Engine/Transmission (1994 - 1998) Bad coke??

[Wasilla Rod]

I pulled and cleaned my stock injectors at the 120K mark. They were so coked they looked like nasty volcanoes with side vent boulder piles. I cleaned them very carefuly with fine steel wool and had them pop tested at my local diesel whizz bang guy and they were all right on. I was told however that you should not even touch the tips and that cleaning them was a mistake. She now idles smooth as ever and clean again. Is it normal to have them that coked and how is decoking normaly done? I am still stock except 15. 5 timing.

 

[CumminsPower98]

When I replaced my head gasket at 247k my injectors were very clean. All they had on them was a very thin layer of the normal buildup thats on everything in the combustion chamber. That was after driving over the road and towing for the last 125k at the time. I also run fuel additives quite a bit but not 100% of the time. If you do a lot of town driving and never get out and warm it up this could be the problem. I did a lot of town driving before I went over the road too. I know it would run a little smoother any time I took a little trip of say 200-300 miles. When I had my injectors out I cleaned them up with a little brass brush. I would be surprised if this hurt them at all. I can't answer how they clean them professionally.

 

[bmoeller]

A little bit of carbon on the tip is normal. Sounds like you had more. I think you need to hook up to a 10,000# trailer once in a while, and run the snot out of it, to get the EGTs up, and burn it off.

 

[Jim Fulmer]

Not for the light hearted but I just tore my 370's apart and cleaned them then reassembled them but did not have a pop pressure checker. You can use a can of break cleaner, a red tip and your hand over holding the nozzle to blow the cleaner through them and it works great. Then blow them out with air and shoot WD-40 for some lubrication before assy.



Jim

 

[Matthug]

Excessive idling, short trips, and crappy fuel can all cause a lot of build up on the tips. Just clean the tip with a wire wheel, any soot left in the holes will instantly blast out upon startup. Perhaps run a bottle of cleaner through the next tank just to help and make sure all the soot gets out.

Whenever my trucks starts idling a little rough I take it up this really steep and long hill by my house with 10-15 seconds of WOT in 5th and let the EGT's climb high (I run it until the truck tops out). This usually cleans it out real nice and it runs good again. This is more of a common problem with marine injectors though.