things.....and this is from someone who started as a doubter as regards the electronic conversion!.
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Old 27-10-2019   #8
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Re: Strange Issue

Quote Originally Posted by fiat500 View Post
Do you have a conventional distributor that you could try? I don't think that engine heat would kill a 123 but out of range voltages are more likely to!
Even then, I had a faulty voltage regulator, so that over a few days or weeks I fried the battery;' 20,000 miles later the 123 is still thriving. They're rugged things.....and this is from someone who started as a doubter as regards the electronic conversion!.


I have to look in the parts box. I might. I saw the original coil. Have to see if the cap, rotor and points are in there too.
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Old 27-10-2019   #9
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Re: Strange Issue

Is it definitely a 123 setup then. They have a custom distributor and you wouldn't be able to fit points etc. into it.
Quote Originally Posted by Labman View Post
I have to look in the parts box. I might. I saw the original coil. Have to see if the cap, rotor and points are in there too.
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Old 27-10-2019   #10
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Strange Issue

Quote Originally Posted by fiat500 View Post
Is it definitely a 123 setup then. They have a custom distributor and you wouldn't be able to fit points etc. into it.

Yes. I wish I had a working spare I could swap it with and see if this is the issue. The spare I have is dead.

Click image for larger version

Name:	59379285452__2C5D1A02-251A-4A4F-99B0-AB6F24B9A04C.JPG
Views:	24
Size:	478.6 KB
ID:	204091
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Last edited by Labman; 27-10-2019 at 19:15.
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Old 27-10-2019   #11
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Re: Strange Issue

Quote Originally Posted by Labman View Post
Yes. I wish I had a working spare I could swap it with and see if this is the issue. The spare I have is dead.

Attachment 204091

I hadn't thought of that; you have the version which does attach to the body of the existing distributor. I'm not familiar with how it does that but it does open out more interesting ways in which something got messed up. This may not necessarily be a fault inside the unit itself, but I wouldn't know where to start looking.....out of my depth with that one But it does offer the possibility of rebuilding using the original points and condenser as long as you still have all the removed internals.

Maybe a clue in these instructions...two magnets fitted over what I guess are the bob-weight pivots; is one missing or touching the circuit?

http://www.123ignition.nl/files/manu...al_FIAT500.pdf

I think it might also restrict the range of coil types that you can use, but not sure about that either.

I presume that you must have a coil with twin HT outputs?
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Last edited by fiat500; 27-10-2019 at 21:12.
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Old 27-10-2019   #12
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Re: Strange Issue

You are correct Peter---the "add-on" 123 electronic ignition comes with a pair of small tubular magnets which fit over the bob-weight posts, after you have stripped the points, base-plate and bob-weights out. And yes, you DO need a twin (wasted-spark) coil. Which brings us to another possible cause--is there a fault in the coil terminal to No1 spark plug. Being that sparks are sent to BOTH plugs at the same time (the one with the piston on its exhaust stroke therefore being 'wasted'), what would be the result if you swapped the ignition leads over at the PLUGS (but kept them in the same terminal at the coil)---I wonder if the fault would move to no2 plug? Just a thought!
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Old 27-10-2019   #13
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Re: Strange Issue

Apologies Peter, I forgot to mention that it is ONLY the "add-on" 123 ignition that requires a twin-coil, and this is the system Steven (Labman) has on his car. The 'complete distributor' unit has a rotor arm, so therefore you only need a 'normal' coil for that installation.
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Old 27-10-2019   #14
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Re: Strange Issue

Quote Originally Posted by the hobbler View Post
Apologies Peter, I forgot to mention that it is ONLY the "add-on" 123 ignition that requires a twin-coil, and this is the system Steven (Labman) has on his car. The 'complete distributor' unit has a rotor arm, so therefore you only need a 'normal' coil for that installation.
Thanks Tom, that part I was aware of; see above.

https://www.fiatforum.com/500-classi...ml#post4503356

I'm just pushing ideas around which might lead to a solution for Steven; rather than trying to cover the full technicalities of anything in particular. As I was indicating previously, my car has been running successfully on the 123 FIAT-2-R for more than 20,000 miles.
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Old 27-10-2019   #15
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Re: Strange Issue

there are I believe 3 types of 123 distributor types for teh 500/126 engine (excluding the usb new version)

1) the complete 123 Distributor with Distributor Cap
2) the Add on that sits on top of the std distributor
3) the 126 version that looks like the one in Labmans picture...
that is a complete distributor without a cap.

I know because I have 1 & 3
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