280z cranks, but will not stay running.

[Zed Head]

i used a test light so +12 volts, and i pulled the plastic side cover off the a.f.m. for the test. I am running a w48 intake off of a maxima with the 280z wiring harness i have already swapped the throttle body because of the electronically controlled idle control on the maxima it will run for a minute very occaisionally but when it does it just dies my initial thought is vacuum leak but the starting fluid test did othing so all vaccum ports are capped and there are no leaks.

Pretty sure that some test lights don't need 12 volts to light. So you might be in the range of the ECU voltage, whatever it is, probably in the 5 volt vicinity. You should still measure resistance from the ECU connector. The pin numbers are in the drawing I attached.

The method for moving the AFM vane is okay, but the injectors still shouldn't click. Maybe what you heard was the fuel pump relay clicking, under the dash by the hood release handle. If the injectors are clicking when you move the AFM vane you should figure out why. They shouldn't be doing that.

I don't know what you mean by "electronically controlled idle control". Good luck with that. And in your first post you said the engine dies immediately, now you say it runs for a minute, so not too clear on what's really happening. Since you're running a different intake manifold and throttle body, make sure the BCDD (if the W48 has one) and the EGR system aren't leaking.

[theblackpearl]

so it runs intermittently sometimes it just fires enough to turn the motor faster than the starter. and sometimes it runs when running it will not rev or it will die it also idles at around 2500 there is no tach so its hard to pinpoint exactly. but it runs.... kinda. the bcdd system has a wire that has no mate on my harness. it is the factory bcdd system, and factory harness. im tempted to just save 700 and get su's from ztherapy. unless there's something that makes sense thanks for the help.

[theblackpearl]

fuel pressure regulator is out or giant vacuum leak but i did the starting fluid test for leaks (the one where you spray all around the intake while turning it over) and there are none, i also re- checked and re-tightened all of my bolts to my intake and we should be good

[mjr45]

Have you tested the FPR? Its a simple check, it sounds like you are running out of fuel, so I still think its the fuel pump switch, where ever that might be in your setup, you get enough fuel to start and run for few seconds then the fuel pump kicks off. I agree with Zed, the injectors should click when you push the AFM vane. A carb system is goign to run you about $900 with carbs, intake manifold, fuel pump etc.

[theblackpearl]

I rented the vacuum tester thing from autozone and the regulator held vacuum. So that steered me away initially, but heres the real cause for confusion.. my fuel pump is on a switch in the center console.

[poundz9oh91]

Was this ever resolved? I have the VERY same problem (77 as well). The only difference is that I've got an initial 9-10 volts showing at the fuel pump wiring under the passenger seat during cranking, but as soon as it starts, voltage goes back to zero and it dies. I've checked the AFM, Relay under the drivers side dash, FPR, ECU pins, thermotime switch, temp sensor, oil pressure sensor etc ... I'm at my wits end

[240260280z]

It is usually the switch under the ignition key that develops carbon on the contacts.

 

Replace it or remove and flush with solvent while turning.

 

It screws to the back of the ignition key mechanical assembly so the only thing you have to remove is the steering column plastic housing.

 

If I recall correctly there are two small philips screws behind the switch so you may have to stand beside the car and looks through the front wind shield as you turn the screws.

[Zed Head]

Kind of sounds more like the AFM contacts, if he's only losing power to the pump.  If it was the ignition switch he'd lose all power.

 

Details on the "checks" and whether or not this is a new problem on a car that was running or a problem that came with the car would help.  The easy way to check the AFM contacts is to turn the key on and move the AFM vane.  The pump should get power.  If it's quiet, you'll hear it running.  I've had my AFM contracts get dirty and kill power to the pump.  The engine would only start, run for a few seconds, then die.

[poundz9oh91]

I bought the car about 2.5 years ago and went through it from front to rear .. it seemed that I had everything ironed out. Running/driving etc. I got in it one day, drove it around for a bit and then stored it for a year .. when I pulled it out of storage, it seemed to be running fine in the driveway and then one time I cranked it up and it started all this .. AFM is new/rebuilt from MSA and have done all the continuity checks on all the components and sensors. This is why it's so aggravating. I was thinking AFM as well, pulled the plastic cover and checked everything as in the tech tips page .. and still .. a spike of 10v during cranking, then an immediate decline to 0 .. ugh

[Zed Head]

I don't think that the test I described is written up in the usual places.  And what you're writing doesn't tell much, but does fit a dirty AFM switch.  

 

The 10 volts is normal.  The starter drops the voltage as it uses amps.

 

You can test the AFM contact switch at the AFM, or at the EFI relay with an ohm-meter, but the easiest most direct test is to take the black cover off of the side of the AFM, or take the inlet hose off, turn the key to On/Run, then move the AFM vane.  If you have the cover off and there is power to the AFM contacts you might actually see a tiny spark.  The contacts look like a tiny set of distributor points and are actuated by a bent rod when the AFM vane moves.  It's very simple.  All it takes is a piece of hair or dust to hold the contacts open.  Probably why Nissan changed the system.

 

I would do that test. You'll know more than you do now.

 

Forgot to say - I have cleaned the contacts in an AFM with the striking pad from a book of matches.  Never did figure out what exactly was blocking it.