Only one injector is firing

You are probably working on a ford. You say "still not firing". What have you done so far? Those 4 injectors fire off of bank 2. See following forum on this problem

https://www.ford-trucks.com/forums/1402491-injector-bank-not-firing.html

A diode test light 12 volts, or a noid light is used to test the injector signal to the injector. Need spark, fuel, and compression for an engine to run, got all three, then the timing or severe intake vaccuum leak can still keep the motor from starting.
I don't know if an alarm or impact switch is in its system.

if you have a $5 test light, you could find the problem. just know that all eight injectors have a constant voltage applied to them anytime the key is in run or start. and also that 4 of the injectors share a common ground, they have their ground wires spliced together before the ground wire enters the pcm to be internally grounded. and the other four injectors are the same- their ground wires splice together. so your four that don't pulse have lost either the power to them, or the common ground wire for the 4 may have broken. or lost connection.

it is easier to check the power side first, so clip a test light lead to the negative battery post or cable, turn the key to on,and probe each injector connector. one of the terminals at all eight injectors will be the power wire, and it should light up the test light. if all eight injectors have power to them, you know it must be a ground side problem. if you find that 4 injectors have no power to them, look for a broken splice in the power wire to all injectors. back in those days, injectors were "bank fired". one side or bank of the engine all had the injector grounds spliced together, so all injectors on one bank fired (pulsed) simultaneously, and then the other bank was fired or pulsed. that was good until sequential injection matched the pulse to the cylinder ready to fire, more precise, and in the modern systems each injector ground has a separate ground inside the pcm. no more splicing of the ground wires, and having bank fired engines.


when the pcm grounds the circuit, the injector coil is energized and the injector opens to spray fuel out. so the injector has constant voltage to it. only when the circuit is grounded is that power applied across the injector.

Check the grounds from the rear injectors to the computer. On a bank fired system as yours, all 3 injector grounds on each bank splice together before they go into the computer. Check wire continuity from injector to the computer connector with the ohmmeter.

Check for spark on the side not firing. If there is spark, the injectors on the right side may have a problem in the wiring to them. Older multi port injection systems used a "bank fired" approach: all the injector grounds on one bank splice together before they go into the computer to be pulsed.
All of the injectors have a steady voltage applied to them when the key is on. The same color wire to all injectors is the power wire, it is a fused circuit, the fuse is in the power distribution box, and is hot in run or start. When the computer internally grounds the injectors, pulse occurs and fuel is sprayed out. Check if the right side has power to the injectors with key on, use a voltmeter or test light. To test an injector circuit, purchase a cheap "noid light" from a parts store. You plug it into an injector connector, then crank the engine over. If the noid light is blinking, the power and ground circuit is good for that injector.

Possible jumped timing belt causing that side of the engine to be far enough out of time not to run on those cylinders.Check power feed to all injectors to make sure though.With the key on engine off,all injectors should have 12 volts

I would be very interested in helping you, but I need some help understanding your problem. Fuel injectors do not fire. The spark plugs do that honor.

If you are not getting current to eh injector that is another matter altogether. Please try and let me know how the car is acting. Will not start? does it start but then shuts down? Can you run current to the injectors seperately and start the car. You might want to check with your electrical man and ask him what he did or did not do. Please feel free to contact me at any time.

Check the pulse on the two injectors.Purchase a noid light at the parts store,that will fit the injector harness,see if the noid lights will flash,if they do,then replace the injectors,this would be the only thing it could be.If the noid light is not puling,or flashing,then the computer is the problem,seeing it is the distributor of the pulse on time.

what do you mean "no fire on 1 side of injectors??" 1 injector no firing?? or what?? was the engine that you put in there used?? from junk yard?? If so, put the injectors back from your engine onto the engine you just put in there.

make sure fuel is going to engine from injectors, you can try by adding carburetor cleaner to intake and crak it, if it runs for a little be then ijectors are not firing, some times the ignition module to control the spark will keep the injectors from firing