what would cause a 2001 4.7 to run only on the 2468 cylinders? i pulled the wires on them and tried starting it an it wont run of 1357. should i try swaping the coil packs from one side to the other? any help would be great! thanks

 

i have to ask why you think its only running on 6 of the 8 cylinders? is it running rough? i would expect with 2 cylinders down it wouldnt run at all (if it did it would be VERY VERY rough, hell one cylinder down makes a big difference)

 

Welcome to DF
I would start by doing a compression test and pulling the valve cover off and inspect for broken springs or follower coming off the valves. I also agree the motor shouldn't run at all with that many cylinders not firing.

 

Thanks for the welcome! yes the truck runs rough. i thought i had bad coil packs do to the manifold on the 1357 side was cold you can touch it. so i swaped coils from on side to the other and still no go. I tired pulling codes by turning the key on and off and it showed no codes. i then pull the coil wires on 1357 and the truck started and threw codes. i put them back on and pulled 2468 and the truck would not start of off the 1357 side. i am getting fuel on the 1357 if you pull the plugs you can see and smell the gas on them.

 

Crank sensor first, or cam sensor.

 

Possible but I don't see how this would stop an entire bank from firing? I'd look for a melted / damaged wiring harness where the cables split off to that side of the engine.

Are you SURE you have gas going to that side? Possible blocked fuel rail stopping / limiting fuel flow on that side? Same thing on the injector wiring harness for that side of the motor.

You should also be able to check for voltage at each of the suspected plugs by pulling the connector off the coilpack and hooking either an ANALOG meter to it (or use a 12v bulb and some pigtails). Cranking the engine should determine if there is voltage going to the low side of the coilpack. A digital meter will most likely not be quick enough to display any results.

Other than that maybe a wierd ECU problem? Is there compression on that side?
Bob

 

I've seen them throw some funky signs before,


But yea I think I'm on board with you as well. First he needs to determine if it is spark or fuel related. Then follow the problem up line.