1972 fiat 124 cranks has compression but won't start

[Itsbetterthannothin]

I am the new owner of a 1972 fiat 124 sport spider, I am planing on restoring this car to factory if possible but for now i would just like to get it started it cranks and when i put some gas in the carburetor it pops very rarely I was wondering if anyone would send some pictures of how you ignition system is wired so Ignition coil, ballast resistor, distributor, ect. Thanks for the help

[Budduncan]

If you put gas in the carb or a shot of starter fluid spray and it does not fire, it will be electrical. The ballast resistor will not matter, so you are left with battery (probably ok since it turns the starter), coil, points and condenser, wiring and voltage regulator. Open the distributor and check the rotor first, and have someone turn the entine over and see if the points are gapping. The points provide the changing field to the coil that kicks in the high voltage to the distributor. You could have a bad wire to the coil. The electircal is pretty simple and the parts are relatively inexpensive. Coils seldom fail, but they can. I would start with points and condensor, and maybe a new HT wire from the coil to the distributor. Check the wiring form the voltage regulator. The regulator can fail too, but if you are getting power to the coil then look to the High voltage wire to the distributor.

[Itsbetterthannothin]

Thanks we have checked the points they look fine we haven't replaced the condenser in the disputer but we are planning to, we found out the coil is bad so we bought a new one it was cheap but im wondering what wires go to were I've looked on the wiring diagram and there looks like there is only three wires going to the coil plus the one going to distributor but im not sure that this is right because I was told by the previous owner that there car was running exactly how it was, so i asked if he had some pictures of the engine bay and maybe how he wired the coil and surprisingly he did, I looked at them and there was a wire coming from the automatic choke and another condenser hooked to the negative side of the coil. Can some one just show me how to hook up the thing so i don't fry the coil. thanks

[Itsbetterthannothin]

Thanks we have checked the points they look fine we haven't replaced the condenser in the disputer but we are planning to, we found out the coil is bad so we bought a new one it was cheap but im wondering what wires go to were I've looked on the wiring diagram and there looks like there is only three wires going to the coil plus the one going to distributor but im not sure that this is right because I was told by the previous owner that there car was running exactly how it was, so i asked if he had some pictures of the engine bay and maybe how he wired the coil and surprisingly he did, I looked at them and there was a wire coming from the automatic choke and another condenser hooked to the negative side of the coil. Can some one just show me how to hook up the thing so i don't fry the coil. thanks

[spider2081]

The ignition points supply a momentary ground to the negative side of the coil. The ignition switch supplies battery voltage to the positive side of the coil. Have you checked for voltage on the positive side of the coil when the ignition switch is is both the "start" and "run" positions of the ignition switch.
Remove the wire connecting the points to the distributor at the coils negative terminal. Connect an ohm meter to the wire and the cars chassis. Put the car in 5th gear and slowly push the car so the engine is turning over. The meter should read zero ohms most of the time and then open or infinity for short periods of time. If the meter does not go to a value close to zero your points are most likely bad. If you don't have an ohm meter you can connect a test light between the coils positive terminal and the points wire removed from the coils negative terminal. On most Fiats this wire is black. the brown wire is for the tachometer.


Another check you can make: remove the coil wire from the distributor cap and place the bare end of the wire close to metal on the engine. With a separate wire momentarily ground the negative terminal of the coil. There should be a spark at the end of the coil wire to the metal on the engine if the coil is good and you have battery voltage on the positive side of the coil.

The capacitor is not necessary to start the car. If it were to fail in the shorted condition it could prevent the coil from working. You could disconnect the capacitor to see if the car starts with out damaging anything. The primary purpose of the capacitor is to reduce the points wear and pitting when the car is running.

[Itsbetterthannothin]

ok thank you again we replaced the points we checked for voltage at the positive side of the coil that is fine we ran that test pushing the car in fifth gear and the negative is also fine it still won't start i triple checked the wiring diagram every thing is right we removed the condenser from the negative side of the coil now we only have the external resistor the positive and negative we cranked it and nothing no spark from the coil i'm using this wiring diagram https://www.mirafiori.com/faq/content/6 ... MPLETE.pdf please explane which wires go to the negative side and which ones got to the positive thanks pictures of this car are coming soon

[spider2081]

Looking at the wire diagram from the Mirafiori link you posted:

B+ side of coil has a blue/black wire that comes from terminal 15 of the ignition switch. It should have battery voltage present when the key is in the "start or Run" positions.

The D or - side of the coil should have the wire that connects to the distributor points. Often this wire is black. Also there is a brown wire that connects to the tachometer. It is the signal for the tachometer. So the D terminal on the coil has 2 wires.

Not sure if I mentioned this test but if you disconnect the points wire from the "D" terminal of the coil and connect an ohm meter to it the meter should read close to 0 ohms when the points are closed and close to infinity when the points are opened. If it is open or closed all the time you will not have a spark.

I just saw an early spider with a rotor for a later model Spider in its distributor. The later model rotors have a resistor in them. I believe the rotors used with the distributors that have points do not have a resistor in the rotor. You should see a solid piece of brass across the top of the rotor.

[Itsbetterthannothin]

ok thank you for your help i'll try some more and see if it starts.

[Billholtzman]

Check timing. Try to move the distributor back and forth then, get a timing light hook it to wire 4 and time it to the crank.
Regards,
Bill

[Itsbetterthannothin]

Thanks bill we have adjusted the timing so we don't think that, thats the problem

[JohnMc]

I could be completely wrong but it sounds like you bought it without it running.
If that is the case, suggest you check timing just to see that you are not 180 degrees out. With the Fiat it just is not logical to me that when you set the timing you actually set it for park plug #4 if I recall correctly - and not #1.
Follow the manual just to ensure that it has been timed correctly. I got it wrong after rebuild and took about 1 hour to figure out what I did wrong.
If it ran before you ran it and have not changed out the belt please disregard.

[Itsbetterthannothin]

https://www.mirafiori.com/faq/content/6 ... MPLETE.pdf this is the wiring diagram i'm using it shows a blue and black wire going to the positive or B+ side of the coil, then a black wire and a brown one going to the negative side but im wondering what that thing on the D side of coil is its a box with a zig zaggy line through it does any one know what it is or if its even important?