Carburetor trouble

J

James klesney

New Member
Hello I just got a 1972 fiat 850 spider I am trying to get it running again. It starts with the choke and I can keep it running as long as it stays above 5000 rpms. If it goes any lower it Boggs down and stall out. I tried rebuilding the carb and everything looks ok. Could it be the carb or maybe one of the vacuum lines. Are there any ways to troubleshoot the vaccuum system. Can I disconnect any of the lines or bypass any parts of the system to test. Any help is greatly appreciated. Thanks Jim
 
First of all welcome. Glad to have you here. Pics are always appreciated of peoples cars.

So I would start by going back through the carb to verify that all the various paths through the carb are in fact clear. Sounds like you have jets that are clogged or passageways that are clogged. You likely have some vacuum leaks, possibly at the base of the carb where it meets the manifold.

Your carb is likely one of the later ones with plenty of extra emissions stuff that isn't working. I believe Jeff Stich had a post about deleting some of those elements, though it may have been on the Mirafiori site. Alternatively getting one of the early carbs from a 1969 is a little easier to deal with as they really don't have much in the way of emissions.

As you can't get it to idle you haven't been able to check the timing but that may also be a contributing factor to the problem.

Jeff will hopefully swing by this thread and offer some more constructive suggestions, he has a large bank of knowledge far beyond mine.

In any case, welcome and hope to see and hear more about the resurection of your Spider.
 
If it is a 30DIC carburetor then you should expect some fun in diagnosing it. If it is idling at 5000 rpm then you have combination air leak and mis-configuration of the throttle/idle/stop screw settings.

First off, most of them have worn out throttle shaft bushings. There is no repair for this, so diagnose it first. To do this, cap off everything that isn't a fuel line using little rubber caps. Start the car. Use propane (unlit) or carburetor cleaner or starter fluid and spray it lightly around where the throttle linkages are on either side. If the idle wavers then you *might* have bad shafts OR the carb base/gaskets are bad.

From here you have to determine what to do. I wouldn't bother diagnosing a 30DIC frankly - I think they represent a low point in Weber carburetor quality. A bolt-on replacement is the 30DGS, available new from a variety of FIAT and Peugeot and Citroen places out there. http://www.ebay.com/itm/WEBER-30-DGS-NOS-CITROEN-NEW-MADE-IN-ITALY-/361623753648
The last DGS I bought didn't even need the mixture set - it worked out of the box. Wonderful, smooth idle.

If you decide to go for it, here's how I work on them: remove the carb and manifold, inspect and clean the surfaces, replace the gaskets and spacer, rebuild the carburetor, reinstall and plug every vacuum line, tune the car, reinstall the lines you need.

A photo of a 30DIC I wasted part of a day on in 1999:

1998_fiat850_0007.jpg
 
The DIC has a bad reputation but it can be made to run fine.
I have 850s that idle perfectly and run as intended with the DIC carb.
Why a low point? I admit the emissions add on's we're an after though but they can easily be removed.
There is a fix for worn out throttle shaft bushings, just like other Webers they must be re-bushed.

To each his own. Replacement carburetors are an option but by no means the only option.
 
I have had good success rebuilding mine and so far have not had to rebush the shafts. The kits are still available to replace the bushes and the shafts. Not cheap but much less than a new carb. Ymmv

My Coupe runs well with no issues. I have the earliest version so no emissions devices to speak of, the later ones not so much.

As Brad points out, fixing the likely vacuum leaks is your first step. The steps he outlines are good, you can also use carb cleaner as an alternative leak finder as the idle and running will change as you spray it on the base of the carb or onto the body of the carb. There are lots of places around the base of the carb that can leak:
Carb base to gasket, gasket to drain plate, drain plate to phenolic spacer, phenolic spacer to manifold, manifold to head (which should have a gasket as well). I don't recall if the spacer is above or below the drain plate so my order could be wrong but you get the idea.

I will look around for Jeff Stich's guide on modifying the later units to make them more reliable especially as they also have a larger secondary which is desirable compared to mine.
 
30DIC can't be rebushed; it has no bushings to begin with. The shafts ride on the casting. You could drill and bush them I guess, but with far superior substitutes available new for less money than a total rebuild, why bother? Most were Holleys anyway (which was just disappointing!)

I obviously don't like the carb, spent too many nights trying to make these work right and they never would. They're just not very well made.
 
other that solid idling, what other benefits should you expect with a 30DGS instead of a DICA? Better mileage, more power?


or should I just bite the bullet and go megasquirt (or other?) fuel injection?
 
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I've been driving my 850 Spider for about 7 years now, always with the stock 30DICA/30DIC1 carbs (been through several), and other than the idle jets needing to be pulled for cleaning periodically (a 5-minute job, tops), they actually work pretty well. That said, I'm intrigued by the 30DGS option suggested by Brad. Is there any performance gain with that carb?
 
