1975 Spider only runs with choke

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kendall
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1975 Spider only runs with choke

Post by kendall » Sat Jul 06, 2019 8:02 pm

Hello everyone,

I just bought a 1975 124 spider and it will only run when the choke is closed, either when the engine is cold or when the choke in the dash is pulled.

The car had been sitting for about a year before this and was claimed to be running when it was parked (what else is there to say). From what I can tell it does have the 32 ADFA carb this year came with, though I can't find any markings on it.

So far I have done the following:

1. remove the sending fuel hose from the carb and check the flow from the pump into a bottle. It seems to be generous, more than enough to fill the float bowl.
2. removed the top choke section of the carb and cleaned the float bowl, which did have much sediment in it, and removed and cleaned the jets. I also sprayed out the emulsion tubes, idle jet on the side, and idle adjusting screw. From what I can tell these areas are all clear from blockages.
3. I determined the choke is working, as I can feel the spring tension on the dash throttle when the engine temp comes up.

The engine will run around 2000 rpm and higher and not die. There have been a few times where it idled around 1000 rpm but it was quite rough and died in about 30 seconds.

It is likely the gas in the tank is old, but would old gas be enough to cause the engine to die when trying to idle?

I'm not sure where to look other than rebuilding and remounting the whole carb. At least that way it will be working correctly. I understand that there could be a vacuum leak somewhere else, but where would be the best place to start looking, and how would I go about doing it when the engine just wants to die?

If anyone has some suggestions on what to check I would greatly appreciate it.

It has a hardtop and everything. I hope this isn't one of those "life lessons" my dad told me about.

Thanks in advance.
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18Fiatsandcounting
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Re: 1975 Spider only runs with choke

Post by 18Fiatsandcounting » Sat Jul 06, 2019 8:52 pm

From your description, it sounds to me like the idle circuit isn't working, and based on the sediment you found in the float bowl, the idle orifices and passageways could be partially (or fully) plugged up. I suggest taking apart the carburetor and giving it a good cleaning, and checking to make sure that all passageways are clear.

A couple things:
1. You probably know this, but the choke does 2 things: it richens the mixture and it raises the idle speed. The raising of the idle speed is probably what is keeping the car running when the choke is pulled.
2. Make doubly sure that the idle jet (the one mounted in the holder in the side of the carb) and the idle mixture screw (the one at the base of the carb) are really clean. I think you already did this, but I mention it only because I had a Fiat that wouldn't idle but ran fine otherwise, and it turned out to be a very tiny speck of something blocking the orifice in the end of the idle jet.

-Bryan
kendall
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Re: 1975 Spider only runs with choke

Post by kendall » Sat Jul 06, 2019 9:08 pm

Thank you for the reply Bryan.

I will double check the idle jet and screw. I was just reading this (http://www.njfiats.org/joomla/images/st ... rkbook.pdf) and noticed the idle solenoid mentioned. I have not checked that solenoid. It says that if it does not see power the idle will not be open. This is the solenoid in question:

https://autoricambi.us/collections/fuel ... oid-197578

I thought it was related to a high idle setting when I was looking at the carb earlier today. I will check it to make sure there's power to the lead and that the solenoid works.

I will update with more info.
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bartigue
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Re: 1975 Spider only runs with choke

Post by bartigue » Sat Jul 06, 2019 11:05 pm

The idle solenoid and fast idle are not related to each other, though they act upon the same circuit. Don't confuse them in diagnosis.

With the ignition ON but the engine OFF unplug the idle solenoid and test it for 12V. If it has power then tap it against its connector on the solenoid. It should audibly click. If not, it's likely gone bad or needs a good cleaning. This solenoid controls all fuel delivery below about 2000 RPM.

The fast idle control, if it all works, keeps the throttle partially open during deceleration from 3rd and 4th gear, and is activated by three switches, one at the clutch and two in the transmission. It's a relic of bad emissions control laws and I would block it off before diagnosing my carburetor, just to be certain it isn't the problem or isn't making the problem worse.
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Brad Artigue
1969, 1969, 1970, 1979, 1980, 1981, 1982, and 1982 124 Spiders
1969, 1970 850 Spiders
77 X1/9
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fiatfactory
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Re: 1975 Spider only runs with choke

Post by fiatfactory » Sun Jul 07, 2019 8:02 am

+1 with Brad on the idle stop solenoid being stuck /faulty / blocked ... simple fix and likely the issue.

SteveC
kendall
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Re: 1975 Spider only runs with choke

Post by kendall » Sun Jul 07, 2019 1:32 pm

Thanks for the replies.

I checked the idle solenoid yesterday. The jet was clogged and the solenoid is not working. Luckily there is power showing up to the connector for it so I don't have to chase an electrical issue. I ordered a new one along with a shop manual and wiring diagrams. I double checked the idle jet on the other side as well.

It will now idle and not die. It is running around 1000 rpm. What is the recommended idle speed for the 1800 engine? The idle isn't completely smooth right now, is there something else I can check?

It will buck and die when I put the car into gear. I will admit I don't have experience with manual cars. Do I need to gas it to keep it alive when I shift from being parked? Or is there something else I need to check? Of course I'm parked on a slight incline because that's where it was easiest to stop it before.
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bartigue
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Re: 1975 Spider only runs with choke

Post by bartigue » Sun Jul 07, 2019 2:21 pm

Proper idle speed is 850 RPM, +/- 50 RPM, so 800-900 and you're good.

If you are not applying some power to the gas when in 1st gear, from a stop, then the car will buck. Getting used to a manual on an incline is a real pain in the ass; try to get it somewhere flat, like a big parking lot, and practice from stop. As the clutch is disengaging press the gas to increase engine speed. You'll get it quickly.
-----------------------------------------------------------
Brad Artigue
1969, 1969, 1970, 1979, 1980, 1981, 1982, and 1982 124 Spiders
1969, 1970 850 Spiders
77 X1/9
http://fiat.artigue.com
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18Fiatsandcounting
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Re: 1975 Spider only runs with choke

Post by 18Fiatsandcounting » Sun Jul 07, 2019 2:27 pm

I was just about to respond pretty much exactly as Brad did, but he beat me to it. I'll just add that the lack of a smooth idle has many potential causes, from the simple (adjusting the idle mixture screw at the base of the carburetor or correcting the ignition timing) to more complex causes such as an air leak into the intake system or an emission control device that's not acting as it should. There are other causes, but I'd start with the idle mixture screw and checking the timing.

-Bryan
kendall
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Re: 1975 Spider only runs with choke

Post by kendall » Mon Jul 08, 2019 1:20 am

Thanks again for the help.

I've garaged the car for the week because of a work trip. I'll have to adjust the carb when I get back. I did some other work on it today and let it idle for a while and for the most part it ran fine. It did die once when I was moving to the garage but that may have been me.

What is the consensus on air cleaners like these ones? https://autoricambi.us/products/air-cle ... val-197580

Are they high performance in that they allow more flow? I could be wrong, but isn't the filtering element going to be much smaller?

The original air cleaner on my car is pretty ratty. Some of the posts for attaching the lid are striped or loose. It also seems two of the holes to attach the air cleaner to the top of the carb are stripped. I suppose the solution is a nut, bolt, and lock washer?
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friedman
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Re: 1975 Spider only runs with choke

Post by friedman » Mon Jul 08, 2019 8:39 am

In theory these types of filters flow more air but your stock filter probably flows all the air you engine can use. I like small sport filters because they provide easier access to the carb.
Carl in Virginia
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