questions about 330 GT 2+2 fuel system

None of the diagrams are correct.

1.Line from tank to main filter.

2. After filter, line splits with one going to the electric pump (should be only one electric pump), and one line going to the mechanical pump.

3. Line from mechanical pump to glass bowl filter and then to front end of fuel rail at carbs.

4. Line from elctric pump to rear end of fuel rail at carbs.

5. NO fuel return line.

 

Hello Dyke, so both pumps are essentially a one-way check valve then?

john

 

The fuel pressure is adjusted by a straight slot screw on top of the regulators, or glass bowl filters.

 

That's the flow I have on my 330GT early series I.
At 4. above, fuel goes through another glass bowl/pressure regulator before fuel enters to the rear of the fuel rail at carb. #3. The glass bowl/regulator is hidden by the windshield washer bag.

 

John: Correct both pumps have one-way valves in them, however dirt can get under the flat valves in the electric pump and cause the fuel to be just pumped around in a circle with very little getting to the engine.

Starting with 330 GTC's, Ferrari added a calibrated fuel return line to the tank to fight the tendency for the fuel to percolate in the lines with the boiling pressure causing the needles to pop off their seats and dribble fuel down the carbs on hot soak conditions.

 

On a factory system with only a glass bowl filter/regulator after the mechanical pump, only the mechanical pump output is regulated. The electric pump pumps at only about 3 psi, so it does not need an additional regulator.

 

Thanks Dyke, good to know re the electric pump. Seems like it should come out from time to time for a cleaning.

john

 

Late 330 GTs (after ~8250) also had the small fuel return line.

 

This is correct. Good job.

 

It looks like the mechanical pump path is filtered twice. Great thread - I always thought the electric pump was a feeder for the mechanical pump, so it is helpful to know how it actually works. Given this, I can't help but wonder why they need the mechanical pump at all - it seems like just the electric pump would be sufficient.

 

Peter: Actually, it is the other way around. The cars were designed for the main pump to be the mechaincal unit. The electric pump was there to fill the carb bowls for cold starting and to add extra fuel on long high speed runs, or to help when the mechaincal pump vapor locked during a long period of hot idle condition. When everyting is working correctly, the electric pump is never needed when you are driving the car in normal conditions.

 

Thanks Dyke. I do recognize that the electric pump is just a helper for starting and I use it as such, but with so many other cars that have only an electric pump I wonder why Ferrari used both. Of the two pumps, the electric seems more necessary because it is needed for initial starting, so then why have the mechanical pump? I guess for one thing, the mechanical pump doesn't make the clicking sound. Could it be there is some benefit to the mechanical pump output varying based on RPM or are both pumps there just to add redundancy for reliability?

 

Steven: The tiny line from the rear of the fuel log is a "return" line to the fuel tank. It has a restrictor in the end of the fuel log that only allows a small volume of fuel to flow back to the tank, thus keeping adequate pressure and volume to the carbs. The purpose of this is the relieve the build up of pressure in the fuel system when the car is shut off and "heat soaks" the engine. Many times, this heat soak will cause the fuel in the lines to boil and the resulting pressure will force the carb needlles off their seats and let unwanted fuel overfill the carbs and flood the engine. When the engine is hot, this system also allows some constant flow of cool fuel to the log, even when the engine is not needing very much (idleing).

 

Peter: You will notice that the cars using electric pumps only, use Bendix (Facet) pumps. It is my guess that even Ferrari knew the Fispa electric units were not totally reliable, so they did not ask them to run all the time, but used them as secondary supply sources for fuel. The Ferrari and Maserati race cars of the era used FIMAC rotary mechaincal pumps assisted by one or more Fispa electrics, but never only Fispa electrics.

 

That's interesting, why did the early 330 GT had 2 in-line fuel/filter regulators (glass bowl type)?

330 GT Parts book TAV. 8 does show #13 as FISPA 3064-02 "Filtro regolatore benzina' Quantity 2.

Was there a problem on the early 330 GT fuel system that the factory had not yet quite solved by production time?

 

I agree that there are some 2+2's with two glass bowl filters. I have no idea what the reasoning was for using two filters, and the factory quickly switched back to just the one unit after the mechanical pump.

 

As you are saying above, in your post #17; that's probably the reason why after engine shut-off when "heat soak" sets in, the fuel percolates in the carbs and flows down the throats until fuel pressure is eventually relieved. The rear glass bowl filter/regulator prevents the fuel from returning to the tank and quite possible maintaining pressure. That's the reason why when I park my 330 in the garage with a hot engine, I leave the hood open to let the heat and the gasoline fumes out, turn the garage fans to air out the place and cool down the engine.

 

Van: I do the same thing when we come home after a drive.

 

Ahhhh, the things we do to keep on driving/enjoying these machines!!!!!!!!!!!!