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124 hello -- what about cold-start backfire!

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124 hello -- what about cold-start backfire!

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rsweibel

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Hello I'm Robert, a relatively new owner of a '78 124 spider in good condition. Looking forward to sharing photos later. This is my third Fiat but my first in 30+ years, having sworn them off in a fit after my X1/9 (my other high school sweetheart) burst into flames and perished.

I recently passed smog with all new vacuum hoses and a new Empi 32/36 carb with electric choke. Properly timed and nicely running for weeks, except... Just yesterday when I cold-started (Northern CA), the car's backfiring sounded like gunfire and didn't stop for five minutes. Sounded like it was coming from under the hood not from the tailpipe. Scary. Car ran great after that but I was afraid to go anywhere for fear of doing damage. Thoughts, anyone?
 
rsweibel said:
Hello I'm Robert, a relatively new owner of a '78 124 spider in good condition. Looking forward to sharing photos later. This is my third Fiat but my first in 30+ years, having sworn them off in a fit after my X1/9 (my other high school sweetheart) burst into flames and perished.

I recently passed smog with all new vacuum hoses and a new Empi 32/36 carb with electric choke. Properly timed and nicely running for weeks, except... Just yesterday when I cold-started (Northern CA), the car's backfiring sounded like gunfire and didn't stop for five minutes. Sounded like it was coming from under the hood not from the tailpipe. Scary. Car ran great after that but I was afraid to go anywhere for fear of doing damage. Thoughts, anyone?
Click to expand...



Hi Robert, and welcome,


firstly check the basics..
is the carburettor ( UK spelling) secure, are it's hoses and joints still intact,


then attempt to check the ignition timing hasn't slipped,
popping back through carb ; - ),


let us know what you find,
charlie
 
Hello and thanks! Everything is properly connected on my Empi. FYI I'm a beginner mechanic and I have no tools for timing but I suspect it's fine. I'm building skills and tools... So, I started it up yesterday and it didn't repeat the same behavior of scary non-stop backfiring during warm-up. It idled smoothly. When I revved the engine to 3k RPM -- pow! pow! pow! Yikes. As it warmed up further, it popped at 4k but otherwise stayed quiet. Had the hood open all this time and I honestly don't know if the sound came from the top of the engine or the tailpipe or both. Also, I don't believe my auto choke is working as the car won't hold a steady idle on cold start. Thoughts?
 
my thoughts reading through again this morning.. do you still have a distributor..( on the Ignition)

check the bob-weights work well, - advance / retard
and that the vacuum line ( if fitted) is working well,

that will mess-up your timing some..,

Charlie
 
Hello! I have a pretty new marelli distributor. Do you mean to say I need to remove the rotor and housing to get down to look the bob-weights? Below what's pictured in the photo?

What vaccuum line? Everything seems connected and tight.

Ran the car yesterday and it didn't want to idle for a while and finally it did but it sputtered and had no power. No backfires though.

I played with the idle mixture too but the screw only turned to the left and made the car run even more poorly.
 

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Hello! Who has time to work on cars? Days later... My plugs are fine, the distributor's fine, all the hoses seem fine. Timing is fine. Finally called my mechanic -- a Fiat / Alfa guy with a good reputation who I trust -- who told me it could have something to do with the "complicated" electric choke (on my new Empi carb) which hasn't worked right yet and I should just bring it in. So I dropped the car off. Sigh. I'll let you know what he says. Thanks for your advice.
 
Depending on ambient weather conditions in Northern CA, could you have condensation inside the distributor cap? or possibly a hairline crack?

If you can see a crack, scratch along it with a pointed metal object then paint it with nail varnish as a temporary repair.

If you can't see a crack, prop the cap up on top of the engine so you can see inside it (or hold the cap if you're brave), then in the dark, turn the engine over and look for sparks tracking inside the cap. Keep the cap away from any fuel source while turning the engine over.
.
 
Hello! The distributor is just fine. My mechanic played with the auto choke for an hour and he thinks the car will run better although admittedly I'm unsure of what he did. But he didn't charge me either since he'd seen the car just a few weeks ago. I'm planning on taking a drive up to Stinson CA this morning and you'll hear from me if I don't make it! Best, Robert
 
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