Technical Strange Issue

Labman · Oct 26, 2019

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-classic/475877-backfiring-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. :bang:

fiat500 · Oct 26, 2019

Labman said:
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...:bang:

Fayray · Oct 27, 2019

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

the hobbler · Oct 27, 2019

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?

Labman · Oct 27, 2019

fiat500 said:
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...:bang:

Thanks. First thing I did was change the plugs. And leaving cylinder two without a plug was tried too but it wouldn’t start. So the issue is definitely with cylinder one.

Labman · Oct 27, 2019

the hobbler said:
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 it’s not new and I can see it has been used. So I may swap it and see what happens but it’s possible the spare had an issue as well and that’s why the previous owner bought a new one. I can only try.
I’m wondering how common it is for a 123 to fail and is it heat related over time?

fiat500 · Oct 27, 2019

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!.

Labman · Oct 27, 2019

fiat500 said:
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.

fiat500 · Oct 27, 2019

Is it definitely a 123 setup then. They have a custom distributor and you wouldn't be able to fit points etc. into it.

Labman said:
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.

Labman · Oct 27, 2019

fiat500 said:
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.

fiat500 · Oct 27, 2019

Labman said:
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.

View 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:bang: 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/manuals/123manual_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?

the hobbler · Oct 27, 2019

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!

the hobbler · Oct 27, 2019

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.

fiat500 · Oct 27, 2019

the hobbler said:
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-classic/476795-strange-issue.html?p=4503356

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.

Bigvtwin996 · Oct 27, 2019

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

fiat500 · Oct 27, 2019

Bigvtwin996 said:
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

I see, two distributors fitted; playing safe, that will ensure that you're firing on all cylinders.

Labman · Oct 28, 2019

I’m going to get my hands on a compression tester and check out cylinder one to see if I have a blown head gasket. I can’t imagine this is the issue since I had the head done a couple of years ago and a new copper head gasket was installed. But you never know...

lazylobster · Oct 28, 2019

Silly question, did you swap the spark plug leads around as well as the spark plug?

Can't see a coil going but I would also swap the leads around on the coil too to ensure all good.

R

The Whitakers · Oct 28, 2019

I once had an issue (VW) that drove me insane!....I fitted new plugs, points, leads etc and the fault cleared but then came back...….turned out one of the new plugs was faulty too (Accuspark Plugs) and kept breaking down when hot so in went another set...…..all good now......

Labman · Oct 28, 2019

lazylobster said:
Silly question, did you swap the spark plug leads around as well as the spark plug?

Can't see a coil going but I would also swap the leads around on the coil too to ensure all good.

R

I did. I even changed the plugs.
I have a bad feeling the valve seat that was repaired a few years ago went bad again. A compression check will let me know for sure. If that's it, I'm not looking forward to doing that again. Big job.

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