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Tuning New to me rough 1772 Fiat 850, won't run continuously

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Tuning New to me rough 1772 Fiat 850, won't run continuously

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DavidHallbuzz

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It will fire and rev up, then dies. The mechanical fuel pump has been bypassed by an electrical one; I'm wondering if that's the issue?
 
From my experience, there may well be a problem with either blocked jet, and/or the float in the reservoir chamber, isn't working properly and stopping the fuel getting through. Have you checked the quality of fuel in the tank? I had the same issue, until I flushed the old fuel out and introduced new, clean and decent quality fuel.
 
So, I sort of got it going. The mechanical fuel pump leaks, the electric one seems sufficient. I pumped out the old gas; it was very yellow. But, new gas is yellow too. I'm guessing that's iron oxide?
Anyway, I determined the choke and cable was stuck. I oiled everything and loosened it all up. I got it running, but only at a fast idle at full choke (choke is on 1 barrel of 2). I drove it around; it ran very poorly and then got worse. It would start, rev up and stall. I got it home on full choke.

I think I'll have t0 dismantle and clean the carb next.

Lately I took off all of the wheels, had the rotten tires removed and have sanded, wire brushed all 4. They were rusty and even pitted in places. The tires would only hold air for a couple hours,
 
Hi, I would say, it sounds like you may well have some detritus in the carb jets, fuel lines and perhaps, float inlet valve. I can hear your frustration and resignation, I have been there. If you can take the carb off, literally, used compressed air, blow out all of the fuel ways, nozzles, jets and change the internal filtre for a start. if the tank was or is rusted, this won't help matters as even a micro particle, will potentially, clog up the carb jet(s). In addition, check carefully for air leaks, especially around the base, the gaskets can, if not tightened down correctly or isn't sitting on the manifold flat, can (will) draw in unwanted air, which will make starting, running and performing, a pain!
 
Messiahbrand said:
Hi, I would say, it sounds like you may well have some detritus in the carb jets, fuel lines and perhaps, float inlet valve. I can hear your frustration and resignation, I have been there. If you can take the carb off, literally, used compressed air, blow out all of the fuel ways, nozzles, jets and change the internal filtre for a start. if the tank was or is rusted, this won't help matters as even a micro particle, will potentially, clog up the carb jet(s). In addition, check carefully for air leaks, especially around the base, the gaskets can, if not tightened down correctly or isn't sitting on the manifold flat, can (will) draw in unwanted air, which will make starting, running and performing, a pain!
Click to expand...

Maybe rig up a temporary tank.. from a mower..etc


Get it running well on the clean fuel.. then try the old tank again

Limit the doubts :)
 
Thank you everyone; great ideas here. Decades ago I dealt with lots of old cars, but somehow never a rusty tank. It's been a long time since I've worked on something so old. I'm going to try just about everything mentioned. I wonder if a weed-whacker tank would work, gravity fed for testing?

I also bought some:
"STAR BRITE Star Tron Fuel Tank Cleaner - Remove Sludge, Varnish & Other Deposits - Rejuvanate Old, Stale Fuel - Concentrated Formula Works In Gas Tanks & Diesel Tanks".
 
I have only just taken out, cleaned out (it was pretty bad with rust, silt and very, very old fuel) my tank on the S2 coupe. I would strongly recommend that you do the same if you can. I lined mine afterwards with a polyurethane solution, which does its best to ensure, there is no further particles to clog up the carb. If you can set up a remote fuel supply, that would be good but not sure if the Weber 32DIC works best with gravity feeding but let me. know how it goes please.
 
Update:
I installed the boat gas tank in the frunk, along with an electric pump and new gas lines. I cleaned the carb, and it runs better, but still pretty bad. It really only runs with the choke on full, even after being warmed up. What do I have to adjust besides idle speed.
 
Well, that is a good start. I would make sure the jets are cleaned thoroughly, no air or fuel leaks as it sounds from your description, you make have either or both. The fact that you have to have the full choke on, suggests the mixture is lean, which often (but not always) indicated by the rough idle and need to enrich the mixture, caused by an air-leak. I had overlooked these on my old Californian, 850, with a special inlet manifold with an hidden inlet tube for emissions etc. For weeks, this played havoc with my attempts to run, drive and tune the car. I sprayed WD40 around the base of the carb, this made the revs fluctuate wildly, leading to my deduction and fix.
If no pipes or ducts, check the base of the carb, has it been bolted onto new, decent condition gaskets? These do leak, the studs aren't that strong and tend to wear out, even a tiny amount of air getting into the carb 'down stream' will destabilise the idle.
 
If you can use compressed air, this will also remove any particles. I used acetone, which is a really good solvent for old, degraded fuel, oily deposits and grease, which does cause dirt to stick to the sides and inside the jets.
 
Weber. Pics:
 

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