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420A Fuel injector 4 not firing.

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AM2SS

Probationary Member
11
0
Jul 23, 2023
Longbeach, Mississippi
Check all the grounds in the ecu harness also. The ecu grounds out the injector circuit to fire the injectors. If there is a broken ground wire than the ecu won't be able to ground the circuit. Get a digital multimeter and check all grounds in the harness for continuity to ground. If all are good than test continuity from all wires to ecu from injectors than check the wires for the cam and crank sensors.
Question, is there a ground for each injector? My #4 is not pulsing fuel. And I have already replaced the cam shaft position sensor, spark plugs, wires and the coil pack.
 
Question, is there a ground for each injector? My #4 is not pulsing fuel. And I have already replaced the cam shaft position sensor, spark plugs, wires and the coil pack.

The ECU is the ground, the injector driver (one per injector) in the ECU pulls the one side of the injector coil to ground while the other side is connected to power (via the injector resistor on the turbo cars).

Please fill out a profile for your car so we know what kind of 99 it is. There is a large difference between the NA and Turbo 2G's
 
Well I took my injector harness to work pinned it out and it works fine great ohms great everything what would be next in the link on my way to the PCM? Is there is there a history of bad wiring or should I just pin out the main connector to the PCM
 
Done.

And I put the harness back in still not firing on number four. I just pinned out my harness from one end to the ECU and I have good continuity between all four of the wires so is there anything else or is it the ECU?
 
Have you at least pulled the ecu and looked for obvious damage? Once you verified wiring I think it would've been the first place I went.
 
Have you at least pulled the ecu and looked for obvious damage? Once you verified wiring I think it would've been the first place I went.
Most ECU's are sealed units. Can these be opened up without damaging them? Also I just ordered a I.A.M, idle air motor. Mine was out of spec by about 7.5 ohms.
 
Most ECU's are sealed units. Can these be opened up without damaging them?

Most turbo ECUs are not a sealed unit. Problem is we don’t know what year or model your car is.

Is it sealed? Idk you could have a 420a for all I know.

We can’t answer your question without knowing what you have. Fill out a vehicle profile with the modifications done to your car. We can’t help you unless you help us help you.

-Daniel
 
Not sure if my profile has been released yet but here is the info, she is a 99 Eclipse 2.0L non-turbo. I have changed the spark plugs w/NGK copper, wires, coil pack, cam shaft position sensor, throttle body position sensor, the fuel filter, fuel injectors. And yesterday I ordered a idle air motor (valve) because it ohmed out of spec.

It still idles badly and lags when I give it gas and it slowly comes back down to idle after that. Today I will ohm out the MAF and manifold temp sensors. I hope will be enough info if not just ask and I will tell you what I know, thank you for the assistance.
 
If the problem is just with the Injector on #4, all that other stuff isn't likely to be related.

Since you have a 420A based car your ECU/PCM is sealed up (potted) and there really isn't much you can do inside. I don't know if the 420A ECU will cut off fuel to a cylinder that is misfiring but it's something to investigate.

I forget, do you have spark to all the cylinders, what's your compression, have you swapped the injector to see if it works in another cylinder, and have you measured from the ECU to the injector to make sure the wiring is good?
 
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