4d55 Rough idle and Lots of white smoke

Hey everyone,

I am a new member though i have used this site a lot in the past but i am currently having problems with my 4d55 in my 1985 dodge d50

So some background on this engine it has 2500 miles on complete rebuild (new sleeves, pistons, bearing, ect..) minus the injectors and pump. The engine has a new 4d56 head with the recessed valves and 4d56 flat top pistons in it. For a turbo it has a garrett 2860rs bb turbo with a small intercooler plumbed in. It also has a snow water meth injection system on it.

So the problem is when i start it up after it sits for an hour or more it smokes white and has a rough idle like one cylinder is missing. It doesnt matter if it is 65 outside or 25. After i speed it up and clean it out it runs good and no more rough idle. The pickup was running and starting great with no issues at all until 3 days ago. I thought the problem could be due to a leaky injector because it was only one cylinder so i narrowed it down to injector number 4 and replaced it and that still did not fix the problem. I also checked the timing incase the belt skipped butt everything checked out. I also did a compression check and found that they are all the same right at 350 psi. I was not able to find what the compression is supposed to be on a 4d55 or 4d56 does anyone know what they are? Do you guys think that there could be something wrong with the injector pump? Any suggestions wound be great.

Hey man, did you ever figure this out? My truck has exactly the same mods minus the turbo but with a rebuilt pump and set of injectors and I cannot figure it out

Have you verified that there isn't an issue with the water/methanol injection system? It may be worth looking to make sure that it isn't spraying too much water on startup and quenching combustion in a cylinder

I cannot speak from experience, but several on here have recommended testing the glow plugs. They say that they should each be 1 ohm, or 2 ohm as a maximum.

I had air leaks upstream of the pump and it would barely get to 2k RPM and ran ultra rough. Swapping to a clear fuel line upstream of the pump or using a clear fuel filter can test for this, and finding the leaks is usually easy.

good luck,