Hi Guys,
I'm having a similar problem with my carb and I'm wondering if you guys have any ideas that might help me out. It's a 32/36 DFEV(new). The car was sitting for a long time (since 1984) so I know there was a little old gas in the tank (got most of it out but didn't remove the tank). I've been gradually diluting it with new gas it as I run through it but the mechanic who was working on it said that the idle jets needed to be pulled a couple of times to clean them out while he had it. It ran fine for a while after I got it back but now my issue is it starts up fine then when it warms up it dies. One of the symptoms I had before it started to die when warmed up was a little bit of surging when at idle. All the vacuum lines on the carb are plugged, I pulled the idle jets and hit them with some carb cleaner; they look good to me but I don't know if I should be letting them soak or something. I tried messing with the mixture and that didn't do anything good so I set it back to where it was. Right now the only thing that keeps the car on when warm is having the idle screw in so it idles over 2000RPM. I tried hitting the manifold with starting fluid and I couldn't hear any increase in RPM. I also swapped out all my old spark plug cables just in case it was a weak spark somewhere (swapped the plugs too).
 
I would pull the carb and do a complete cleaning of all parts and passages.

Carbs that have sat for an extended period need to be cleaned of deposits and verified for proper flow of air and fuel where needed.

From your description it is running lean due to blockages of the jets etc. you can pull the jets just as well as your mechanic.

I would consider running two fuel filters inline, cheap translucent plastic as a prefilter and a higher quality metal primary filter following it.
 
Last year when I was having nagging fuel system problems with my 850 Spider, I eventually got the car working right by draining the fuel tank, and replacing the fuel strainer "sock" attached to the fuel sender suction tube. There was a significant amount of rust in the fuel tank, and the original strainer sock was split and not keeping the rust particles out of the fuel lines. I replaced the sock with a VW Beetle part like this one: http://www.ebay.com/itm/like/221156217627?lpid=82&chn=ps&ul_noapp=true

Car has been idling and running great ever since. Suggest you replace that strainer sock before going any farther.
 
Interesting. I bet there is rust in there since it was sitting for so long. I'll give that a shot. I'll see about the dual fuel filters as well.
 
Hello I have a Fiat 850 spider 1973, I decided to go for the 30 dgs but I am having trouble tuning it, do you have a tuning manual or a troubleshooting for that specific carb? Thanks
bradartigue said:
If it is a 30DIC carburetor then you should expect some fun in diagnosing it. If it is idling at 5000 rpm then you have combination air leak and mis-configuration of the throttle/idle/stop screw settings.

First off, most of them have worn out throttle shaft bushings. There is no repair for this, so diagnose it first. To do this, cap off everything that isn't a fuel line using little rubber caps. Start the car. Use propane (unlit) or carburetor cleaner or starter fluid and spray it lightly around where the throttle linkages are on either side. If the idle wavers then you *might* have bad shafts OR the carb base/gaskets are bad.

From here you have to determine what to do. I wouldn't bother diagnosing a 30DIC frankly - I think they represent a low point in Weber carburetor quality. A bolt-on replacement is the 30DGS, available new from a variety of FIAT and Peugeot and Citroen places out there. http://www.ebay.com/itm/WEBER-30-DGS-NOS-CITROEN-NEW-MADE-IN-ITALY-/361623753648
The last DGS I bought didn't even need the mixture set - it worked out of the box. Wonderful, smooth idle.

If you decide to go for it, here's how I work on them: remove the carb and manifold, inspect and clean the surfaces, replace the gaskets and spacer, rebuild the carburetor, reinstall and plug every vacuum line, tune the car, reinstall the lines you need.

A photo of a 30DIC I wasted part of a day on in 1999:

View attachment 1037
Click to expand...
bradartigue said:
If it is a 30DIC carburetor then you should expect some fun in diagnosing it. If it is idling at 5000 rpm then you have combination air leak and mis-configuration of the throttle/idle/stop screw settings.

First off, most of them have worn out throttle shaft bushings. There is no repair for this, so diagnose it first. To do this, cap off everything that isn't a fuel line using little rubber caps. Start the car. Use propane (unlit) or carburetor cleaner or starter fluid and spray it lightly around where the throttle linkages are on either side. If the idle wavers then you *might* have bad shafts OR the carb base/gaskets are bad.

From here you have to determine what to do. I wouldn't bother diagnosing a 30DIC frankly - I think they represent a low point in Weber carburetor quality. A bolt-on replacement is the 30DGS, available new from a variety of FIAT and Peugeot and Citroen places out there. http://www.ebay.com/itm/WEBER-30-DGS-NOS-CITROEN-NEW-MADE-IN-ITALY-/361623753648
The last DGS I bought didn't even need the mixture set - it worked out of the box. Wonderful, smooth idle.

If you decide to go for it, here's how I work on them: remove the carb and manifold, inspect and clean the surfaces, replace the gaskets and spacer, rebuild the carburetor, reinstall and plug every vacuum line, tune the car, reinstall the lines you need.

A photo of a 30DIC I wasted part of a day on in 1999:

View attachment 1037
Click to expand...
 
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