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Discussion Starter #1
Alright, I've got a 94B 7.3l powerstroke that is giving me hell. Its my farm pickup, and last year it started running really rough right before harvest so it got parked and tools swapped to a different rig to get me through my busy season. Upon re-entry, the ol' gal refused to start.

This winter I've torn into it, seeking the suspected electrical issue. I started with the cheap stuff, tested all fuses, replaced the three sensors everyone suspects, replaced valvecover gaskets along with the harnesses that go from gasket to GP and injectors, along with GPs. My most recent experiment was to replace the engine wiring harness that goes to all the various sensors and valve cover gaskets. Still won't start.

My next thought is to throw a new injector control in there, but my experiments are starting to get expensive so I thought I'd see if anyone's had the same issues before sinking more money into a 27 year old pickup. Additional symptoms before parking; starting hard, running very rough (shaking whole cab), randomly stalling. Post-mortem symptoms include no smoke when turning over and heavy draw on batteries (drains them unless I disconnect).

I'm by no means an experienced mechanic so all thoughts are welcome.
 

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Do you know if this truck has ever had the PCM reflashed so that the OBD-II port under the dash is active? 94's did not have this port active and used the OBD-I under the hood (not a ton of diagnostic capability with this one). Many trucks got updated to later PCM programming when they were at the dealer for service, like mine which was updated to ALF4 program. There used to be a link on this site to the Powertrain Control and Emissions Diagnosis Manual for the OBD-I 94's, but when this site went to the new format, we lost all the very valuable information from the old site.

Is the CEL illuminated?
Does the Wait-to-Start light come on like normal?
Oil Level good?
Is the oil level in the HPOP Reservoir within 1/2" of the top?
Tach moving when cranking?
What's the fuel pressure when cranking? Minimum is 25 psi at a minimum crank speed of 100 rpm.

Where did the harness that you swapped come from? You can run into issues when swapping harnesses from/to early and late OBS PSDs due to differences in the connector pinouts.

Cheers!
 

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Discussion Starter #3
Do you know if this truck has ever had the PCM reflashed so that the OBD-II port under the dash is active? 94's did not have this port active and used the OBD-I under the hood (not a ton of diagnostic capability with this one). Many trucks got updated to later PCM programming when they were at the dealer for service, like mine which was updated to ALF4 program. There used to be a link on this site to the Powertrain Control and Emissions Diagnosis Manual for the OBD-I 94's, but when this site went to the new format, we lost all the very valuable information from the old site.

Is the CEL illuminated?
Does the Wait-to-Start light come on like normal?
Oil Level good?
Is the oil level in the HPOP Reservoir within 1/2" of the top?
Tach moving when cranking?
What's the fuel pressure when cranking? Minimum is 25 psi at a minimum crank speed of 100 rpm.

Where did the harness that you swapped come from? You can run into issues when swapping harnesses from/to early and late OBS PSDs due to differences in the connector pinouts.

Cheers!
I doubt if the PCM has been reflashed, truck was bought new in 94 and has spent its life on the farm, these are the first major issues we've had.
-Check engine light comes on when cranking
-WTS comes on like normal
-Oil level good, have not checked HPOP level
  • Tach moves when cranking
  • Have not checked fuel pressure, was only looking at electronics so far because of heavy draw on battery.
  • New harness was a Motorcraft part for a 94B powerstroke, although they warned me that fords site had my VIN outside that part #'s range. No replacement harness showed for my VIN, so I went with the next closest part.
 

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Call your local dealer and see if there are any outstanding recalls. If not the PCM may of been flashe when one of them was done.

There are two recalls that I can think of that it might of gotten taken in for. One was the air box bolts and the other was a cruse control one. With either one it may of been flashed.

Sent from my SM-J737V using Tapatalk
 

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Discussion Starter #5
Call your local dealer and see if there are any outstanding recalls. If not the PCM may of been flashe when one of them was done.

There are two recalls that I can think of that it might of gotten taken in for. One was the air box bolts and the other was a cruse control one. With either one it may of been flashed.

Sent from my SM-J737V using Tapatalk
We had the cruise control recall done I know for sure.
 

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The one for the air filter box replaced the screws that hold it together. The replacement ones are steel and have a slot in them I believe. I haven't looked at my stock box in over 20 years

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The original airbox lid bolts were plastic and had a square-drive. As bugman mentioned the replacements are steel with a slotted drive. They also replaced the lid in that recall as well. Cheers!
 

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They came out with the recall since the plastic bolts were not creating a good enough seal and dirt was getting past the seal of the air filter.

I believe that the recall came out in early 97.
 

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Here's the TSB (originally 96-22-11) that replaced the lid and bolts. Cheers!
 

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Thanks. But that says if the nuts aren't stripped, and there's no dust past the filter, to just put everything back the way it was. And it doesn't apply to '97s, so that makes it sound like these metal ones were OE on my truck.
 

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The later trucks got them from the factory. I actually got a recall notice on my 94 and they replaced the lid and nuts. Cheers!
 
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