77 Fiat Starts then Stalls when given throttle

[m3mackenzie]

Hi Guys,

Hoping someone on here can point me in the right direction. I purchased a 77 spider at the end of summer. It seemed to run fine both times I went to view the car. The exhaust was open at the downpipe as the temporary tubing between the down pipe and the muffler had rusted through. Other then being loud, the car ran well on the test drive. It was a little finicky at idle and would occasionally stall at stops. For the price of the car ($2,000), i figured it was a good enough deal even if it had some problems and purchased it. I drove the car about 40 miles home (mostly highway) and other than the occasional backfire/missfire, it handled the drive fine. I got it home, parked it, and ordered a center muffler off AutoRicambi. The previous owner had purchased an Ansa muffler at some point, so I attached the center muffler with clamps and called that good. I also changed the in-line fuel filter just below the carb.

The only other issue i have worked on was attaching the airbox to the carb properly. When i took the top off the airbox, i discovered that only 1 bolt was holding it to the carb, the other three were missing. I went to the hardware store and purchased the appropriate bolts and installed them.

Since i had parked it, i had not had time to start or drive the car. After fixing the exhaust and replacing the fuel filter and missing bolts, I started the car and had a decent idle going. I let the car idle for about 5 minutes without any input on my part. Unfortunately, as soon as I attempted to apply any throttle (either by peddle or by the knob), the car dies. I am able to then restart the car without serious issue, but the idle is rougher and i am still not able to apply any throttle.

After a few times, i end up giving up because i do not want to toast the starter or kill the battery. This has happened on two occasions separated by a few weeks (due to my schedule, i have not had a lot of time to mess with it). Each time it seems to start and idle fine the first time, but each time it stalls, the successive idle is worse.

Does anyone have any thoughts on what direction i should start working first?

Thank you,
Mike

[GeorgeT]

I haven't had a carbed car in a while but my recollection is that a worn out accelerator pump can cause this. Also, is the float in the carb correctly adjusted?

[Rambo]

Make sure your getting solid fuel pressure at the carb inlet as a weak fuel pump could cause this. If your getting fuel my bet is on the carb. A clean and rebuild (replacing most carb components), and adjustment should be a good start.

[131]

I haven't had a carbed car in a while but my recollection is that a worn out accelerator pump can cause this. Also, is the float in the carb correctly adjusted?

My first stop would be the accelerator pump diaphragm. With the engine off, looking down the carby throat, as you move the throttle is there a good squirt of fuel added, if not, check the pump diaphragm. If there is, check float level, needle and seat, and fuel supply.

[m3mackenzie]

Thank you, guys. I appreciate the suggestions. I will have a look at the carb and probably order a carb rebuild.

Mike

[carl]

Just as a general rule of thumb, anytime I buy a Fiat I give it a nice general tuneup no matter what the previous owner says they did. More so if the car has sat for a long time. Check the points/cap/rotor, check the ignition timing (set at 10 degrees at idle, not the factory mandated 0 degrees), clean out the carb and all it's parts. If the car sat, odds are there is a lot of water in the gas. Check that the cams are timed correctly and plan on a timing belt change and valve adjustment. Previous owners can be well intentioned but totally incompetent with maintenance. Oh yea, change the oil and filter.

carl