280 z help please
 

Hi, I am looking for some help please, I know nothing about these cars, But have a friend that has a 1976 Californian 280Z 2.8 L28 engine, this is what I am told, and he cannot get it to start, It has fuel pressure, a good spark. He has 12volts on both wires on the injector. What I am proposing to do is put a Pico scope on both injector wires , turn the engine over and see if it is getting a signal from the ecu, He has checked all the power and grounds on the ECU.

What I would like if anyone can help , Is a good wiring diagram, This system has the dropping resistors, Can some explain in laymans terms how this system should work. It has a constant 12v feed to one injector wire and |I assume the ECU grounds out the other, Where does the ECU get the signal from to fire the injectors, On a normal car it it is either a cam or crank sensor.that sends the signal.to the ECU an the the ECU sends the signal to the injectors.


Or am I total wrong

Any help much appreciated.

I will get this car to run if it is the last thing I do.



Paul

A few seconds of googling :D

https://www.classiczcars.com/files/c...ring-diagrams/

As for the rest. Not sure. Haven't had a 280z in over 15 years.

The ECU counts the times that the ignition coil fires and on every 3rd coil fire the ECU grounds ALL of the injectors at the same time. Its called "gang fire"
Both wires on the injectors will have 12v unless you unplug them all, then you can check voltage and you will know which wire always has 12v on it when the key is on. The dropping resistor is there because the injectors are low impedance. They will draw too much juice and burn out without the resistor limiting the current flow. It reduces the current flow not the voltage. The Fuel Injection 280's used the resistor until 1982 when the ECU was beefed up enough to do the current limitation internally.
Just because you have fuel pressure does not mean that the injectors are injection the fuel. A Noid lite comes in handy to see if the injectors are being grounded to complete the circuit to open them.
There are lots of things that will cause a no run. Start at the fuel is you know you have spark. Are your plugs wet?
You can test the fire circuit of the ECU by using a wire to ground the coil with the ignition on. Hook the wire to the -Neg side of the coil and ground it quickly 3 time and listen for the injectors to click. If they click, it doesn't mean you are getting fuel thru the injectors. If you repeat the grounding of the coil several times (fire the injectors 4-5 times) and then crank the engine just briefly, you should see fuel on the plugs.
My 1983 had fuel and spark and air! It took me 5 weeks to finally prove it was a bad ECU. Don't give up!
Vacuum leaks, bad coolant temp sensor, bad air flow meter, air temp sensor so many things to check.
Try to find a 1976 Factory Service Manual and do the diagnostic checks. There is no way to check the ECU itself, you just check everything else and if all else fails, recheck everything 3 times and find someone with at good ECU and borrow it!
Here is a good general desctiption of how the Bosch L-Jetronic Fuel Injection system works. Knowledge is power.
https://www.mirafiori.com/faq/fiatFI_may2002.pdf