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  #1  
Old 10-13-2004, 09:41 PM
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Smoking 350 Sdl

I have a 91 350 SDL that I had the injectors rebuilt and balanced to within one bar. I reinstalled them with new washers taper down torqued to 60 lb. ft. I installed new OEM glow plugs, and I did all of this in an attempt to get rid of the smoking at cold start-up. I ordered today, a set of pressure valve washers and o-rings with the understanding that maybe one valve is applying too much pressure to one or more injectors ? The engine puts out GREAT power and is quiet above about 1300 RPM and is super smooth. It also has, what I think, is more knock at idle than another 3.5 that I listened to yesterday. The engine, when smoking at cold idle also is very rough. Any help here is much appreciated.

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  #2  
Old 10-13-2004, 10:01 PM
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Describe the smoke,. How much? When does the engine do it and for how long? What color? Some smoke at startup is perfectly normal, more so now that it is getting colder in some parts of the country.
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  #3  
Old 10-13-2004, 11:01 PM
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Smoke and rough running at idle is poopy glow plugs or late timing. If the pressure valve holder seals are leaking, it won't smoke, it will knock horribly and shake like crazy, with poor performance from little or no fuel delivery.

The 603 is a smoker cold -- run the glow plugs 15 sec or so after the lamp goes out to help, but it's gonna smoke stone cold no matter what from poor cold combustion. Should smooth out in a few seconds, although mine will sometimes kick for 20-30 sec near 0 degrees F. No power til the engine starts to warm up either.

If the idle is rough, replace the engine mounts and shocks, they are likely shot and will greatly increase the engine vibration.

Peter
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  #4  
Old 10-14-2004, 12:56 AM
bisric
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My 350SD had afterglow for approx 15 seconds with the original glow plug relay. I could always tell when the afterglow quit - the engine would start to shake and smoke. If I started it up and slowly drove away it would be just fine.

To solve this issue, I ordered a glow plug relay for a 1996 E300D which has the capability of a 60 second afterglow. When I replaced the relay, I removed the glow plug temp wire from the wiring harness and replaced it with a wire to a variable capacitor (from radio shack). The capacitor makes the car think that it is 30 degrees out and I get a long afterglow.

Starts like a champ, idles like a champ, does smoke like a champ and the engine definitely runs MUCH smoother when the afterglow stops.

I used an adjustable capacitor so I could adjust the glow period in the summer vs winter. Small price to pay but winters are so much nicer in it. PS, I don't adjust it. I'll just replace the glow plugs a little sooner.

The one catch with my approach is that the glow plug light stays on for a long period, where it used to be much quicker. On wamer winter days, I don't wait for the light to go off, because I know I have rigged it to be longer.....

I love afterglow. I have also retrofitted my 1978 300SD (w116) with a relay that has afterglow. I have great results with starting that too!!!
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  #5  
Old 10-14-2004, 12:31 PM
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The only problem with keeping the glow plugs on like in the newer 606's is that you will start burning them out. My original glowplugs were 17 years old when I changed them. A newer 606 is lucky to get 50k out of a set.
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  #6  
Old 10-14-2004, 12:33 PM
bisric
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When i changed the relay, I also changed the glowplugs that are designed for the afterglow functionality of the relay. Newer diesels that I have had lasted longer than 50k on glow plugs, but yes I will agree that there life is shorter.
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  #7  
Old 10-17-2004, 02:24 AM
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Is the temperature sensor behind the front license plate bracket connected to the glow plug relay ? Also is it in the circuit for the temp control in the cabin ? After I changed the injectors, the heater will not work ? I do not know if there is a vacuum circuit that controls it or what ?????
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  #8  
Old 10-17-2004, 04:14 AM
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The temp sensor behind the front plate only goes to the LCD temp display in the dash. The outside temp sensor for the ACC is along the firewall near the wiper motor. There is a cold engine cut-off temp sensor on the head but this delays high blower speed, not heat. It's so you don't get a full rush of cold air first thing in the morning.

Please be more specific about "the heater will not work." No air, no hot air, no hot air from the expected registers?

Sixto
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  #9  
Old 10-17-2004, 08:34 PM
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All 1990-up MB diesels have afterglow. The time may vary depending on model, but they all have it. The 603 is NOT a 'smoker when cold', nor does it lack significant power when cold. You DO need to let it glow MUCH longer than the idiot light says when it gets colder than, say, 50 or 40F outside or it WILL shake and smoke. (The light is much too optimistic.) Try counting to 10 or 15 after the light goes out before cranking. This is not necessary when warm. I would wonder about the IP timing, btw. If it's never been adjusted, it's probably 2+ degrees retarded. It shouldn't be very noisy below 1300rpm.

BTW - when temps get really cold, like 20F or below, you'll need to allow a good 20-30 seconds of pre-glow before attempting to start the engine. The colder it is, the longer you let it glow, ignoring the optimisic dash glow light...

