Fuel Trim

[6.4 Stroker]

I recently plugged into my truck with auto enginuiety just to get an idea if how it works. I pulled up short term fuel trims and noticed number 8 was was -17.
Should I replace that injector?
Not really sure what's tolerable.
Any help is appreciated.

 

[kyle43335]

+/- 3-4 i believe is the max tolerance. Are you getting a code for that cylinder stating the computer is maxed out for correction?


Also to the aftermarket scanners always had a issue with falsely displaying that number 8 injector was bad, when it wasn't.
No. 8 is 1 of the injectors used for regen as well, and mainly the injector, cylinder, piston that get damaged, because the injectors hang open.

How's the truck run???

 

[DWhite]

On mine at idle I'm seeing 0 to -1 except for cylinder number to and I'm reading 4.

 

[6.4 Stroker]

+/- 3-4 i believe is the max tolerance. Are you getting a code for that cylinder stating the computer is maxed out for correction?


Also to the aftermarket scanners always had a issue with falsely displaying that number 8 injector was bad, when it wasn't.
No. 8 is 1 of the injectors used for regen as well, and mainly the injector, cylinder, piston that get damaged, because the injectors hang open.

How's the truck run???

Truck runs flawless, no skips or bad injector rattle.
The engine has about 15k miles on it so I would hope compression is good.
I guess I could always test it.

 

[Powerstroke Man 6.4]

How does these look?

268,000 miles original injectors.

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[DEEZUZ]

IIRC +or- 10 is the max spec?

 

[DEEZUZ]

Either or, your maxed out and it's making up for something. Either a hard parts problem or an injector that's finally clogged from debris in the fuel system.

Just wrapped up another fuel system job, ~$10k. 2 cylinders were maxed out and it had a slight stumble when hot.

 

[6.4 Stroker]

Thanks everyone for the help!
I tested compression, all were dead even.
My guess is my Auto Enginuiety is falsely displaying cylinder 8 as was mentioned.
Before I get too carried away, I think I'll put an IDS on it and see what it says.

 

[Powerstroke Man 6.4]

Thanks everyone for the help!
I tested compression, all were dead even.
My guess is my Auto Enginuiety is falsely displaying cylinder 8 as was mentioned.
Before I get too carried away, I think I'll put an IDS on it and see what it says.

On my AE/screen shots above my #8 injector actually looks better than all my other ones LOL.

 

[Powerstroke Man 6.4]

Will different tuning cause different fuel trims for each injector? Say if one one tune #8 can be -/+ X and then on a different tune can it be different?

 

[DWhite]

That's a good question. On mine they are all bouncing around from -2 to 2 and then number 2 cylinder says at 4 and never varied, much like the pictures of yours that you posted.

 

[kingranchstroker]

Interested to see if AE is correct or not. Been thinking bout hooking mine up to see how health my ol girl is

 

[kyle43335]

It is absolutely horrible at how far off the balance, and calibrations of these injectors are. Most companies cannot test injector operation to MAX rail pressure.


I started making phone calls to some of the suppliers i use, and asked them at what pressure they were testing to, and to my surprise 8500 psi was most common answer. That is off idle. So anything above those pressures, they are guessing the injector will preform at a favorable output.


I do want to note. I did not call any vendor on this board. So this is not mistaken as some kind of bull **** call out post. I just found this info very interesting. I am currently waiting on some calls, and emails back from some companies that can even do it. ( running a 6.4 injector to max rail is a problem for alot of builders apparently)

I have been watching alot of injectors in these 6.4s lately, and even the new injectors are off. Alot of new injectors in new motors to so that variable is out the window.

 

[Powerstroke Man 6.4]

Checked on my dually today at idle (#4 was -22 and #5 -11) while the others where in the range of -7-9 are these numbers fine? Whats going on with #4? no codes

 

[DEEZUZ]

I'd do a compression test. Hot and cold, if that checks out then take a fuel sample at the injector feed tube for #4. Basically catch the fuel in a black aerosol can cap. Look at it under light. You'll probably find tiny metal shavings. You might be do for a fuel system

 

[Powerstroke Man 6.4]

I'd do a compression test. Hot and cold, if that checks out then take a fuel sample at the injector feed tube for #4. Basically catch the fuel in a black aerosol can cap. Look at it under light. You'll probably find tiny metal shavings. You might be do for a fuel system

That's bad news LOL this truck on its 2nd fuel system ( all new injectors HPFP rails etc). (Changed the fuel sytem at 42,000 its got 92,000 on it now) change the fuel filters when I do oil changes and that's every 7K (OEM Filters). I also run diesel kleen every tank drain the separator every month.

 

[Delaware6.4]

Good ol' 6.4

 

[DEEZUZ]

That's bad news LOL this truck on its 2nd fuel system ( all new injectors HPFP rails etc). (Changed the fuel sytem at 42,000 its got 92,000 on it now) change the fuel filters when I do oil changes and that's every 7K (OEM Filters). I also run diesel kleen every tank drain the separator every month.

yikes... I am not sure what 'Diesel Kleen' is, but these trucks so require a good lubricity additive.

When the fuel system was replace, does that include flushing/cleaning of the tank, fuel lines, new fuel cooler, lift pump, secondary filter housing, return lines, check valve, etc???

Also, were the heads back flushed with the old injectors still in?

 

[Powerstroke Man 6.4]

yikes... I am not sure what 'Diesel Kleen' is, but these trucks so require a good lubricity additive.

When the fuel system was replace, does that include flushing/cleaning of the tank, fuel lines, new fuel cooler, lift pump, secondary filter housing, return lines, check valve, etc???


Also, were the heads back flushed with the old injectors still in?

yikes... I am not sure what 'Diesel Kleen' is, but these trucks so require a good lubricity additive.


Power service silver bottle

When the fuel system was replace, does that include flushing/cleaning of the tank, fuel lines, new fuel cooler, lift pump, secondary filter housing, return lines, check valve, etc???

Yup

Also, were the heads back flushed with the old injectors still in?

Yup

 

[SlowSmoke]

I would honestly only trust an IDS scanner to diagnose injection issues on 6.4s, also I use a leak down tester over a compression tester, much more accurate at finding cylinder compression issues. It will pick up something long before you have bad compression. I've seem scuffed walls still make pretty good compression and throw a leak down tester on and it shows right away. It is a lot more work to do, but IMO a better test. I would hold your hand over the oil fill while running, usually a bad hole will puff out there pretty noticeably.