Hi all,

this is a post of my problem and solution to a summer long fiasco. I went through the entire FSM multiple times, checking all sensors and ecu because I was getting severe rich condition. I’m talking washing cylinder walls with gas. I did find problems, but not “the” problem. I had a basic no start condition with the occasional sputter to life, and lots of eye watering gas coming out of the exhaust.

the solution: I noticed one day that I always was trying to advance the timing, and indeed it would spit and fire better at the max turn of the distributor. The car liked timing, but couldn’t get enough. Well it dawned on me that maybe my window of adjustment is in the wrong area. I pulled the distributor out to find it doesn’t have a traditional gear, rather a tooth that fits in one-way. I also haven’t messed with timing chains, or gears. What I did notice was when I took the #1 cylinder to TDC, the rotor button was pointing to it correctly, but the closest post on the distributor cap contained a spark plug wire that went to another plug. I originally thought, well this doesn’t matter, because my firing order is correct.

this is only true on carbureted engines.

you see, the phase in which the injector “clicks” is of the same firing order, but when the injector starts at #1, the rotor button is pointing to #1 at TDC. So if another plug wire is getting that spark, then there will be a spark with no fuel at the other location. Meanwhile, #1 gets a shot of fuel and compresses the mix to no spark avail.

the carbureted engines don’t care about fuel timing relative to spark because the intake manifold is having a cloudy mist of air and gas just ready to be pushed into the cylinder. Once the intake valve opens the mixture pours into the cylinder.

a fuel injected engine is much more precise and there isn’t time where the air and fuel get to mix. This is the problem.

Solution: check not only that you have the correct firing order, but be most precise at starting the number 1 plug wire at the location of the #1 cylinder at TDC.

otherwise you’ll hunt a rich condition until the cows come home.

 

Just an FYI, the fuel injection system for 280zx is a "gang fire" system. This means that all injectors fire at the same time. The ECU grounds all 6 injectors every 3rd time the ignition coil fires. Your issue was incorrect wire placement. If someone removed the oil pump and installed the drive shaft 1 tooth off, this will happen.

 

So, my question is do the injectors live in the intake just before the intake valve? If there isn’t any precise timing relative to each cylinder, then there must be a mixing stage. Then the intake valve opens and gathers the mixture.

Thanks,
Andrew

 

Yes. Remember that at 3000 rpm, the intake valve is opening and closing 25 times every second so there is not much time for fuel to pool anywhere. Injectors are pointed at the intake valves in the intake manifold.