On a side note, my old 1987 300D had no factory afterglow. I used the 50C temp switch from the tranny circuit (which I bypassed, since it caused a flare when the engine was colder than 50C) to make a 'poor man's afterglow' setup. When the engine temp is below 50C, it leaves the plugs on for the full 60 seconds (minus whatever time I pre-glowed). Above 50C, it turns them off after the engine starts, same as normal. Yeah, this will shorten plug life by probably 20-40%, but I think it's worth it. Next set of plugs I install will be afterglow rated to compensate. :p

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  #10  
Old 10-18-2004, 12:06 AM
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Dave:

We get some white smoke for a bit on both 603s -- not for long, but enough to see drifting past the car. Usually acompanied by rough idle for 20 sec or so, no more.

The 300D is VERY sluggish for the first half mile, and I don't push it. Normal after that.

This is typical behavior of diesels -- all of mine do this to some extent. The 220D would rattle terribly for that first half mile, then settle down. My brother's Jetta TDI is worse.

Peter
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  #11  
Old 10-18-2004, 12:17 AM
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I dunno, my 603 doesn't do that, at least above 50F or so on a cold start. (I don't often get to drive it from a cold start below ~50F where I live.) If the power delivery is normal (0-60 in spec), after 30-60 seconds of running, power is more than adequate to pull out onto a 55mph road and get up to speed briskly. Still sounds to me like you might need a little ALDA adjustment, unless you're talking about REALLY cold temps (sub-freezing.) My VW diesel is more cold blooded, it is down on power when cold (running less than 2-3 minutes), even in summer mornings.

The slight smoke is more or less normal. The shaking is NOT. Might not be a bad idea to check your glow plug resistance. I had some shake & smoke for the past 2 months, and discovered I had two dead plugs! It starts smooth as silk now that I replaced them. Wouldn't hurt to check motor mounts too. My dad's 87 was shaking but new mounts cured that. You could hear something rattle inside the old ones if you shook them in your hands, off the car! The new ones were nice & solid. You also might want to glow longer, if you're starting when the light turns off, or soon after.

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  #12  
Old 10-18-2004, 08:46 PM
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Sub freezing to -5 F.

VERY sluggish when it's around zero F. I let it idle a bit then drive slowly to let it warm up before getting heavy footed. It will loose temperature when it's really cold. There is a railroad crossing about half a mile from the house, I've gotten stuck there sometimes in the winter and watched the temp gauge slowly crawl down as I freeze.

No smoke at 50 F.

My brother lives outside Detroit MI -- my niece says there is lots of stinky smoke when he starts the TDI in the winter.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #13  
Old 10-19-2004, 12:05 PM
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My 603 at least doesn't seem to be botherd by the cold until it gets closer to freezing. This year so far I started it at 40 and it fired up no problem, I just waited for the light to out and cranked and it fired up like it was 90 out.

I am kind of looking forward to colder temps to see how she does!
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  #14  
Old 11-04-2004, 11:45 PM
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Thanks for all of the great info. The engine will smoke at idle even after a 12 mile warm up run in the morning, this thing just rips out on the open road, and gets incredible economy, but as soon as it has idled for just a few seconds, like a stop light, it starts smoking and I am turning off the heater quick before the smoke gets too bad in the cabin ! I have determined by using a long 3/8 extension against my ear that it is #4 that is nailing (very loud and obnoxous) , as the other injectors have a light rap by comparison. It has no oil use (15-40 Mobil 1). Being that I have have found that #4 is the noise maker (gone above 1200) from what I have read it sounds like the prechamber is suspect ? Can the IP timing affect only one cylinder ? I also noticed the other day as my daughter pulled away that I could see a puff of smoke as if it happened when that cylinder was firing, intermittent smoke puffs at about one second intervals until revs built. I am in Love with this machine as I am a firm believer that these are the finest automobiles ever built, and I am determined to make this nailing on one cyl., smoking situation get resolved. Thanks again for all help.
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  #15  
Old 11-04-2004, 11:58 PM
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The fan will operate at all engine temps, but you have to stop the car, shut it down and after a restart the hot air will come out and after about five minutes will slowly go back to cold air. I can repeat this shut down business as many times as I want and it will go to cold and never put out hot air again until a shut down has been done, and even then the air temp is only warm and the temp gauge is showing 80C ???????
Quote:
Originally Posted by sixto
The temp sensor behind the front plate only goes to the LCD temp display in the dash. The outside temp sensor for the ACC is along the firewall near the wiper motor. There is a cold engine cut-off temp sensor on the head but this delays high blower speed, not heat. It's so you don't get a full rush of cold air first thing in the morning.

Please be more specific about "the heater will not work." No air, no hot air, no hot air from the expected registers?

Sixto
95 S420
87 300SDL

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