fuel pump constantly running

[raltz]

hello, i have a 1972 datsun 240z, and i noticed on the on position i hear the fuel pump engage and run, but it constantly runs, i was wondering is this normal? shouldn't it shut off, i left it on the on position for a long time without starting it, just to see if it eventually shuts off, but after about 20 minutes i still hear it running

[olzed]

If you have an electric pump, it will continue running.Just ignore it.

Edited September 29, 2010 by olzed

[Carl Beck]

...it will continue running because.... you have a fuel return line to your tank, for fuel not used by the engine...

If you have triple Webers for example, and you have eliminated the return - it will continue pumping when ever the fuel pressure drops in the pump... in that case you will hear it pump every few seconds once the lines are full...

[raltz]

ah thanks guys!!! i thought something was broken, damn thing sounds like a fish tank,

[BrianL1987]

Was recently suggested to me that I block-off the fuel return to prevent the fuel pump from running constantly. Any opinions on whether this is a good or, bad idea? PS: I have a 73' 240 with round tops

[psdenno]

Was recently suggested to me that I block-off the fuel return to prevent the fuel pump from running constantly. Any opinions on whether this is a good or, bad idea? PS: I have a 73' 240 with round tops

Does your fuel pump deliver a constant flow or deliver only on demand? Seems to me that blocking off the return line makes no sense as the pump will continue to pump and the excess fuel has to go somewhere.

Why do you not want the pump to run constantly?

Dennis

[BrianL1987]

I think that it will stop when pressure is reached (is that considered on-demand?). It is a Holley "Red" from Motorsports

[beandip]

Was recently suggested to me that I block-off the fuel return to prevent the fuel pump from running constantly. Any opinions on whether this is a good or, bad idea? PS: I have a 73' 240 with round tops

On your Z the pump will run until you switch the key to the off position. This includes if you ever crash and or end up on the roof!! I installed a pressure switch into the circuit, so the electric power is disconnected if the oil pressure drops below 5 or 7 psi. This safe guards both the engine in the event of a oil pump failure, or if I have a accident and cannot get to my key to turn things off. It is a simple mod. Your local Parts store has the pressure switches and all you need to do in buy a Tee and install the Tee into the engine block where the oil sender is attached. Mount the sending unit on the Tee and the pressure switch on it also. Buy a pressure switch that has two male spade connectors and switches at 5 or 7 psi. Just fab. two wires that run from this switch back to the green wire that comes from the fuel pump. This is your hot wire , and it is located above the foot well on the passenger side of the car close to the center console. Now when you start the engine, it will start and run on the gas in the carbs and as soon as it has oil pressure the fuel pump will run. DON'T BLOCK the return line. It is there , for one thing, to keep the flow of gas in the fuel rail , thus keeping it cool in the summer heat. Otherwise you will have gas boiling in the rail causing ''vapor lock''. I personally do not like the pulsating fuel pumps because they rattle and make noise. I use electric fuel pumps from RX-7s that are NOT injected. They are whisper quiet and pump just under 5 psi. They will supply S Us ,Tipples or 4 barrels. I have picked up several at the bone yards for $15.00 ea. for my friends. I keep one for a spare . I have used them for almost 10 years.

Gary

[BrianL1987]

Maybe I should check around for an RX-7 fuel pump. The Holly works great but, noisy as H*&&. Thanks, I wont block the return line

[BrianL1987]

What is best source for switched 12v for electric fuel pump? Mine was connected to coil but, robbed power at high rpm causing car to "cut-out". Now I have connected to battery with manual switch under dash (pain in but). I'm considering going back to mechanical pump. The noise bothers me too