How’s this for FN weird?

[Connor M]

Alright riddle me this.

Truck 2 dies while running, won’t restart.
Swap the ficms between trucks 2 and 23.
Both trucks run fine with the other truck’s ficm.

Swap the ficms back between the two trucks and truck 2 won’t start.

23 had a tuned ficm, and truck 2 has an injector dying if that makes a difference.

 

[Zeb]

Is the tuned FICM also a 54 or 58 volt?

I have seen where a stock voltage FICM and injectors with stiction or weak solenoids will barely run, put a hotter FICM on it and they’ll run.

 

[Connor M]

Is the tuned FICM also a 54 or 58 volt?

I have seen where a stock voltage FICM and injectors with stiction or weak solenoids will barely run, put a hotter FICM on it and they’ll run.

Nope, afaik it’s a 48 but i can test it real quick.

 

[Connor M]

Is the tuned FICM also a 54 or 58 volt?

I have seen where a stock voltage FICM and injectors with stiction or weak solenoids will barely run, put a hotter FICM on it and they’ll run.

The other ficm shows 48.9 bit the one in the truck shows 47.5

 

[bismic]

Intermittent electrical issue and coincidence?

 

[Zeb]

The other ficm shows 48.9 bit the one in the truck shows 47.5

Well.......

I’ll relate this experience for whatever it might be worth.

I built a set of injectors for a guy, and he elected not to have new solenoids put on them. 2 weeks after he installed them it started having a dead miss on #7 when it got up to operating temperature.
He pulled all the injectors, sent them back, and I installed new solenoids on all 8 injectors. 2 days after he installed them the 2nd time....miss on #7 when warm. He put a new Motorcraft injector harness.....no change. Miss on #7 as soon as it warmed up.
His son owned my old 6.0. I told him to swap FICM’s and see if the miss stayed with the truck, or the FICM.
Guess what......both trucks ran absolutely fine.....until my old truck chucked #3 rod out the side of the block 8 months later.

 

[Connor M]

Intermittent electrical issue and coincidence?

With the original ficm in it, it will turn over but won’t fire, if you shake the harness it will fire a little bit but won’t actually run

Cranked right up and runs with the other one in it

 

[Connor M]

Well.......



I’ll relate this experience for whatever it might be worth.



I built a set of injectors for a guy, and he elected not to have new solenoids put on them. 2 weeks after he installed them it started having a dead miss on #7 when it got up to operating temperature.

He pulled all the injectors, sent them back, and I installed new solenoids on all 8 injectors. 2 days after he installed them the 2nd time....miss on #7 when warm. He put a new Motorcraft injector harness.....no change. Miss on #7 as soon as it warmed up.

His son owned my old 6.0. I told him to swap FICM’s and see if the miss stayed with the truck, or the FICM.

Guess what......both trucks ran absolutely fine.....until my old truck chucked #3 rod out the side of the block 8 months later.

Wtf

I want to keep the original fitcm in the truck because the tuned one is mine. I’m gonna figure out what’s wrong with t2, and end with 23’s parts in it.

I’m going to figure out what’s causing the issue and fix it not just leave the ficms swapped

 

[sootie]

if you find out its a harness or plug issue, ive got a complete 05 6.0 here i would sell parts off if it would help out...

I dont have a ficm though

 

[Connor M]

if you find out its a harness or plug issue, ive got a complete 05 6.0 here i would sell parts off if it would help out...

I dont have a ficm though

I put a third ficm in it and it won’t idle but cranks up and drives alright.
Throws a code for the cps but it’s brand new. Going to try and isolate that and then see what’s up.

It cant be a harness because that ficms been in and out a few time and it won’t run with that ficm. But that ficm runs another truck. Really scratching my head.

 

[Connor M]

Ficm from a truck with a vgt issue (as it was described to me by another mechanic here) was out in.

Now the truck won’t idle, and it has the same issue the first truck does. Drove it (carefully) to my buddys and did a contribution test.

The way i read this I need two injectors, but i don’t know anything about how they read other than negative is bad.

But for the vgt issue, does the ficm control vgt? Run the vgt test and it looks like the vanes are staying at 50% and choking the truck out. MAP doesn’t change on the vgt test till 50-60 percent anyway. Unplug it and the truck revs up and idles.
That’s the same symptoms as the other truck apparently.

 

[ghohouston]

You getting the f.i.c.m. connectors fully seated?

 

[Connor M]

You getting the f.i.c.m. connectors fully seated?

Yep. All the way on. Pins are good too.

 

[TooManyToys]

SWAG Warning

I wonder if one injector harness has a slightly compromised shielding and one FICM's circuitry is more prone to EMF.

I know some HAM operators that say the 7.3L was a nightmare for EMF compared to the 6.0. Some HAM operators have EMF meters and if you know one, sweeping the two trucks might show something.

Down that path, does the problem truck have the injector harness properly grounded to the intake manifold? That's the shielding ground.

Just SWAGing.

 

[Connor M]

SWAG Warning



I wonder if one injector harness has a slightly compromised shielding and one FICM's circuitry is more prone to EMF.



I know some HAM operators that say the 7.3L was a nightmare for EMF compared to the 6.0. Some HAM operators have EMF meters and if you know one, sweeping the two trucks might show something.



Down that path, does the problem truck have the injector harness properly grounded to the intake manifold? That's the shielding ground.



Just SWAGing.

That’s entirely possible, Not much else makes sense. I’ll have to check the ground today.

Right now, I have a reman ficm coming if nothing else works.