79 Bucking, Sputtering,Spitting ????????????

[seabeelt]

Fuel pressure is too low. You need at least 2.5, but 3 is better. I had a similar issue after installing my IDFs, turned out I had gunk in my fuel filter and enough of the very fine silty stuff was getting by and plugged one of the idle jets. I had a good solid 3 psi. So I took the top off the carb, cleaned all of the jets and associated tiny holes with carb cleaner and compressed air. Idle jet 2 was still plugged, so I took a small single strand of wire and ran it into the hole. Replaced the fuel filter. Problems solved. And now I have a steady 4 psi from my mechanical fuel pump.

[johnsje6]

My '79 with original carb does the same thing, but at random. Started surging badly yesterday on the way to work, barely made it to the parking lot, but when I went out at lunchtime to try to limp it home, it ran fine. Then it ran great all evening, this is the second time it has done this. I have cleaned the carb and jets, and have 5psi fuel pressure from an electric pump with the key on (not running), also pulled the fuel pickup and it looks clean. Car normally runs great (for a '79) but can't really trust it to get you where you are going. Is there a fuel pressure regulator on a carbureted '79? Or is the fuel pump itself the likely suspect? Or is 5 psi too much for the needle valve?

[JEEPER]

SO you can power thru the problem?? Then yes, it is not likely lack of fuel.

So next, what IS your fuel pressure?? These things need very little pressure.

Me, I'm one of those guys that think the factory knew what they were doing. I'm not fond of hang-on electirc pumps.

Still good news, sounds like it happens consistently. Not that familiar w a 79 carb, but I might be tempted to remove bowl vent line and see if it makes a diff.
Might remove vaccum advance line and see if it makes a diff.
Might hook up a timing light, arrange it so you can see flash from drivers seat, see if flash is nice and steady when issue happens.

I am borrowing back my timing light so I see if it flashes nice and steady(will post).

I have my timing light. Tomorrow I will see what happens with the electrical system and the fuel pressure. From all the advice I have received I'll see if the fuel pressure disappears when the car starts BUCKING. Everyone says that I should have 3 or 4 PSI so I am ordering a new fuel pump. I was looking at fuel pumps and there is an electric for a VW that only puts out 1 to 1 1/2 PSI, I wonder if that is what was installed in my car? I am leaving for ITALY on the 21st of this month(AUG) and returning the 23rd of OCT. so I need to try to do this before I leave or I'll have to continue this post next year.

[JEEPER]

Well Took a ride. First of all when I accelerate the fuel pressure goes to 0 (from 1 to 1 1/2) until I take my foot off the accelerator so when it bucks, sputters, and spits the fuel pressure gauge reads 0, as it does on acceleration. As far as the timing light it flashes through the problem so I'm guessing it is strictly fuel pressure. Fiat America directed the dealer to install the electric fuel pump so why it only puts out 1 1/2 PSI beats me. As soon as the fuel pump gets here and I install it I'll be back to report or look for other input.

[JEEPER]

majicwrench you called it. I just put the last hose on my new electric fuel pump and took it out for a spin and no matter how hard I stepped on it nothing NOT A BUCK, SPUTTER, or a SPIT. No matter how I tried to load it down nothing but smooth and plenty of power (for stock). My fuel pump pressure is now 4 to 4 1/2psi at idle before the fuel filter and when I really put my foot into it, it drops 3posi. It use to Idle at 1 or 1 1/2 at idle and drop to 0 during acceleration. I cant believe that I have tolerated this since the day in Sept of 1978 when I took delivery of it. Thank you everyone for your help.