two fuel pumps

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Paulc
Posts: 3
Joined: Mon Oct 24, 2022 3:11 pm
Dino: Fiat Dino 2.4 Coupe

two fuel pumps

Post by Paulc »

Hi, I have just bought a 1972 Dino Coupe 2400 and am spending time looking at the changes it has gone through over the last 50 odd years. It needs a bit of work and there's a lot to do but after reading through the forum you seem to be a helpful lot, luckily for me and the car. I guess my first task is to try and get it back to some sort of originality which leads me to the fuel system. The car has the std fuel pump at the back but also has a second one fitted in the position on the front wing where the FIAMM air compressor normally sits. The second pump has its own fuel line direct from the tank dressed under the car next to the original. The std pump feeds into the rear carb as normal but the second pump feeds into the front. I've attached a sketch showing the two systems
two fuel pumps.pdf
(128.83 KiB) Downloaded 96 times
. I'm assuming the owner wanted more petrol in the carbs but it seems the wrong way to go about it. Any comments from anyone, was this a thing that was done back in the day? The way the entire second fuel system is taken from the tank meant that it wasn't a simple operation so they must have really wanted to do it! I thought it might be a back up system but if one failed I think the fuel would just be forced down the other 2fuel line.
Also the drawing shows a '4229820 union' on the forward carb rather than just a final connection, was the fuel line supposed to go elsewhere?
Thanks Paul
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Tobi
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Posts: 536
Joined: Thu Nov 14, 2013 7:56 am
Dino: Fiat Dino 2.4 Coupe
Location: Upper Palatinate - Bavaria

Re: two fuel pumps

Post by Tobi »

The 2400 has a fuel return line back to the tank. Is it possible that the second fuel pump is installed in this return line?
How is it wired? In parallel to the regular fuel pump?
Paulc
Posts: 3
Joined: Mon Oct 24, 2022 3:11 pm
Dino: Fiat Dino 2.4 Coupe

Re: two fuel pumps

Post by Paulc »

Thanks for the response. Yes, it could be a pump to pump the fuel back to the tank. I didn’t realise there was a return. I looked at a lot of engine pictures and I couldn’t see a return, was this just on the 2400? Unfortunately the wiring is a bit of a nest so I need to trace where the wires are coming from to know where it is powered from. Presumably so long as the original pump is still good I can remove the second one with no negative impact? Thanks
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Tobi
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Posts: 536
Joined: Thu Nov 14, 2013 7:56 am
Dino: Fiat Dino 2.4 Coupe
Location: Upper Palatinate - Bavaria

Re: two fuel pumps

Post by Tobi »

The 2400 has a return line while the 2000 has a single-line system. Usually there is no need to pump fuel back. The pump delivers constant pressure and the carbs take what they need. The surplus fuel flows back to the tank.
Try to sort out the wiring to find out why there is a second pump installed and what it is supposed to do.
Maybe this helps a bit: http://www.fiatdinoforum.org/viewtopic.php?p=4857
Paulc
Posts: 3
Joined: Mon Oct 24, 2022 3:11 pm
Dino: Fiat Dino 2.4 Coupe

Re: two fuel pumps

Post by Paulc »

thanks Tobi
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