Carb / intake problem

[sdh]

I have a 77 spider with a 34ADF carb.
Will not idle smoothly or for long before stalling. Occasionally bucks while driving and stalls when I let off the gas.
Yesterday the egr pipe to the manifold fell off (rust) so I bent the pipe over and have a good seal (I think). The car never did idle properly before this. Idle solenoid clicks when I unplug it. Electrovalves have been bypassed sometime in the past.
I am not well versed on fixing carbs but there are no Fiat guys around here. Any suggestions?

Steve in Winnipeg

[manoa matt]

Since its a 77 do you still have the dual points distributor? Before diagnosing any carb problem you first need to make sure your ignition system is working flawlessly. Make sure the points gap, dwell, and timing are properly set. Also try replacing the condensers if they are in doubt.

You are sure its the 34ADF and not the stock 32ADFA? You may need to adjust the air/fuel ratio a bit to suit your motor. Vacuum leaks on the intake side (carb, hoses, or manifold) will cause the car to idle high. Leaks on the exhaust side will sometimes cause the car to idle low.

I have a factory manual for the 32ADFA carb that explains its workings and provides the adjustment specs, I can't say if they would be the same, but they should be pretty close for the 34ADF. Send me and email and I can send you the files.

matt.scarton@gmail.com

[sptcoupe]

The 34 ADF was used on a lot of applications, so check the jets and note what they are. I have seen a number of these of on FIATS that were jetted way too rich. I have also cured a number of rough running ADFs by going to an electrical fuel pump with the pressure set a 4.5 lbs. For some reason, the mechanical FIAT pump seems to be too weak for these carbs at idle and just off idle.

The advice above is spot on, too. Clean up the basics first (igniiton, leaks), then look at the fuel supply and jets.

[racydave]

Ive heard of some carbs getting loose. Grab the fuel iine and the carb and see if itll move around.

[sdh]

I tightened everything I could find, made sure there were no leaks. The car will now idle but it is around 1500 rpm, lower than that it stalls out. Adjusting the idle mixture has no effect.
Is this a float problem?
Thanks Matt for the diagrams.

Steve

[manoa matt]

Re-check and re-set the timing. You said idle solenoid clicks when you unplug it. It should be the other way around. Turn the car and electric off. Unplug the connection from the idle solenoid. Turn the key to the on position but do not start the car. Touch the connection to the idle solenoid. Every time you touch it, it should click.

[sdh]

Thats what I meant re the solenoid so I guess it is working. I don't have a timing light so I will get one asap.

[majicwrench]

This is NOT a float problem UNLESS you can see huge quantities of fuel spilling into throttle bores when it stalls. It is NOT a fuel pump issue, lack of fuel would show up at speed, under load, NOT at idle, when the engine only uses a tiny amount of fuel. This is NOT a timing issue, if the car runs OK at speed the timing is close enough to make it idle. This is NOT a problem with the jets, unless you have gone in and changed them around. Has the car idled poorly since you've had it?? Or has it idled well at some point??
Get idle as low as you can, then slowly put your hand over the carb, or slightly shut the choke. Did the idle pick up?? If so, it is running to lean, and the idle circuit is likely plugged.
The first thing I would do it clear out the ilde circuit. They plug often. Pull idle mixture screw, pull idle soleniod now blow compressed air, or carb cleaner with the little tube ( you have your safety glasses on, right?) thru the holes, of course while the engine is off and cool. Put idle mixture screw back in, then about 2 turns out, see if it works.
Keith

[sdh]

I cleaned out the idle and the car will now idle but it is quite rough at anything under 1200 rpm. Went for a ride and at city speeds with very little throttle there is an occasional slight hesitation. Any ideas what to do next.

Steve

[majicwrench]

Once again, cup your hand over the carb and slowly restrict the airflow while it is idling rough. Does is smooth out?? If so it is still too lean.
Does the idle mix screw now change the idle as it is turned in or out?
Keith