Upgrading 74 Spider to 32/26 DFEV Carb

[fabioapproves]

Hi all. I know folks have posted about this topic here before, but please forgive me as I am a car noob self teaching my way through my first Fiat. I'm upgrading the carburetor on my 1974 Fiat to the 32/36 DFEV Weber carb (https://autoricambi.us/high-performance ... 2-36-dfev/) purchased on autoricambi. I've installed the thing but no fuel is getting into the carb. Also I am left with a mess of now unused hoses and ports and would like to understand if I have set the thing up correctly.

At the link below are some photos of the old carb and new. Can anyone help me identify which ports/hoses are which and help me understand why I can't get any fuel moving? If I detach all the hoses and try starting the car, still no fuel is moving through. Does it need vacuum to pull the fuel?

Many thanks!

Link to Google Slides with photos and questions: https://docs.google.com/presentation/d/ ... sp=sharing

[18Fiatsandcounting]

Lots of people have done this conversion, and it works pretty well, so I'm sure you'll get lots of input. One question: Do you have a mechanical or electric fuel pump?

As for the old carb, here are some answers, and I'll let others with more experience comment on the new carb setup. On your photos:

1 is the emission electrovalve as you note, which puts the engine in a higher idle (1500) when the clutch is engaged and the transmission is in 3rd or 4th gear. The idea was to reduce NOx emissions. You can plug this up. For reference, that black switch just barely visible in the lower right of your first photo is the test switch for the system.

2 goes to a side or bottom port (depending on which model you have) of the charcoal filter as you note.

3 is the fuel return. On the old carb, the larger brass fitting should be fuel inlet and the slightly smaller one should be fuel return. The idea (I think) was to circulate fuel back to the tank to "cool off" to avoid vapor lock. Since the DFEV was designed for many different cars (not just the Fiat spider), it doesn't have a fuel return, but there is a simple work around.

4. Yes, that should be the fuel inlet if it's the larger diameter brass fitting. It's been a long time since I owned a '74, but if it's like my '71, there are 3 metal lines from the fuel tank up the center tunnel to the engine bay: fuel in, fuel return, and vapor recovery (to the bottom of the charcoal canister).

5 should be a narrower diameter hose between the intake manifold and the top of the charcoal canister. It's narrower by design so that you don't allow too much extra air flowing into the intake which would goof up the carb operation.

6 is part of the Exhaust Gas Recirculation (EGR) system. It feeds some exhaust gas back to the intake manifold, which lowers the combustion temperature slightly and reduces NOx emissions. "This" in photo #3 is the EGR valve. The system also has a thermostatic switch on the intake manifold so that the EGR only operates when the engine is warmed up. The thick metal tube across the top of the engine is where the exhaust gases get fed back to the intake manifold (when that EGR valve is open).

Let's start with that; hope this helps.

-Bryan

[Nut124]

If you have a mechanical fuel pump, you may need to crank the engine for some time to fill the carb bowl. The mech pump is located on the side of the block below the intake manifold.

If electric, you should hear it as soon as key is turned. An electric pump is usually in the trunk.

The upper "??" on the new carb is likely the vacuum advance connection for the distributor. If not used, it needs to be capped.

No, vacuum is not required for fuel to fill the carburetor bowl. The pump does that.

Be careful when testing fuel delivery, keep good ventilation.

[fabioapproves]

Hi gang, sorry for the slow reply, and thank you for the quick answers! I've updated my photos with the new information (still accessible via the same link above).

To answer some q's: I have an electric fuel pump, which is located in the trunk. It was installed recently by a friend of mine who I really trust to know what he is doing. Still, I checked. It is getting power, and I can hear it pumping (or trying to pump. Interestingly the noise is quieter than I remember, but it has been sitting for many months now, so maybe my memory is faulty). I replaced the fuel filter and can easily see that NO fuel is making its way from the tank to the pump (new filter is still dry). I checked the hoses, which were quite crammed in back there, and they are very stiff and dry/cracking. I am going to replace these hoses and try again; maybe the pump is pumping but the hose is too badly damaged/kinked/cracked for it to draw fuel. Will update once I put on new hoses!

It sounds like both of the ??? ports on the new carb do not need to be hooked up to anything, so I will plug them. Unless... does hose #6 that is coming from the EGR valve go to the lower port? Otherwise I guess this hose needs to be capped?

18fiatsandcounting, you mentioned a workaround for the lack of fuel return on the new carb. Is there something I need to do there?

Thanks all!

[18Fiatsandcounting]

Fabio, yes, let us know when you replace those hoses as that may solve your fuel pumping problem.

As for the return line when you don't have one on your carb, you need one of these bad boys:
https://autoricambi.us/fuel-filter-carb ... turn-line/

Two of the connections are for the fuel from the tank and the return, and the output goes to the single fuel inlet on your carb.

-Bryan

[fabioapproves]

Awesome, thanks for the link! Will purchase this as well and report back

[fabioapproves]

For anyone interested in following this saga... I purchased new fuel lines and am glad I did as the old ones were not in good shape. But from what I can tell, the fuel pump is not pumping. It makes a noise, but no fuel moves through. It is getting power. I even checked the lines inside of the fuel tank that feed the fuel up to the fuel line and to the pump. All is fine. No instructions, no issues. Fuel tank is also brand new. Fuel pump is pretty new as well, so I am annoyed if it just up and died. Anyone know if this is a common issue? I can buy a new fuel pump, but I don’t want to throw money at this if that’s not the issue.

[RRoller123]

I was a bonehead and wired up my pump backwards accidentally. It ran, but nothing came out.

[fabioapproves]

Ha! I’m glad you found the fix. The weird thing for me is that the fuel pump used to work just fine. The car has been sitting for months, but the last time I started it, the fuel pump still pumped. Not sure why sitting idle would harm the pump, hence my confusion and annoyance.

[18Fiatsandcounting]

Let me ask what seems like a stupid question: How do you know the fuel pump isn't working? No gas at the carb, engine doesn't start (could be other reasons), or ???

Since you replaced all the fuel lines and you have a new tank, I'm thinking maybe the fuel pump has gone completely dry over the past few months and so it doesn't pump. Try priming it, and the easiest way to do that is to pull a vacuum on the fuel line up at the carb, drawing fuel all the way up the line. Since I tend to be a wild and cra-a-a-a-zy guy, I just get a couple foot length of clear plastic tubing, connect one end to the fuel line, and suck on the other end. Stop when you see fuel enter that clear plastic line. Ask me why I suggest a clear plastic tube.

If nothing comes up the line with a vacuum, you either have a leak or a plug somewhere in the lines or pump.

-Bryan

[jon8christine]

I recently did a 32/36 conversion...my topic may be helpful.

http://www.fiatspider.com/f15/viewtopic ... 53#p297514