From the '96 Powertrain manual - this is in the 'Description and Operation' section of "03-04B Fuel Charging and Controls, 5.0L and 5.8L Engines" (but this text does not occur at the same spot in 03-04A, the 4.9L chapter):
"If at any time, the PCM malfunctions, or the battery voltage drops to an abnormal level, fuel injection will occur for all cylinders simultaneously once every two revolutions of the crankshaft."

 

Well, the day is wasted if you don't learn something new and that will do it for me today. Pretty sure the strategy would hold for the 4.9 as well as the V8 engines.

Still, if this condition were to occur, you would have to have a processor capable of counting 2 revolutions as well as fire the injectors and you would have to have a pressurized fuel rail. That would, at minimum require a +5V supply as well as functioning fuel pump control. So, it is quite safe to make the assumption that the PCM is at least partially functional and it would be quite unlikely that you would have lost the internal +5V supply. Basic troubleshooting 99.9% satisfied. Now, on to why the PCM will not provide the active low required to operate the fuel pump relay.

Just another thought on the inability to read codes. Possibly a faulty scan tool? Worth checking even if it is a long shot.

 

I recently had a similar symptom. In my case the fuel pump was slowly dying but not dead. The only way the engine would start was if I gave the fuel pump a head start by manually activating it to build pressure for 10 seconds and only then would it supply enough fuel to start the engine.

While your issue seems to be more complex, I thought I'd at least throw my experience out there. A new fuel pump assembly solved it for me.

 

I don't mean to muddy the water here- take this with a grain of salt.

In my experience, reman PCMs from parts stores are at best a crap shoot these days. My original PCM quit activating the fuel pump too. Albeit a '94, it isn't drastically different from a '96 in its basic operation...

Subsequent numbers matching PCMs from the local NAPA store (whom I discovered gets their PCMs remanufactured from the same place every other local store does) didn't fix my issue.

What finally did fix my problem was an old Ford Reman PCM. I know your problem might be different. I don't know what's wrong with your truck. All I'm getting at is don't assume the replacement PCMs are good just because they have a shiny new coat of paint on 'em.

Check out what I went through in My First Thread.

 

I have not worked with many OBD2 PCM with EEC-V system.
I try to only work with the older OBD-1 EEC-IV stuff.
But when you buy a PCM for this newer EEC-V OBD-2 system don't they have to be flashed at the Ford Dealer before they will work right?

 

... a witch:

 

<< But when you buy a PCM for this newer EEC-V OBD-2 system don't they have to be flashed at the Ford Dealer before they will work right? >>

Curiously, some do need to be programmed, while others claim to be pre-programmed when delivered.

I have a Cardone 786398 and I was told by Steve at their customer service number that this part comes pre-programmed.

DPDISXR4ti, thanks for the suggestion. Both fuel pumps are new and verified to be working.

​​​​​​​Thanks again, y'all.

 

Just a quick update for anyone who might be searching for a similar problem.

I took my truck to a local shop run by a former Ford dealership tech, and they discovered that the PIP signal was stable, but at only 8 volts with the harness to the distributor plugged in. After unplugging components one at a time, they found that my new black plastic DPFE sensor had a short between 2 terminals. Swapped it for my old original metal one and everything woke up.

It's running really smoothly now, but they told me that the harmonic balancer ring had shifted and that they attempted to make a new timing mark. It runs sluggishly, as though it does not have enough ignition advance.

But, at least it runs.

Thanks to everyone who shared their experience with me.

-Jack (sluggish but running in Central Texas)

 

Well, that's one that I never would have figured out! Take good care of that tech. There aren't many left that have real diagnostic skills.

 

Great find!

 

GET BACK HERE!

YOU HAVE A 96 and you just mentioned PIP

ON my scan tool PIP goes On/Off it just cycles. IS THIS NORMAL.

 

The PIP signal is from the module in the distributor.

It's a 12v square wave oscillation that varies with engine RPM.

The PCM in my truck would not recognize the PIP signal, because it was dragged down to 8v by a short in the DPFE sensor.

The PIP signal is supposed to go on and off.

-Jack (now fully PIP-ed in Central Texas)

 

Relative to the above, I'm a little confused. Did the rubber break and the outer ring shifted but stuck in a new position? What's to stop it from shifter more? But let's say for a moment that it was (semi) permanently stuck in a new position... Couldn't the timing be set (correctly) accordingly?

Over the years I guess I've mostly ignored the discussions relating to the harmonic balancer, but now I'm wondering if it's something that should be proactively replaced. At this point they're all about 30 years old, and that is probably past their life expectancy.

 

Multiple issues with rubber that is so badly cracked and damaged:
- the balancer flys off, bounces around the engine bay, destroys your fan and radiator.
- is called balancer for a reason, if it rotates, your rotating assembly will be 'out of balance'

Yes, maintenance item, inspect and replace if necessary.

Why is the local shop run by a former Ford tech?
Did they not recommend replacing the harmonic balancer?
If the unbalanced engine starts to break other parts is the local shop now liable?

 

Aren't these 4.9L sixes internally balanced?

Also, why are the correct ODBII EGR valves $250, when the same part for a '95 ODBI is $50?

Just asking for a friend...

>8]