2001 dodge ram cummins 24valve manuel 6 speed. Smoking black. injector 5 shows trouble, but the injector was changed. pump was also changed and still the same trouble. compression is good. truck only has 160000km. any ideas? could it be the computer? why only injector 5?

 

Bad injectors will cause a few different issues but generally a lot of black smoke is from a boost leak. Do you have any gauges to help understand whats going on?

 

is this black smoke at idle or driving, hard open throttle??
how did you determine #5 is bad? did the smoke clear up when you shut down the injector?
have you pulled codes? any codes during this event?

agree most time of super black smoke is lack of boost. just as KATOOM said if you have boost gauge what is it reading when driving? I would assume your egt's are high during driving if this is happening.

Check your entire air charge path. from turbo to hot side of intercooler,
the entire entercooler and cold side to intake horn..

you can make a boost leak tester for about 5$ with home depot parts.
google it, or look on u-tube.

I have seen some hidden leaks from an intercooler where it split. hard to hear at idle due to the fan and rotating stuff.

 

Check the driver's side lower boot for a cut. My sheetmetal was cutting into mine when I bought it.

A pair of linesman's pliers will bend it over nicely, then replace the boot if nec's...

 

the truck is 2 hrs away where it broke down. we are bringing it home this week and I will check what you all have mentioned and give you an update. thanx again.

 

You never said its broke down..... Is the excessive black smoke question about it not running? That might tell a different story.

 

The truck acted like a blown injector. The mechanic determined that it was injector 5 by isolating it. Changed it and it acted the same. Smoking black and even more when u throttle it. Also knocking from the excess fuel. So then he changed the pump. Same again. Figured it was a bad rebuilt pump. Changed again. Same. Checked the key way for timing and it was fine. He tested compression and did a leak down test. Still has excess fuel coming to injector 5.?????

 

I'm not sure what to tell you since I can only hope that your mechanic is knowledgeable and competent. What doesn't sound right is the fact that you and your mechanic feel that there's excess fuel running to cylinder 5. There's no reason this would happen since the VP doesn't function like that. The only reason cylinder 5 would ever see improper fuel supply is if the injector itself was bad.

Knocking is not a good thing either but understanding whether or not the knocking is coming from the cylinder or the bearing journal is something I would only hope your mechanic can figure out.

It just could be that you burned up the top of #5 piston and its affecting complete combustion. Cylinders 5 and 6 are the two which run the hottest and are the ones which generally are affected when EGT's are run too high.

 

Could he have a bad injector seat that is allowing bypass fuel past?

Not sure this is how they are set up but just a thought. I'd pull the injector and scope the cylinder if possible....

 

if your mechanic has a bore scope he can look in 5 and see if the piston top is toast.