Author Topic: Potential causes of rough idle and unburned fuel (Read 4006 times)

overdrivegear · « **on:** November 02, 2007, 10:25:41 am »

I just put on a completely new fuel system: new IP, new bosch fuel filter, and bosch reman injectors but I'm still having issues with a very rough idle and constant stream of white smoke from unburned fuel that still persists even at operating temperature (and very bad at cold start). I can't figure this one out, what are the potential causes of these symptoms? Should I take the fuel tank and fuel lines out to ensure no dirty/water ridden fuel is getting to the IP?

Black Smokin' Diesel · « **Reply #1 on:** November 02, 2007, 12:46:35 pm »

Timing could be off if you eyeballed it. They are very precise pumps and timing is very important.

subsonic · « **Reply #2 on:** November 02, 2007, 12:56:25 pm »

I did not see glow plugs in your list. Have you checked to see if all your brackets are tight ? Nothing worked loose?

rallydiesel · « **Reply #3 on:** November 02, 2007, 12:57:32 pm »

Sounds like it is timed a little retarded. Try moving the pump towards the engine a tiny bit and see if it helps.

overdrivegear · « **Reply #4 on:** November 02, 2007, 01:19:23 pm »

The pump is timed exactly right. I took the range of acceptable values according to the book and set it to the average. Do you suggest placing the timing at the high end, then the low end to see any difference?

rallydiesel · « **Reply #5 on:** November 02, 2007, 01:42:02 pm »

Yes, you could try that. Or even before trying that, does the smoke decrease and idle smooth out with the cold start lever pulled out?

overdrivegear · « **Reply #6 on:** November 04, 2007, 08:28:52 am »

Quote from: "rallydiesel"

Yes, you could try that. Or even before trying that, does the smoke decrease and idle smooth out with the cold start lever pulled out?

The cold start valve actuated makes it slightly worse. I'm under the presumption that my IP was rebuilt correctly but if it wasn't, I would not believe there would be any 'half-way' working. Either it would work as it should or it would not. Could water from a leaking headgasket cause rough idle and white smoke from unburned fuel? Or perhaps water that was in the fuel tank?

rallydiesel · « **Reply #7 on:** November 04, 2007, 10:02:36 am »

Ok, so definitely not timing or pump related. You should check your compression. You may have poor compression in one cylinder that is not allowing full combustion in that cylinder.

Vincent Waldon · « **Reply #8 on:** November 04, 2007, 11:08:31 am »

Your timing can go at least to .95mm... some will take it out to 1.00mm (assuming it's a normally aspirated bunny).

I'd strongly recommend both a warm *and* cold compression test at this point particularly if you're convinced all the glow plugs are firing. There can be a big difference between the two numbers, and it sounds like you have way more unburnt fuel when the engine is cold.

You used brand new heat shields when you installed your new injectors right ?