I have a neighbor with a 7.3 also and he is having problems with his #8 cylinder. I believe the codes are glow plugs and injectors but im not sure. Anyway, he says the truck runs like crap from idle to about 45mph, so im guessing it runs rough at low rpms. He then said that when he guns it and is doing 80mph on the freeway it runs fine like nothing is wrong. Also, he has excessive black smoke and black out the whole street if he punches it from a light. even if the truck is all warmed up. Im thinking its the injector but i don't know if there is something that could be a simple fix. I've heard everything from glow plug relays, injector orings, and a whole new injector. All i know for sure as that the codes all pint to #8 cylinder.

 

Does he have any mods done on the truck?Has he checked fuel pressure at the fuel bowl?With all of the smoke it sounds like it is getting plenty of fuel.The lagging at low speeds has me.Just wonderring what the pressure is at idle and if a possible restriction in the tank.Has the .50 mod been done?
Just trying to help with the info you posted.

 

"all codes point to #8 cylinder"

Let me guess, cylinder contribution codes.

The truck needs more diagnosis as #8 will ALWAYS give a cylinder contribution test fault. Cylinder contribution tests ARE NOT "bad injector" tests.

Excess black smoke is caused by too little air to completely burn all of the fuel in the cylinder (inefficient combustion). If he's got a problem with an injector that is injecting too much fuel for some reason, it will feel like a miss (although it's the one cylinder that's actually "stronger" than the rest) and likely make nice puffs of black smoke (and often a "fuel knock"). If there's no noise, I certainly wouldn't count out the possibility of a leaky injector but it's not something I'd go chasing right off the bat.

Anything to decrease the air mass into the engine will cause sub-par performance and black smoke.

"Runs like crap"..... Low power or rough? You'll have to get that information out of him. Rough would be a weak cylinder (not necessarily a bad injector, but that's where diagnosis comes in). Low power (accompanied by black smoke) suggests that there is a boost or drive pressure leak. These will really show up under high load, low RPM conditions where boost is critical for performance.

Good luck.

 

Im going to go drive the truck myself and Ill post back up after. Hopefully i'll get the actual codes too.

 

Just drove the truck. Power wise its fine, its not sluggish at all. from 900rpm to 1900rpm it runs rough, truck shakes a little bit. 1900rpm and higher it runs fine and smooth. It doesn't poor smoke out but when you get on it it definitely smokes more than normal and it is BLACK smoke. The 50cent mod has been done and it has a full banks kit on it, chip exhaust brake, all that. The wierd thing is that at higher rpms the truck is perfect and runs like a bat outta hell. I couldn't get the codes.

 

Sounds like it's time to beg, borrow or rent a compression tester. Running perfect at higher rpms points to a possible compression issue.

 

So going off what I explained, does anyone know what could fix it starting from the easiest fix like a sensor to something major. My neighbor doesn't have the funds to just take it to a shop and is planning on fixing it in the driveway.

What will the compression tester tell me? There is a cracked piston or blown rings?

 

Compression test will help confirm how healthy the rings and cylinders are before your friend starts throwing parts at the engine. An oil analysis might show higher levels of fuel but that is not likely at this stage but I would look at the silicon level (which could be the root of the issue if you do find a compression issue.)

Other cheap and and easy things to check for are the turbo wheel for signs of damage, the turbo shaft for excessive play and oil in the ICP sensor.

I hope you find something simple and cheap to fix.

 

What were his exact codes. If it is an injector code, I would swap the solenoid pac off the top of the offending injector with another one to see if the code follows. this will confirm an electrical issue with an injector.

Barney