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SES, loss of power, black smoke

Bernie

Bernie

Amateur Radio Operator - KJ4VOV
Messages
303
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13
Location
Fredericksburg, VA
So, as some of you know, the wife and I are in the process of moving from Fredericksburg, VA to Anchorage, AK. Part of the preps for that involved me driving up to Buena, NJ Friday night to pick up a new trailer (6x12 SA enclosed) to haul stuff up there in. Going up the truck ran well, but not quite the way it usually runs. Seemed a little weak on power at times. Coming back with the trailer though I got about 100 miles and started loosing power and had the SES come on. The truck'd cruise okay once it got up to speed, but getting there took forever and involved quite a bit of black smoke. Not "rolling coal" levels, but this has always been a clean running truck. Took forever to get it home like that but I finally made it late last night. Still haven't even unhooked the trailer, just left it attached and parked on my driveway.

Once I've had enough coffee and pain pills to ease the aches from the drive I plan to go see what's up with the truck. I don't have a scan tool, so can't pull the code(s), but my thought process is running along the lines of either a bad injector, injector pump problem, or fuel flow problem, and here's my reasoning: the black smoke tells me I've got a lot of unburned fuel, and the most likely cause of that is bad spray pattern due to bad injector or an injector pump not having enough pressure. Working with that assumption I'm starting with the simplest thing first. It's overdue (really overdue - like 10k miles overdue, because I forgot :shame:) for a fuel filter, so I'm starting with that. I have a spare behind the seat so I'll pop that in and see if it helps. If not, then he goes to a local shop Monday for diagnostics. I'm really hoping it's not the pump though, as that's an expense we could do without right now, and might be enough to tip things in favor of selling the truck.

(Truck's a '99 GMC C3500, 6.5 TD with 112k on the clock. Injectors were replaced at about 104k. PMD is remote mounted)
 
Your on the right track so far, look in the FAQ section, there is a way to pull codes without a scanner me thinks...

Bad fuel
filter
screen in the filter canister
injectors

check the codes first, could be as simple as a switch causing this...
 
Sounds like low boost to me. Without boost you are going to get everything you described. The black smoke and low on power is most likely excess fuel from not enough air going into the engine. An injector or pump issue would normally show itself all the time, not just under load.
 
Yup he above about air flow nailed it. Too little fuel can not cause black smoke. Only thing in the fuel system causing black smoke is a bad injector dumping too much fuel. That also cause a VERY noticeable knock.

Do you have a boost gauge? Take out the air filter and knock the dust out if you don't have a new one on you before your test drive to check boost. Don't bother with the fuel filter yet until you know you're getting the air.
 
Air filter is a new (under 5,000 miles on it) extended life filter from Amsoil. I forget the part number now but supposed to be rated for 100k. I'll pull it and check anyway though.

Changed the fuel filter which seemed fine, even given I'd let it go far too long. Nothing at all like the totally black one I pulled when I bought the truck with 66k on it.

When the injectors were changed by my favorite local shop I asked what his opinion of the turbo was and he showed me, it was "like new". Clean, quiet bearings, said it looked in better shape than most he's seen. Doesn't rule out a failure though. Unfortunately, no boost gauge handy, so nothing I can do there except let my mechanic check it. One new clue though... the SES comes on when you turn the key, like all the other indicators, then goes off and stays off a bit, then comes back on and stays on, even before trying to start it. I'll have to see the FAQ and find out how to pull the code.
 
Another clue... Fuel mileage had been steadily dropping before the injector change, but improved after, just not as much as I hoped. New. less aggressive tread tires helped there also, and it steadied out at 11.5 mpg. On the trip out to get the trailer it dropped to just a tiny bit over 10 mpg, on the way back it plummeted to the point I had to stop for fuel after 300 miles or I wasn't getting home, and it has twin tanks. Haven't crunched the numbers yet (can't find the receipt) but something like 38 gallons.
 
THEFERMANATOR said:
Sounds like low boost to me. Without boost you are going to get everything you described. The black smoke and low on power is most likely excess fuel from not enough air going into the engine. An injector or pump issue would normally show itself all the time, not just under load.
Click to expand...

My thought process ran along the lines of the IP not producing enough pressure, resulting in a weak "pop" on the injectors and poor fuel spray pattern. Can't claim that I thought that completely though though, since I was still working on my first cup of coffee.
 
This has vacuum pump or related boost control solenoid system written all over it. The vacuum system hold the wastegate shut. Vac pump failure is easy to test for vacuum off the pump engine running. Check all vacuum hoses for failure. Check the vac can off the turbo for leaking down with the proper leak tested used for HVAC doors etc. Then outright replace the electric control solenoid on driver's side of engine.
 
WarWagon said:
Then outright replace the electric control solenoid on driver's side of engine.
Click to expand...
This was a cab & chassis, so some things are not where you'd normally expect them. For example, alternator is on the passenger side and A/C compressor is on the driver's side. Planning on swapping it out tomorrow though before taking it to the shop.
 
I say not likely on the ip. If it is low on pressure, then your power drops off, and you never get any black smoke, because it doesn't have enough fuel.
 
wire you turbo waste gate shut and take it for a drive.......just don't hammer on it.......if it runs good it's in the vac/ boost control solenoid trouble
 
Bernie said:
This was a cab & chassis, so some things are not where you'd normally expect them. For example, alternator is on the passenger side and A/C compressor is on the driver's side. Planning on swapping it out tomorrow though before taking it to the shop.
Click to expand...
ALL 96+ 6.5's have the A/C and alternator like that. The boost control solenoid on ALL 6.5's is mounted over the drivers side valve cover intake manifold area near the rear of the engine above the glow plug relay.
 
heres a pic of a run of the mill 96 and up 6.5l truck engine.
trck65L65FB_01.gif
 
Am adding to the chorus regarding the boost.

Any generic OBD-II code reader should work and chances are good it will have a boost / vacuum related code.

At the risk of insulting a better expert than myself . . . Try the moving wastegate by hand at idle and it should fight you. If not, find the failed link (wastegate, solenoid, leak, etc . . .).
 
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