My neighbor has a 2000 f150, 5.4 liter gasoline v8. The number 4 cylinder is not firing, additionally the injector is not putting any fuel in the cylinder either. We swapped coils, and plugs, problem stays in number 4 cylinder. He had a new computer installed (not my suggestion btw) but problem persists. Do you fellas have any ideas? I am trying to get a chiltons on order so I can see a wiring diagram, I'm wondering if the injector has any bearing on the coil, with respect to getting a fire/no fire order? What is upstream from these components? Thanks in advance!

 

Is there a misfire code for that cylinder?
No fuel injection no fire.
No ignition no fire.
Both result in the same end result.
Has the injector been monitored for operation?
Is the injector plugged or faulty in some way.
Has the the injector been tested for 12 volt power present?
It could be as simple as a faulty plug or harness.
Has a compression test been done?
No use looking in any other area for a cylinder misfire without supporting codes.
Proper diagnostics would have prevented the expensive PCM replacement and programming involved.
Since the PCM has been replaced the drivers for the coil and injector are no longer a possibility.
I would test with an Ohm meter looking back at the PCM driver switches as a test the harness is not open.
This test should see about 10,000 ohms for a good test. No short or low value or no high value indicating an open or high resistance.
Do a compare with a good cylinder for both readings.
Good luck.

 

Is there a misfire code for that cylinder? - Yes there is.

Has the injector been monitored for operation? Yes and it is not getting a signal to fire, same with the coil

Is the injector plugged or faulty in some way. Not suspected, no signal is coming telling it to fire.

Has the the injector been tested for 12 volt power present? Yes, no power present.

It could be as simple as a faulty plug or harness.
Has a compression test been done? No, the other 7 are running, I just need to get #4 running too.

No use looking in any other area for a cylinder misfire without supporting codes. - I will get the code and post it.

Proper diagnostics would have prevented the expensive PCM replacement and programming involved. - I concur, but some people wait until the last minute to ask for help.

Thank you for the help.

 

In your reply, unless a mistake has been made, your problem is right in front of you.
The injector .....must....have 12 volts standing on it to be switched by the PCM driver's ground application.
Find out why and the issue will be solved.
Good luck.

 

Well that's my question and where i need pointed is, what is up stream of the injector that would give me this issue. Second, would the injector not getting a signal also cause the coil to not fire. Both are not getting signals to "work". If the cpu is upstream then i know i have a broken connection wire between the cpu and injector, and if the injector works inline with the coil that should solve both issues. Do you agree? Sorry all my vehicles are 76 or older, trying to help out a neighbor, but i greatly appreciate your help.

 

Oh just re read your post, thanks! Now, would the injector not firing also cause the coil to not fire? Meaning, are they conected electrically or do they operate independantly of eachother?

 

The coil and injector are fed from the same 12 volt supply fuse.
If neither has 12 volts there is a harness issue.
They operate but are switched independently because they do not operate in the same time frame.
Fuel has to be injected 'before' coil can fire the charge.
This means the fuel is sprayed through an open intake valve many crank degrees before the intake closes and compression begins.
Ignition timing usually is in the range of 0 to 30+ degrees before top center so fuel is introduced before this time frame when the intake is open.
This is why there is a cam position sensor to reference the intake valve positions as a separate function.
Good luck.