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Can someone please tell me about the fuel pump operation? The manual for my 76 280Z says if you disconnect the starter (S) terminal and turn the ignition switch to start - you should here the fuel pump running. I tried this and the pump would not come on. However, the car will start and idle fine. Can't drive it for other reasons (body work in progress), so I don't know if it would do OK under normal driving conditions. These are the questions I have: 1) Is it possible for the car to start and run without the fuel pump operating? 2) If the answer to question #1 is NO, then does the fuel pump run constantly when the car is in operation, or does it just come on intermittantly.
 

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I think the mechanical fuel pump is always on, but I'm not sure. I don't think the electrical fuel pump is always on though. But you need it to run your car. I just changed my elec. fuel pump recently and it ticks like a time bomb when it's on.. I had loose connections on it, so I guess it was on sometimes and off at other times, but my car still ran. Hope I helped in any way.
 

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> I think the mechanical fuel pump is always
> on, but I'm not sure. I don't think the
> electrical fuel pump is always on though.
> But you need it to run your car. I just
> changed my elec. fuel pump recently and it
> ticks like a time bomb when it's on.. I had
> loose connections on it, so I guess it was
> on sometimes and off at other times, but my
> car still ran. Hope I helped in any way.

If you have a 1976 280 you should have fuel injection. It will not run without the fuel pump in operation. Try making sure you disconnected the right wire on the starter. If you did indeed, you may have a pump that has been rewired in some way. Hope this helps By the way, I also have a 1976. Good Luck !
 

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> Can someone please tell me about the fuel
> pump operation? The manual for my 76 280Z
> says if you disconnect the starter (S)
> terminal and turn the ignition switch to
> start - you should here the fuel pump
> running. I tried this and the pump would not
> come on. However, the car will start and
> idle fine. Can't drive it for other reasons
> (body work in progress), so I don't know if
> it would do OK under normal driving
> conditions. These are the questions I have:
> 1) Is it possible for the car to start and
> run without the fuel pump operating? 2) If
> the answer to question #1 is NO, then does
> the fuel pump run constantly when the car is
> in operation, or does it just come on
> intermittantly.

Well, I have to disagree with your manual. Your air flow meter has a safety switch in it
that doesn't allow the fuel pump to run unless air is being sucked into the engine (or
you manually open the switch). Try your test again but this time pull the plastic cover
off the air flow meter and separate the contacts to the far left that open when you open
the air flow flap. The pump should run now. BTW, if your car runs o.k. then there probably isn't
a problem.

The answer to your questions are:

1) no, well actually maybe if there is pressure in the line but it won't run long.
2) it runs constantly, the fuel pressure regulator recirculates gas back to the tank at idle.
 

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Assuming the 280 is similar to the 260Z. I have two fuel pumps. Electric back at the tank. Mechanical right at the motor. The mechanical pump will pump fuel as you turn the motor over. The fuel 'pumps' via a lever actuacted as the cam turns.

The electric fuel pump is designed via relays to NOT come on while the starter motor is engaged and to cease pumping below 400RPM.

> Well, I have to disagree with your manual.
> Your air flow meter has a safety switch in
> it
> that doesn't allow the fuel pump to run
> unless air is being sucked into the engine
> (or
> you manually open the switch). Try your test
> again but this time pull the plastic cover
> off the air flow meter and separate the
> contacts to the far left that open when you
> open
> the air flow flap. The pump
> should run now. BTW, if your car runs o.k.
> then there probably isn't
> a problem.

> The answer to your questions are:

> 1) no, well actually maybe if there is
> pressure in the line but it won't run long.
> 2) it runs constantly, the fuel pressure
> regulator recirculates gas back to the tank
> at idle.
 
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