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Hi! im new to this forum! greetings from Costa Rica!

I bought a 240 on jan. with stock KA24E, the thing is that the previous owner remove all the fuel injection system and installed a carburator. I guess that the ECU went bad or something. The car has this external "diesel gasoline" fuel pump and went bad on a trip so I had to tow the car, doesnt run at the moment. I checked the fuel tank and there is not an internal fuel pump. I want to know. Can I install an internal fuel pump without ECU and fuel injection system? or is it necessary to have those two things to make the internal fuel pump work? is there a way to make it work even if I have to use a switch? I dont have the fuel injection system, previous owner said the he scrap them. im planning to install the system again once i foun one that for sale or maybe swap the engine. but thats a thing for the future
 

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You don’t need an ECU to make an in-tank fuel pump work. The fuel pump itself just has a 12V motor. And on a stock setup, the ECU simply switches the fuel pump on via a relay. This is no different from just using a switch to control the fuel pump. You could also just control the fuel pump by the ignition switch. This would best be done with a relay, although you would have to wire the stock EFI relay to trigger by applying +12V to it (the stock relay on an S13 triggers by grounding it). But regardless, you don’t need an ECU to run the pump.

A bigger issue is going to be fuel pressure. The stock fuel pump is designed for EFI, not carburetors. And as such, it is designed to provide fuel at fairly high pressure (43psi max, in the case of an S13). Carburetors require a fuel pressure of just a few psi. You will therefore need some way of bringing fuel pressure down. I have to admit that I don’t know much about carb conversions. But people DO do this. I am sure you can find some sort of pressure regulator that you can connect to your fuel supply and return lines that can supply fuel at low pressure for a carburetor.

Of course, an alternative is to just replace the fuel pump with another external fuel pump designed for carbs. A wide variety of such external electric fuel pumps are available for carbureted vehicles. Going in-tank would be better if you plan to eventually go back to EFI. But replacing the external fuel pump with another one would be a simpler and cheaper way to go if you need to be able to use your car immediately.
 
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