Got a late 2004 6.0 that runs excellent. When it is cold (as in not running for half a day, not ambient temp) it dies as if the ignition gets turned off. You can start it right back up no problem. It has been slowly getting worse. You maybe have to start it back up 5-10 times before you can get going in the morning. Also you can hear a random click with ignition just in on position as if there is a connection issue in the dash and cuts ign in and out that I think may be the problem. I swapped all the relays to different spots to try them. I don't think it's wiring because it does it when cold then works when warm. Guy thinks plugging truck block heater may help it work better somewhat. New CMP, CKP, FICM, and it doesn't make a diff. So it's baffling to me. It's obviuosly electrical and works better when truck is warmed.

 

Just curious, I see you post a lot about different trucks, are you a repair shop or friends trucks? Just seemed like you had a truck with problems and then reading back, not the same truck, why the question.

 

Yes I do run a repair shop. But I get a few of these baffling trucks in that get me stumped.

 

I'd start at the PCM and make sure your connections are good and tight working toward the key.

 

I forgot to mention that Ford dealer already replaced the PCM

 

I'd monitor vRef power to the sensors, one may be shorting and killing it. Does the dash go out or flicker? Does the glow plug "wait to start" light come on when it dies? Inspect the wiring and connector for the fan clutch, connector can corrode, wiring can get chaffed on the intake manifold under fuel pressure regulator.

 

Wiring looks very good as far as I can see. No chaffing. It seems like it just cuts out as if you turn the key off for a miili-second and right back on. Just enough to kill the engine. I can hit the dash and wiggle wires all no diff. And only when truck hasn't warmed up yet.
How do you vRef the sensors and which sensors can kill the engine? I unplugged the ICP and accelerator pedal and it's the same. Also wiggled the ign. switch while running and it didn't act up from that.
Is there a thing like the GEM or the dash itself that can have something cold that will not connect and as it warms up it will go?

 

The glow plug light comes on for about a second after it dies.

 

The glow plug light coming on indicates the system completely dies and the computer thinks the switch was turned off. If memory serves, this indicates a periodic short in your VRef in the harness somewhere ... the proverbial electrical gremlin.

Others can chime in on where is the best place to start looking for the short.

 

You think it is a problem in the harness or a sensor/relay? It only does it cold and works good when up to operating temp.

 

Each sensor has a 5v reference voltage a common circuit to all IIRC any internal shost to any sensor will affect Vref to all.
Another spot that can shut you off like turning off the key is loss of sync. The engine will die immediatly because the FICM will not fire the injectors.
Check wireing from the cam and crank sensors.

 

One of 2 issues, vref short or back feeding voltage to the ficm or pcm.
Let me guess you get a p0603 or a p1000 that comes right back?

 

Try disconnecting the EBP sensor. They're known for causing a vref short if it's bad.

 

Just spitballing here, but only doing it cold suggest a sensor and not wiring. Temperature will affect sensors more than the wiring harness.

How that cheezit and money have provided input, I'm shutting up because they know 1000 times more than I.

 

Thanks for all the input. I'll check again for codes and try ebp unplug. Ford dealer already tried a new wire from CMP and they said it didn't help.