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Discussion Starter #1
Can an injection pump cause black smoke out the tail pipe?


I tried everything to get rid of the smoke on my 95 L56 6.5L and the only thing that worked was to turn the boost up to about 13 PSI.


I just had the head gaskets replaced and want to fix the problem right just in case it was the cause of them blowing.


If the IP can cause it, what part of it would it likely be?


ThanksEdited by: whatnot
 

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Well if turning up the boost cured the black smoke then I would say that you had too much fuel, so that would be in the injection pump, however there are a few factors when it comes to a '95 IP, they are electronic, and fuel dilivery is based on commands from the computer.


Here are a couple of simple things things to look at before condeming the IP.





Status of air filter, although if you are getting 13 PSI of boost it probably isn't too dirty?


Do you know what resistor you are running in your PMD?


What kind of mods if any have you done to the truck?


Where is the timing set at (TDC Offset)??
 

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Discussion Starter #3
I got the pump from a guy on TDP after he converted to a mechacical one. It didn't have many miles on it. He said that he didn't have any black smoke at all.


I have a '97 airbox with a K&N filter, 3-1/2" exhaust (no cat), non-egr intake manifold -1.94 TDC offset


I noticed today that if I hold the pedal to the floor, I can see a little black smoke out the tailpipe with the boost about 12 or 13 psi.


I haven't looked lately but last time I checked, the scan tool only showed a fuel rate around 65mm with a lot of smoke.


Would it work to raise the boost a little more to force the ecm to cut back the fuel under full throttle?
 

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Discussion Starter #4
I forgot to add that I replace the injectors with brand new ones and it didn't help the smoke any.
 

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Are you running an intercooler, with 13 PSI of boost I would be alittle worried, these engines stock can only handle around 10 PSI over the long run and not grenade themselves. I would be careful upping the boost anymore unless you have an intercooler installed. I am suprised that you already haven't set a 78 and the computer hasn't already shut down the fuel. If I remember right, and I do not have the book in front of me, 65 MM is a resistor value higher than a # 9 resistor. (But again, my memory isn't what it used to be, I can't even remember what my memory used to be
) That may be where the exsesive smoke is from, if you are not running an intercooler, than put one on it, up the boost a little more, and injoy the power.





Did you put your resistor in when you installed it on your truck, or did you reuse the one in the pump, if he went to mechanical it might have been becasue he maxed out his electronic IP for horse power, by placing an aftermarket #13 in it or something like that.
 

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Discussion Starter #6
I don't have and intercooler. A few PSI more boost doesen't really do much the the actual cylinder pressure does it? I thought the main problem with more boost is the intake air temperature getting too high.


Maybe the fuel wasn't that high, I will have to look again. I didn't ever change the resistor.


The computer doesen't set a code 78 because it doesen't know the boost is that high.


The guy I got the pump from converted to mechanical because it just went out of warranty and the truck stalled a couple times. (he had it replaced not too long before under warranty and didn't want to have any more problems with it)I kept the PMD that was on my old pump and never had it stall.


I just remembered that I did have a little black smoke before the old pump died. Do you think that it might be the PMD possibly?





Thanks
 

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i had my timming set at -1.94 as well, and found that i didnt get any more power, just more smoke at lower rpms, but i also have a large turbo, so i comes in later.


What are your EGTs?


does it smoke that bad? I have a chip that brings fuel at max to about 75mm3. i only get a little smoke untill the turbo spools-up.
 

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Discussion Starter #8
It was smoking just the same with the TCD set at -0.5


I have the pyro in the downpipe and it runs between 400 and 600 degrees usually but I hardly ever go past 3/4 throttle. If I put the boost back to stock, I have a hard time keping it under 850.


If I keep it floored, they will just keep climbing untill I let off. I don't know exactly how high it would go but I never went past the yellow section on my Isspro gauge.


The smoke isn't that bad with the higher boost but it does still smoke some with over 12 psi of boost and stock fuel as far as I know.
 

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I don't want to be the one to rain on your parade but 13 PSI on a stock 6.5 is too much, now if it is only peaking there once in a while you probably will be ok, if it runs that up long hills or if you pull down the road, and it rides up there, you won't have an engine much longer. Yes the cyclinder pressures do come up with more boost, if you have more air in there and the volume of the cyclinder doesn't change and the compression ratio doesn't change, then that extra air forces up the pressures. It will eventually explode a piston, I am quite frankly supprised your head gaskets have held. IT is not smart to run a STOCK (no intercooler, no low compression pistons) over 10 PSI of boost. You are correct that the intake temps rise with boost, and the reason your EGT's drop with more boost is there is more air in the cylinder therefore more out.
 

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Discussion Starter #10
It doesen't stay that high very long. I don't tow so it is just till I am up to speed.


If I only use about 1/2 throttle, it doesen't go much past 10psi which is about normal.


When driving at 80 mpg, the boost stays right around 10 or 11 while cruising.
 

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Am I missing something here? Why is it OK to run 13 psi with an intercooler but is not OK to run 13 psi without. 13 pound is 13 pounds whether it be 400 degree air or 10 degree air.
 

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Discussion Starter #12
I put the scan tool on it today and only get 60mm fuel rate.


If the pump is causing the smoke, is there anything that would tell me in the scan tool readings?


Also, I found a code 84 and a 99. I reset them and the 84 didn't come back but the 99 stayed even without starting the engine.
 

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13 psi is 13 psi but non-intercooled the temps get really out of control the more boost you run.
 

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I agree but what Cat3406 is saying is that without an intercooler,13 psi will explode a piston. My experience has been ( and I do not have an intercooler) is that the more boost I build, ( I run about 12-13 psi) the more power I get and the cooler my EGT run. With my stock wastegate I usually ran 7-8 psi boost. I had no problem pushing my EGT past 1000 degrees post turbo. Now after adding a Turbo-Master which keeps my boost at 12-13 I really have to work just to get it to 1000 degrees. My coolant temps always stay in the 200-210 degree range. I am completely stock other than Turbo-Master, High flow airfilter, chip and different exhaust.
 

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Also, I found a code 84 and a 99. I reset them and the 84 didn't come back but the 99 stayed even without starting the engine.





These two codes are APP codes. This module has three different circuts telling the ECM what to do for fuel.


What kind of exhaust are you running? I too had some black smoke untill I opened up the pipes and dumped the cat. I think the cat was plugging up causing too much back pressure. Just the pipes gave me 5 lbs. of boost and dropped 100 degs. on the pyro. The smoke is all but gone now.
 

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Discussion Starter #16
I have a kennedy 3.5" system with no cat and a K&N filter.


Are all the APP voltage readings supposed to be the same? 2,3 and 4 are all the same but 1 is about half as much.
 
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