I’m a younger kid and I just recently got a 1978 280z. The car will turn over and fire but it will die after I let go of the key or shortly after. I have test the spark plugs and got a new fuel pump. I also shot out the fuel rail and am running the fuel pump right out of the fuel rail. I can’t figure out why it won’t start and would like some help please

Let's be specific and precise. Is there still a plate in the driver's side door frame? Can you read the date? What I post assumes that this fits into what is considered the 1978 model year.

If I understand you correctly, when you put the key in the START position, the solenoid engages the starter. The starter turns the engine, and the engine fires. (The car starts.)

When you release the key to allow the switch to go from START on ON, the car dies immediately or shortly after. (It doesn't run.)

I'm not sure what you mean by running the fuel pump right out of the fuel rail. I will have to assume that you have an adequate supply of good gasoline to supply the fuel pump.

Here are two possible causes for your problem (though there can be others):

1. The back part of the ignition switch is failing.
2. The circuit for the fuel pump relay is losing the ground at the oil pressure switch.

How to diagnose (You will need a multimeter, i.e.: a meter that can measure voltage and resistance.):

Ignition Switch

1. Put the meter on DC voltage. If it has ranges, select the lowest range that is above 12 volts (probably 20).
2. Put the positive lead of the meter on the positive terminal of the coil (black wire with white stripe). Put the negative lead on an unpainted surface. I like the bolts of the shock tower.
3. Have someone start the car. You should see around 10 to 12 volts while starting. When the key is released to go from START to ON, make sure you still have voltage.
4. If the voltage drops to 0 when the key is in the ON position, that means the switch is bad.

Oil Pressure Switch

1. Put meter on the lowest resistance range.
2. The oil pressure sender has a "T" connector. The oil pressure switch connects to the vertical of the "T". Get one probe in the back of the wire to test. The other probe goes to an unpainted surface. Again, I like the shock tower bolts.
3. Have someone start the car. As the car starts, you should see the resistance measurement go to zero (continuity). If the resistance does not drop, that means you don't have the probe positioned properly, or the oil pressure switch is bad.

Let us know the results of these tests. Also, post pictures of you holding the leads in place and of the meter. Please don't post potato quality pictures. Sometimes people don't use the proper technique, and that provides bad results. I don't want you throwing parts at the problem. That gets expensive and frustrating.

11 hours ago, silentbug said:

 running the fuel pump right out of the fuel rail. 

What does this mean, above?  

Is the ignition system stock?  And is the rest of the car complete?  There are several things that need to be connected to get the injectors to open and close. 

It might be that the EFI system doesn't have power and it's starting from the cold start valve fuel.  You'll need a multimeter or test light to make much progress.  Check the EFI system fusible links.

Will it crank and idle? Dies out when you give it gas from the pedal?

Just reading the cold start valve running the car. That's a good point.

I had a bad tank in the car so I made my own using a gas can and hooked it up to the exit and entry parts for the fuel rail
The ignition system is stock and everything should be completely
Won’t idle for more the 5seconds and if it idles it sounds rough
The gas pedal get stuck when you push it down


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I would check the throttle plate in the throttle  body.

The sweeper vane under the black cover on the side of the AFM to make sure it moves freely. 

Then maybe the idle contact on the TPS, the other black box.

How long has it been sitting?

It has been sitting for at least 5 year and I have already checked the AFM and it seems to be working correctly


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1 hour ago, silentbug said:

I had a bad tank in the car so I made my own using a gas can and hooked it up to the exit and entry parts for the fuel rail

What kind of fuel pump did you use?  You need a high pressure fuel injection pump and high pressure hose.

If you're going to make it run right you'll need these.  The 1980 book covers all the way back to 1975.

 

The was running when was put in storage


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Thanks I have been look at some manuals to buy and the fuel pump that I bought was an aftermarket on built for scars it puts out around 40-45 psi


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*Zcars


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30 minutes ago, silentbug said:

Thanks I have been look at some manuals to buy and the fuel pump that I bought was an aftermarket on built for scars it puts out around 40-45 psi

Did you get the hoses connected right and the wiring too?  The pumps will run backward and if you connect the pump to the return line it will be blocked by the FPR.

Your best option right now is to get a decent meter, volts and ohms, and take some measurements.  Confirm that you have power to the injectors for one thing.  If the injectors don't have power they won't do anything.  Kind of seems like you don't have injector power.  You probably have a bad connection at the EFI fusible link by the battery.

You can do one thing at a time and think between each one or you can spend an hour and take a whole bunch of measurements.  Write down the numbers, whatever you decide.  "Good" is not as good a real number.  Good luck.