Won't Stay Running

[Z Tyler Z]

1976 280z

Ok after some major testing/troubleshooting I'm still completely lost. I'm new to cars and in need of some ideas.

Here's the story so far.

Cars starts and runs great. I leave it sitting for about a week. When I get back it refuses to start. Sometimes it'll start for 2-3 seconds then immediately dies, even if I have the gas pedal floored.

-The starter is fine and turns the engine like a champ.

-I've used a light gun and every spark plus is getting a spark and so is the coil

-The fuel pump is working

-There are no worn pvc areas or leaking areas in the air intake.

-The air intake thing is turning on the fuel pump like it should.

-Changed the fuel filter, checked the returning line to make sure fuel is flowing good and it is.

- I checked the plugs and they didn't seem that wet.

Here is a list of dumb mistakes that I have done which could have lead to this problem

-hooked the battery up backwards and tried to start the car.

-While jumping the car I again hook the battery up backwards (to the other car) and caused soem big sparks before I unhooked them and corrected my mistake.

- The magority of the wires leading to the hazard area are unplugged (a lot of blue and green wires)(I doubt this has to do with not starting but I thought I'd tell you guys everything)

-When testing fuses I hit the tester against the bottom 3 fuses all at once and it seems to turn the engine. (bottom fuse on left with the 2 bottom ones on the right) This was after the car already wouldn't start. I have no clue why it turned the starter because according the the fuse box none of those fuses have anything to do with the starter.

-Ran the car pretty low on gas before I filled up the tank.

One guy I know says I could have fried the ECU unit by placing the battery backwards.

Anther guy says I might have clogged up my PVC, despite the return fuel line working.

Is the fuel pump suppose to turn on when the car is in the on position? Mine seems to only turn on after I try and start the car.

Any ideas? I really need some advice I don't have much money to throw away just replacing random parts until the problem fixes itself. I have the next few days off of work, so I have plenty of time to try your guys suggestions.

Thanks.

[khoist]

best advice is to take a noid light and see if injectors are getting a signal...If it is F/I...(just taking a guess it is)

Edited August 24, 2009 by khoist

[Weasel73240Z]

You seem to have a lot of stuff going on, but based on what you've posted so far, I think you clearly have an electrical issue. I think I'd be looking at the ECU, and the injectors. Get a multimeter, and start testing stuff. Maybe locate a back-up ECU to try. I might have an extra ECU at home, it came with some parts I bought a year back. Let me know if you need one, we can work something out.

Running the fuel tank almost empty could have pulled some crud into the line, which could make the car shut off after a few seconds of running.

[Z Tyler Z]

Guess I accidentally unplugged the ECU at one point of time and didn't realize it. Plugged it back it and she fired right up. Timings off by a bit but I'll get to that tomorrow. She idled for a while but slowly died.

Thanks for all those who helped me. I'm so happy I might be able to finally drive it for the first time tomorrow =)

[KDMatt]

Hey Tyler, glad you brought her back to life...

Is the fuel pump suppose to turn on when the car is in the on position? Mine seems to only turn on after I try and start the car.

Well, technically, according to what I've read, the pump is not supposed to run when it's just in the "on" position unless the engine is cranking or running.

There is a kill circuit in the Air-Flow-Meter (I think you referred to it as the "air thingy?") that makes sure that no gas is pumping unless the engine is spinning, as that would create a hazard if the car ever (heaven forbid) got into a wreck.

However, I'll tell you that in my '76 I CAN hear the fuel pump when I just click the key to 'On' ... the wiring in mine is a little shady in some spots though.

In short, I believe what you're experiencing with your pump is normal. Enjoy the car.