1975 280z control unit

[chevzee2]

1975 280Z - could use some advice on how the control unit (fuel injection brain) hooks up...??? There are two white wires with female butt connectors coming out of it that are not connected to anything. It will start and idle, but accelerating makes it run like it's getting lots of air, but no fuel. Four of the injectors seem to be working, but two don't. Any suggestions would be welcome!

[2ManyZs]

Since I just sold my 75 I don't have anyway to check to see what if anything the white wires are connected to. I remember seeing them at the ECU but can't remember where they went to. I let the service manual go with the car so don't have that for reference either. Seems to me they weren't connected to anything but I may be wrong.

If you are certain 4 injectors are firing and two aren't, then I would guess the problem is in the wiring harness or connectors to those two injectors. Be very careful when you take them off the injectors as they become very brittle with age and will fall apart in your hands. I would almost bet the plugs on the injectors are the problem. Replacement plugs are available, you can get them from MSA if you need them, along with the wire clips for the plug-ins. If you don't have a Motorsport Auto catalog I would suggest getting one, they can be a life-saver for small things such as this. You might be able to find replacement plugs at the local Nissan dealer, but they may not have them in stock and the price may be higher.

To check the injectors you can use a long screwdriver as a

"stethoscope", put the blade on the metal retaining ring around the injector and put your ear to the handle, you should hear the injector "clicking" as it opens and closes. No noise, you have found the problem injector, then it will be a matter of checking the wiring connections.

Hope that helps a little....

[chevzee2]

Thanks for the leads!

One more injector question...at idle there is power to every injector, but when you open throttle, it doesn't seem to make the injectors react. It seems to feel a lot of air, but no more fuel. ???

Happy to say that the MSA catalog was the first thing we got - even before draining the 4 inches of water and tadpoles out of the floor - I'm sure there will be more quesitons before it's over and your help is very appreciated~!

[2ManyZs]

First thing you need to do is establish whether or not it's an electrical problem or a mechanical one. It could be either.

Using the screwdriver method I described, find out if the injectors are firing or not when you rev it up. If not, it may be a problem in the air flow meter(mounted on the plate in front of the throttle body), either in the wiring harness itself or the potentiometer inside the AFM.

If they are working it could be the fuel pump is the problem and not supplying the correct fuel pressure to the rail to supply the injectors.

Best bet would be to check each and every wiring connector and make sure they are clean and securely connected. Then check for a fuel problem, may be the fuel filter is stopped up or the pump itself is not working properly.

If you don't have one already, you should get a factory service manual from MSA, they are a bit expensive but they are worth the money when working on the Fuel Injected cars, there are a lot of tests described in them that you can do to find the problem rather easily with just a couple basic tools.

[chevzee2]

Thank you for the suggestions! Very helpful to have some ideas of where to start!!

[St.stephen]

Please do not leave out the pressure regulator on top of the fuel rail! This little nuisance loves to create problems.