Today I took my '87 300SDL into Connecticut state emission testing. This is the first time I've failed with a diesel vehicle so I'm looking for suggestions. The test report reads:
Overall LMD Result Opacity Reading 21.6%. Opacity limit is 20%. If anyone has any suggestions and the order in which to try them I'd appreciate it. Lately my mileage has dropped from 30/31 down to 25/26 but I attributed that to winter fuel and weather conditions.

Try a fuel additive, or turn down the adjustment on your ALDA.

Simpler yet, pull the boost control line off of the ALDA and go through emissions that way.

Did you give it a good ol' Italian Tune-Up before the test? It could have been from residual soot in the exhaust system.

I'm presuming you have unburnt diesel smoke and not oil smoke.

Unburnt diesel smoke -

Replace the air filter.
Use a fuel additive like Power Service or Red Line.
Make sure the engine has been fully warmed up.
Try for a source of fresher fuel, like a truck stop.

Oil smoke -

Change the oil and filter just before the test.
Use STP Oil Treatment and 15W-40 conventional oil.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

21%?!? Wow, that is a lot of schmutz!!

Since the test is just looking for soot/particulates, an It. tune-up and clean filters and fuel is a really good idea. For reference, my 84 tested at 4 to 5%, so good numbers are achievable. I had mine done at the GMC dealer on rt 3 in Middletown, fresh oil in the crankcase and Power Service additive in the tank.

Run it up and down rt 9 like you stole it a few times. Take it out to the Berlin Turnpike and drag race some kid with a tomato can exhaust.

Good Luck
Jerry

when i failed the one time in ct , i had the valves adjusted and then it hardly read anything on the scale.

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

I can't believe the State of CT requires you to emission test diesels..what about all the big trucks that roll through your
state ??..

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2000 Ford 7.3 Powerstroke 4x4
2006 Mazda Tribute
1983 Black 300 D (donated to charity)
1993 Teal 300 D (160K) Sold
"I love the smell of burnt diesel fuel in the morning, it smells like ....VICTORY"

Semper Fidelis
USMC 1973-1976

21% is pretty bad. We really can't complain about the emissions programs treatment of diesels, it's a lot rougher on the gas engined cars. Anyway, valve adjustment, air filter and try it again to see if there is an improvement. If you are close to Ellington I'll take a look at it for you.

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83 M-B 300D- daily driver
83 240D gray market
2002 VW Jetta TDI- beater

I'll race ya! Sounds funny, but when was teh last time you changed your fuel filter. I was getting weak MPG's and they seem to have increased do to that.... Could also affect the emissions?

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#dieselFLEET
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'97 E300
'99 E300

All good advice here. My 82 300SD passed that same lame 20% opacity test a few years back so really you should pass next time with the advice of filter, redline, and maybe valves. Also get it good and hot, maybe premium diesel. At least you get one free retest

Is it a driveing test now or just at idle? Luckly mines got one of the old stickers on it, its good to June.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Thank you all for the advise........

My air filter should be OK just changed it last year. I probably am due for a fuel filter change, I'll do that before I retest. I think I'll just run the fuel down a bit add some redline and try to find some premium diesel. Does anyone know of a place in Ct that sells it?

For the member who asked, the emissions test is performed at 1800 rpms. Tomorrow I'll take a run up to New London on I-95 and see if I can blow out some carbon.

I plan on getting a re-test in about a week to 10 days. I'll post the result. Thanks for all the advise.

How could a fuel filter possibly cause and engine to make more emmissions? If it got plugged, wouldn't the engine emit less particulate matter since less fuel would be entering the combustion chambers?

P E H

I agree with the past posts.

1. Turn down the ALDA.
2. Disconnect the boost line to the ALDA,
3. Clean/replace yuor fuel and air filters.
4: Romp the ***** out of it on the highway before you take it in.

I would definitely try these other things first, BUT. . . I also have heard that running a tank of biodiesel will reduce particulates.

If those things don't work, you may want to consider your timing chain. If stretched enough, you will have lower mpg and increased smoking. Since you don't have to do valve adjustments like we poor OM617 guys, you may not have checked the stretch previously. If you're up in the 4-5 degree range, your timing could be sufficiently off to cause some of your problems.

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Tjohn

82 300 SD
77 450 SL (gone)

I'm with PEH. Bad fuel filters will reduce fuel, helping the problem rather than exacerbating it. On the other hand, bad air filter could be enriching the engine. You're getting too much fuel for some reason. This would also explain why your fuel economy has dropped. I'm not familiar with exactly how the systems on your engine works, but I would suspect that whatever mechanism enriches the fuel as turbo boost increases, is stuck in the wide open position.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13