hi everyone! i have been going through some problems with my truck and cant figure it out. little info on my truck : 93 f150 2wd shortbed. originally a 5.0 with a 5 speed. it is now converted to a 96 f250 460 efi motor, 93 f350 460/5 speed computer and a 79 c6 automatic. after getting everything swapped in and plumbed up i have ran into a starting problem for it to actually run. when i turn the key on, there is no check engine light and it just cranks when tring to start, will not fire. i have fuel, air and good strong spark to the motor. i do have power to the coil, but i do not power to the fuel injectors or any of the smog solenoids. now if i run a hot wire from the battery to the main wire that feeds all of those componets, the truck will start and run perfect but still no check engine light. the computer is getting power to places it should and all grounds are good. i have no clue what to look for next. anyone else have any ideas on what it might be lol?

thanks alot,

mike

EDIT:: also forgot to say that the wire in question that i supplied 12v constant to, is pin #42 on the 42 pin connector for the engine harness side. the same wire on the other side of the connector has no power at all to it so i think thats the one thats giving me problems. it looks like a tan w/ yellow stripe colored wire on the body side, but is red on the engine side of the connector. the engine harness from the 96 f250 was an e40d truck so i dont know if that matters or not.

 

Sounds like you lost the ground on the fender near the battery on the passenger side.
In other words you do not have a ground of the PCM Power relay coil.

I have no idea how you are getting fuel.

 

grounds are good and clean on the fender to the battery. fuel pump cycles on and off as it should. just has no power to the injectors unless its wired to 12v direct. also cant pull any codes period on it no matter which way you try. its got me stumped lol

 

No power to injectors, good ground, can't pull codes...my guess is bad PCM.

 

i tried my old 5.0 computer to test and see if it was the pcm and its the same way. the 5.0 computer was good before i swapped it out. i traced all the power and ground wires and nothing was broke or chaffed. all fuses and the diode are good. no burnt fusible links anywhere. its driving me nuts lol

 

new update. tried to restart it after awhile and the starter kept engaging while it was running and wouldnt run right. soon as i shut the key off it died and stopped trying to engage. it was also running rich too. guess i will wait til monday to mess with it again lol. thanks for the help guys. this truck is becoming a money pit

 

The power to the injectors and the PCM comes from the PCM Power relay.
The PCM Power relay is operated by the Ignition Switch.

 

Bad guess.
Ding ding. All the solenoids, injectors, etc..receive 12V directly from the PCM power relay.

You have a fuse, relay, or wiring fault between your ignition switch and the relay.

 

He says he has power to the coil and good spark. The same wire from the Ignition switch that powers the Ignition coil also supplies power to the coil of the PCM power relay. So I would say there is an open in the ground wire for the coil of the PCM power relay or an open fuse to the common contact of the PCM power relay.

But then on the other hand he says the fuel pump is working OK and the PCM power relay also supplies power to the coil of fuel pump relay. But someone may have changed the wiring to the fuel system so it operates differently.

 

If he was jumping power directly to the 12v line of the injectors, then that would supply power to the fuel pump circuit.

 

got my starter situation fixed so thats out of the way. before i hot wire the injectors my fuel pump comes on with the key like its supposed to. that feed wire that runs the injectors and the other sensors is the one i have to supply 12v to to get the engine to actually run. ive never came across a problem like this before with these trucks lol. im thinking it may be the engine harness itself. the truck that the 460 came out of was a 96 f250 4x4 with an e40d and im using a computer from a 93 f350 4x4 that had a 5 speed. it looks like theres some wires in the harness that shouldnt be used and that might be grounding out something in the junction box under the hood. i have my old harness from the 93 302 that i might try to swap over to see if it makes a difference. the 93 f350 ran good and had no troubles before i pulled the ecm out of it so i doubt thats the problem. its just frustrating since the trucks been down since december of last year

 

On my truck with the 351W it's easy to test, maybe your wiring is the same or similar to make it easy to test? On my truck there is one pin/wire from the PCM for each bank of 4 injectors (so 2 wires for power) and then one for ground. Based on the PCM you have, you should be able to find the pin number for the power wires to the injectors. Trace them from the PCM to a large, square, 48 pin connector that goes in between the driver's side fender (inside the engine compartment) to the motor. This is where most of the wires for the sensors go to and from. The power for the injector wires will go through that 48 pin connector to a bank of injectors.

Like I said, this his how my 92 is wired. If yours is the same you can maybe find a place where the connection is broke. If you need to take apart the 48 pin connector it can be taken apart by using a 10mm socket to unscrew the bolt that holds that together.

 

The PCM Computer does not supply power to the injectors.
The Power comes from the Power relays red wire.
He is supplies power (jumping) to the red wire to run the engine.
The two wires to the injectors from the computer are ground wires to fire the injectors.

 

ok. swapped harnesses from my old 5.0 to the truck and came back with the same results. one thing i did not know is that my coil has 12v on both terminals with the key on. not jumping any wires. but if i jump that tan/yellow wire to the negative side of the coil, the truck will start lol. i know the negative side is for the tach, but not in my case for some reason.

 

On a diagram for an 86-95 SD I see a VPWR wire going from pin 37 & pin 57 (both of these are connected) then also attached to the relay you mentioned. It looks like all of these are connected in parallel. Are you saying the VPWR is a trigger to close the relay?