Diesel Extremely ROUGH!!! when first started - PeachParts Mercedes-Benz Forum

777funk · #1 03-11-2007, 07:37 AM

Hi guys,
I have my third diesel so far that is SUPER rough when it's first started. I've checked the following and it's a 603 engine in a 124 body 300dt:
1.Glow plugs all read around .8 ohms
2.Just changed all the injector nozzles to Bosios (a little smoother when warm but that's it)
3.Don't need valves adjusted since it's a 603 with H/Valves

It runs fine once it warms up but at initial start, I have to give it a bunch of throttle just to get it started. Shouldn't be like this but where do I start?

Thanks,
Nick

btw it's 42 degrees F this morning.

777funk · #2 03-11-2007, 07:43 AM

btw, I forgot to mention that it SMOKES like Crazy on initial startup and I can smell a lot of unburnt diesel in the exaust. But once it starts firing as normal that all goes away.

All fuel spillover lines (soft lines) have been replaced.

Parrot of Doom · #3 03-11-2007, 08:00 AM

You're not running it on veg oil are you?

I can only think that its glow plugs or bad fuel. Valves can go out of adjustment if the timing chain is stretched, although not by much.

Your glow plugs might read ok, but are they receiving power? Check the terminals with a voltmeter before you start the engine up, the relay might be duff.

777funk · #4 03-11-2007, 08:19 AM

Relay is good as well. It's giving 12v to plugs. Not Veg oil (Yet!).

deuce · #5 03-11-2007, 11:19 AM

I've had the same issue for the last 3 months and have gone through a bunch with my mech. It all started with a 30K service and fuel seal replacement due to the new low-sulfur diesel. Tons of white smoke with diesel smell in it and running like I'd dropped a cylinder. I was also getting a strong exhaust smell in the cabin to the point that I had to run the charcoal filter to get it to go away. He ended up having the injectors rebuilt (they tested at low pressure) which fixed it a bit and made the car run great but after starting and left to idle for 2-3 minutes the white smoke stuttering would return. He made a "tweak" to the EGR valve and that seamed to fix the problem. Every now and then I'll get a whiff of exaust in the cabin but it's faint and goes away quickly. I also noticed that if I run RedLine Catalyst in the fuel the problem is non-existent so I'm wondering how much of this was attibutable to the new diesel blend.

jbach36 · #6 03-12-2007, 09:29 PM

I read on some previous posts that when they changed to the new Bozio nozzles, the car ran rough for the 1st 500 miles or so, then purred like a kitten. I don't know.

jeff

jshadows · #7 03-12-2007, 09:58 PM

Quote:

Originally Posted by jbach36

I read on some previous posts that when they changed to the new Bozio nozzles, the car ran rough for the 1st 500 miles or so, then purred like a kitten. I don't know.

jeff

yes, I can confirm that...ran worse than it did before I put the bosio's in...drove 1000 miles from NOLA to DC and ran sweet ever after.

deuce · #8 04-20-2007, 11:00 PM

Quote:

Originally Posted by Parrot of Doom

You're not running it on veg oil are you?

Well, the smoke and rough idle is back and I'm wondering if the reference in this quote is the culprit.

I had the same problems as the OP (as I'd posted earlier) but most of had been fixed by my mechanic (rebuilt injectors and adjusted the EGR) and all was running fine. I'd put B20 in it a few times since and the car ran like a champ. Then I went off the deepend. I've been wanting to try B100 for a while and found a local place where it was sold. I drove over and the place was a VW/MB repair shop with a loading dock that had a big vat of Bio sitting on it. I'd finished filling up ($2.68/gal

) when the guy told me the Bio was made from WVO. I got a bit nervous but figured I'd be fine. Well...I was wrong. Now when I start up in the AM and idle the car for a couple of minutes it begins to shudder, skip and pour out white smoke that smells like Wesson. The strange thing is that once I drive for a few miles the car smooths out and runs pretty well (although a bit sluggish). I do get a Wesson smell in the cabin sometimes and if I get out you can definitely smell the some unburnt fuel.

So, what have I destroyed? Is the engine toast or is it just hoses and seals? Any input is appreciated.

Cervan · #9 04-20-2007, 11:14 PM

oh god i can only immagine how bad this will be on unheated veg oil.....

deuce · #10 04-20-2007, 11:19 PM

Quote:

Originally Posted by Cervan

oh god i can only immagine how bad this will be on unheated veg oil.....

I'm guessing from your post this is not going to be pretty. It is supposed to be Biodiesel and not straight veggie oil. He said they use a flow control for their winter blend and it looked like a chemical process and not just a filtering process.

What are you thinking is dead?

Kuhlrover · #11 04-20-2007, 11:43 PM

It sounds to me like you have very low compression in one or two of your cylinders. It is obviously getting fuel because that is what is causing the white smoke. However the air in the cylinder is not getting hot enough to light the fuel.

How bad is the blow by when it is idling rough and when it is warm? Have you tested the cylinders for compression?

While is running rough, you can try cracking open each of the injector lines one at a time. By doing this you prevent the fuel from opening the injector. (It like removing the spark plug wire and a gasser motor.) If there is no change in the sound of the engine as fuel starts to weep from the injector connection, then that is the cylinder that is not firing. If you crack an injector line open and it makes it sound considerably worse then that is a working cylinder. Keep in mind that fuel is at a really high pressure. After you loosen the fitting wrap a rag around the top of the injector so you don't accidently shoot diesel fuel in your eye and all over the motor.

TimK

Marcb · #12 04-21-2007, 01:41 AM

Are you trying to start it right after the light goes out or are you listening for the relay to click off? The 603 loves extra glow time and it makes a huge difference! You might give it a try and see if some extra glow time helps.

deuce · #13 04-21-2007, 12:56 PM

Right after the light goes out. I'll try some extra time and see what happens.

Marcb · #14 04-21-2007, 06:26 PM

Quote:

Originally Posted by deuce

Right after the light goes out. I'll try some extra time and see what happens.

Our 300D is night and day different when you wait until the relay clicks off. Cold starts when the light goes out are smoky and not nearly as smooth. Let us know if it helps...

quinny · #15 04-25-2007, 05:09 PM

My 87 300tdt wagon has been doing the same and it's getting worse. Longer glow helps. I'd like to check my glowplugs with a multimeter. Could anyone offer some help on how to do this?