You might want to get a cheap coil when you get the ignition module. Eliminate the easy stuff before going to the PIP. Just a suggestion.

 

Great point. Much thanks. New ignition module is in & so far it's running better than ever. Hoping for the best. Thanks again.

 

I hope that was a Black ICM you put in your 1996.
If not take it out and go buy a black one.

 

yes, it's the black one. guess I lucked out there.
Also replaced the coil. Still not fixed.
I'm going to check thru some grounds, as a someone recommended earlier. I have a new pickup that I'll install if I can't find a ground problem.

So far:
1. Pro technician replaced main grounds because voltages out of spec.
Not sure which grounds or specs, but he said that part of it was fixed.
He said he couldn't do any more diagnostics without starting to swap parts.
He believed it could be a faulty connector because it seemed to not work as well after sitting in sun all day (expansion/contraction). It now randomly shows up any time of day.
2. Replaced PCM
3. Replaced PCM and fuel plum relays
4. Replaced ign mod
5. Replaced ign coil

Next steps:
1. Grounds (until I go completely insane...which won't take long...and yes, I know I should have checked this first.)
2. Distributor pickup

THANKS TO EVERYONE FOR THE MOTIVATION!

 

Could you elaborate on this one a little more Bill? You're talking about the 12v+ line that goes to the starter, yes? It sounds like you're saying that the the strands of wire in this cable are shorting against each other, which makes no sense, as clearly they're supposed to be touching each other and "shorting".

 

G101 (near batt) looks good. G100(near rad supt) was a mess.
Before cleanup it wasn't starting. After cleanup it did start.
When I turned the key to RUN, I heard the fuel pump, then a very brief pause, then the fuel pump again, but for about half the time as normal. Then the turned key to START & it started right up. (Recall that if I'm in a no start condition, when I eventually hear the buzz, the check eng light will properly go out when cranking.)

In a no start condition:
1. Turn key to RUN.
2. Hear fuel pump.
3. Turn key to START.
4. Check eng light does not go out, truck cranks but does not start.
5. Leave key in RUN for 2-10 minutes.
6. Listen for second fuel pump buzz (pretty sure that's what it is)
7. After buzz, it starts right up. (works same for both fuel pumps/tanks.

Hoping the ground fix continues to work. Thanks for the very specific advice. This is one I never would have discovered.

 

This only happens on the 5.0L engine as the wiring is ran different on the 4.9L, 5.8L and the 7.5L engines.

There is multiple wires in the starter (wiring) cable harness and not all are for the starter. This wiring harness runs right under the exhaust manifold and the wires inside get very hot and brittle.
I think what happens is a power wire or maybe a ground wire shorts to one of the O2 sensor wires and the computer then resets while running or when you try to start it.
As I said I never pulled the wiring harness out to see what is going on. I just unhooked the O2 sensor near the battery and ran new wires down the fender, through the frame and to the O2 sensor.
After I did that I had no more problems.
From reading on the internet this has happened to a lot of trucks with the 5.0L engine from 1992-1995 +???.

There will be six wires in this wiring cable harness in a 1995 F-series with a 5.0L with one HO2O sensor. You have a 1996 OBD2 system with two HO2O sensors. So I am guessing that your passenger side is the same. Where the wires run for the drivers side HO2O sensor I do not know but I guess they could do the same thing. I know the 5.8L wires run away from the engine on the drivers side.

 

Excellent advice. If/when it starts giving me trouble again, that's what I'll do next. Been working all morning since I cleaned up the G100 ground (near drv headlight and upper rad brkt).

And thanks to Brad for asking you to eleaborate, because it went right over my head.

 

Photos of the rewiring for the HO2O sensor:

Old HO2O sensor plug:


New Plug To HO2O sensor:


New Wiring to HO2O sensor:


/

 

Thanks Bill. Trying to sort that out now. My starter only has 2 wires coming from the battery (starter and solenoid). I do not see the 6-wire harness. My book shows 3 O2 sensors. The wires for the sensors in each manifold don't seem to be too close to the manifolds. The 4 wires from the driver side sensor do join up with a harness. Tracking down the third O2, which I think is after the cat. On your recommendation I'll run new positive wires to the suspect O2 sensors. This raises a couple more questions:
1. Could it be the O2 sensors? Probably faster to just run new wires first, then test if needed.
2. Could it be some other sensor, or it's associated wiring?
3. After the O2 sensors, should I start chasing grounds?
4. What are the chances of it being the distributor pickup?

How it behaved this morning:
1. Cleaned up the ground near the drv radiator bracket.
2. Ran really well all morning.
3. Let it sit for a couple of hours. Then no-start.

So far I have installed the following shiny new parts: PCM, ign mod, ig coil, relays.

Thanks!

 

Next to my battery I have 2 O2 sensor style plugs. They both come off of the main harness that come across the front of the truck over to the battery.
1. Blue one with 4 wires dead ends into a cap attached to the fender. No wires coming out.
2. Black one with 1 wire comes off the main harness, then goes to the alternator harness.

What if I just cut the power wire near the O2, then run a new wire to that point?

 

It does not sound like in 1996 they ran the O2 wires down the starter harness.
Yes I guess it could be another sensor doing this but I would think it would have to be a sensor or solenoid that had 12 Volts on it and not the 5 volt sensors.

Without rereading this whole thread have you checked for spark or fuel when it does not start?
I have had fuel pumps doing that before. They work sometimes and sometimes not.
If it was a sensor or a solenoid doing it and causing no spark I would think at that time you could unplug the computer or SPOUT and you would get spark back.

 

Thank you for all the time you spent on this one.
There is no spark in the no-start condition.
Fuel pressure at rail is always within spec in no-start condition.

I will unplug the SPOUT the next time I get a no-start to see if that helps.

My main question at this point, is....
Is now the time to replace the distributor pickup, or should I continue testing sensors and grounds?

 

In my opinion it is time to replace the distributor pickup. It sounds like you would replace the pickup in your current distributor, that would be the correct thing to do. If you get a REBUILT distributor you are very likely to have the same problem you have now. Most rebuilt distributors they must just shine them up and send them out for resale. A NEW distributor would be fine, but I doubt if you could find a NEW distributor.

 

X2 on post #29 above ^^^