Just bought a 97 Chevy dually with the much loved 6.5 :rolleyes: It had no power and lots of black smoke so my first thought was no boost, I was right, bad vacuum pump, several large exhaust leaks in the crossover and right side manifold to head surface. Also the turbo was very tight when spun by hand. Replaced pump, donut gaskets and manifold gasket, rebuilt the turbo and got it all back together and running. Now it it has loads of power and lots of black smoke, for a few miles, then the power drops and the smoke stops. The SES light does NOT come on. Previous owner said they replaced the injector pump recently, I can't verify other than to say the pump is clean and looks new.

I am assuming that the smoke is being caused by an over-fuel condition and maybe the PCM is de-fueling after a few miles. I have not had time to do much testing on it yet just got it back running and had time for one test drive this evening. If they used the wrong resistor or left the resistor out completely when they changed the pump/PMD could that cause this to happen?

The truck is also hard to start when cold or after it has been run for a while, if you just start it and let it run for a few minutes it starts back quickly. It doesn't seem to cycle the glow plugs long enough, the wait to start light only comes on for 2-3 seconds at most even when the truck is cold. Checked all the glow plugs and they test good with an ohm meter. They all have voltage coming to them, it just seems they aren't being energized long enough to heat up. I know that the grounds on these trucks can cause some weird things to happen would they cause all or some of the above problems? That's my next step to check and clean all the grounds.

Sorry for the long winded post, and thanks in advance for any help or advice you can give.

Sam.

P.S. My 95 is having issues as well, but I won't bother you with those till I get this one straightened out :)

Clean the grounds, then check for codes-the light doesn't always come on when codes are set.

Ben offers good advice many a "wierd" happening is cured by cleaning up grounds.

Go thru WG troubleshhting as well, when PCM loses control of WG it sets up for limp mode max 50mm fuel rate (resets when truck is shut off until situation happens again), your black smoke is normally an indicator of lack of boost.

PCM needs positve boost control, as de-boosting is tier 1 for self preservation, if boost is out of range and does not change per PCM request then tier 2, de-fuel kicks in. Sometimes but not always you get a check engine lite as well

As far as glows, you can have weak ones, that read good with a resistance check, but don't fully heat up when energized, only way to really know is to pull them and test with voltage and see how fast & how much they glow, tip only heating can cause extended cranks you are seeing

I spent some time cleaning grounds and battery terminals today and I think it took care of the starting problems.

I also spent some time driving with the scanner hooked up. Accelerating quickly it would run up to 2500 rpm strong and then fall flat from 2500-3500 with no smoke. If I let it shift on out into overdrive and lock the converter in then accelerate slowly 2500 rpm and about 70-75 mph with a 55mm fuel rate and about 6.5psi of boost is all it will do on flat ground even with my foot buried as deep as it would go. Max boost was around 8psi while accelerating. It would also set a code 236 if held at WOT for long.

Thanks,
Sam.

What was boost as shown on MAP sensor to PCM vs gauge, I had a MAP fail high once & I kept defueling/deboosting as a result high indicated boost to PCM, also what is your IAT reading

No gauge yet, should have it here this week. The boost readings I gave were from the PCM. I have another MAP laying around here some place I am going to change it and see if it makes a difference. I don't recall the IAT readings but I will check them and post back later.

I was playing around with my MT2500 and accidentally did a TDC relearn, boy I thought I had really broke something then. I followed the instructions to do a time set and TDC offset learn from the FAQ and it seems to be ok now, it set the offset to -1.8.

Thanks for the help
Sam.

TDC relearn with a MT2500??? what year cartridge, Time set maybe, but are you sure TDC offset learn is what you did ??? Hit time set active & truck went to a really lopey idle ???

I'm fighting my own turbo problems, but my cold start problems were really helped by using bosch glow plugs. Testing brands side by side was a real eye opener. I now have started as low as -30 after a weekend of sledding.

TDC relearn with a MT2500??? what year cartridge, Time set maybe, but are you sure TDC offset learn is what you did ??? Hit time set active & truck went to a really lopey idle ???

Sorry if I confused anyone. No I didn't do a TDC learn with the MT2500 specifically, I was checking the voltages on my accelerator pedal and inadvertently did what is described here (http://dieselplace.com/forum/showthread.php?t=2599), in the 98/99 timing setting thread. Only it never relearned a correct offset until I did a time set and went through the procedures in the thread. Once I did that it it ran rough for a few seconds then straightened itself out. BTW the offset went from -1.5 to -1.8 according to the MT2500 readings. In the 98/99 timing setting thread I referenced above you said that a Snap On MT2500 TDC display is incorrect vs. a Tech 2 tool a T2 -.25 to-.75 setting is -4.8 on a MT2500, a T2 -1.76 to -1.94 setting is displayed as -5.4 MT2500 only carries to 1 decimal place. Mine only shows one decimal but it doesn't seem to be as far out of whack as the numbers you posted. I will have to look at the cartridge tomorrow and get the exact version all I can remember is that it is a 96-2000 OBD-II cartridge.

To anyone out there reading this that hasn't done it yet, I wholeheartedly recommend reading through ALL of the FAQs listed here (http://dieselplace.com/forum/showthread.php?t=53309). It could save you from a small coronary episode when you do something silly.

Thanks for the help,
Sam.

I'm fighting my own turbo problems, but my cold start problems were really helped by using bosch glow plugs. Testing brands side by side was a real eye opener. I now have started as low as -30 after a weekend of sledding.

The glows are new, but I didn't install them, they were done just before I bought the truck. So I'm going to have to pull them and see what's up. Truck is still hard to start when cold even on 95 degree days like we have been seeing recently but at least it starts better hot after cleaning the battery terminals and engine grounds.

Thanks,
Sam.