Startup smoke/rough idle after valve adjustment - PeachParts Mercedes-Benz Forum

jcbri · #1 08-22-2006, 12:05 PM

OK, this is my first post after "listening" for a while, great forum!

So after a while of longing I finally got my first MB, 1985 300D. What a car! A little scary on eBay but I think its OK. There were, of course, no maintenance records on this beauty with 227,000 miles, but she seems in pretty good condition. One owner, garage kept, non-smoker, went to an auction and purchased by my seller who only had it long enough to eBay it, hence no records.

It started right up after 3-4 seconds of glow plug and idles very smooth without any vibration. After driving it a bit and not liking the lack of power and not shifting very well at all, I decided to perform some maintenance and discovery. Vacuum at the brake booster is 19 at idle. I adjusted the valves per spec INT .004" and EXH .014". I did a compression test after the adjustment and found as follows: #1 390, #2 380, #3 280, #4 380, #5 360. I "glowed" all the glow plugs briefly while the injectors were out and they all worked fine, then unplugged the wire from the relay to not heat glowplugs while cranking engine for testing. I replaced the air and fuel filters and put it all back together, using the old heat shields and injector return lines as I could not get new in a timely manner before my eagerness to see how well it was going to run. All of the valves were completely shut down without clearance before adjustment and the timing, when the marks were perfectly lined up, was at 3 degrees ATDC. The timing chain was very tight to the sprocket and there was no scoring on the cam lobes. Upon putting it back together bleeding the injectors the battery got weak so I charged it with my 6 amp charger for about a day. When I finished getting it together and fired it up----I noticed mega white exhaust smoke and boy, was it running ROUGH! There was noticeably more blow-by out the valve cover breather hole. It seemed to calm down after it had warmed up but still smokes a lot. I took it for a spin and it still runs without much improvement in power or shifting at lower speeds but seems to run a bit better at 60-70 mph. It still idles very rough when warm and still smokes. Also the battery dash light is on now when driving---the battery voltage is 12.5 volts off but 12.3 volts when at idle. Could this have happened, maybe fried the voltage regulator, with charging the battery?

I am very confident that the valves are adjusted right as I painstakingly checked them all a second time before buttoning up. I've noticed that the linkages need adjustment as the injection pump linkage does not contact the pump stop--its about a quarter inch short at full throttle. The EGR valve does not hold vacuum so I plugged the line and on test drive it maybe shifts better but can't really tell.

Can anyone offer some advice? I'm going to do a diesel purge and see if it helps. Can the pump be out of time? Can the #3 low compression be the culprit? Could having no clearance on the valves cause the engine to run smoother? I appreciate any input, sorry this got so lengthy.

Brian

resago · #2 08-22-2006, 12:19 PM

white smoke is coolant. does it smell sweet?
you probably have a bad gasket now that the valves are adjusted and creating higher pressures.

CAPT POUNDCAKE! · #3 08-22-2006, 12:40 PM

ROUGH IDLE WOULD BE DUE TO 100PSI DIFFERENCE IN COMPRESSION AT CLINDER #3....ID HAVE TO SEE THE SMOKE TO ACCURATELY MAKE A CALL, BUT IF IT IS TRULY WHITE, THAT COULD BE COOLANT

LACK OF POWER COUPLED WITH HARD OR LATE SHIFTING IS USUALLY A SIGN OF FEUL STARVATION......I.E CLOGGED STRAINER/FEUL FILTERS....GOOD LUCK!:fork_off:

1985 300SD Sady · #4 08-22-2006, 12:41 PM

Quote:

Originally Posted by CAPT POUNDCAKE!

ROUGH IDLE WOULD BE DUE TO 100PSI DIFFERENCE IN COMPRESSION AT CLINDER #3....ID HAVE TO SEE THE SMOKE TO ACCURATELY MAKE A CALL, BUT IF IT IS TRULY WHITE, THAT COULD BE COOLANT

LACK OF POWER COUPLED WITH HARD OR LATE SHIFTING IS USUALLY A SIGN OF FEUL STARVATION......I.E CLOGGED STRAINER/FEUL FILTERS....GOOD LUCK!:fork_off:

1985 300SD Sady · #5 08-22-2006, 12:42 PM

Quote:

Originally Posted by resago

white smoke is coolant. does it smell sweet?
you probably have a bad gasket now that the valves are adjusted and creating higher pressures.

That sounds right.

Do you see oil in your coolant bottle?

Have you lost any coolant?

jcbri · #6 08-22-2006, 01:42 PM

Thanks for the fast replies!

The smoke smells of diesel fuel, not sweet. I haven't driven it but 15 miles or so because of the battery/charging problem, the battery today shows 12.3 volts and runs at ilde at 12.09 volts. I'll install a new regulator and see if this gets better.

I ran it a while at lunch today, there is no oil in the reservoir or coolant in the oil. I'll cycle it through a few run/cooldown cycles to see if it looses coolant in the reservoir.

Another thing I noticed today....sitting in my driveway, when you give it half throttle or so it takes it a while (5-10 seconds) to "spool up" to hold a higher RPM. The smoke is not there as badly at 2K RPM as yesterday when its warmed up....could it just be starved for fuel and really carboned up in the engine? I'll check the tank strainer (filters already replaced) to see if this gets better.

Maybe it just needs a high speed freeway blow-out before tackling the shifting problems?

Thanks for your replies,
Brian

Johnhef · #7 08-22-2006, 01:51 PM

for battery light just double check your ground straps- they will cause the light to come one if loose.

check your line from the rear of the intake manifold to the overboost switch for clogs- the banjo bolt at the manifold clogs easily if its never been cleaned. If its clear, but the line is ripped or disconnected it can make yo uthink you have all kinds of problems. The car won't get out of its own way and may shift rough or not at all.

jcbri · #8 08-22-2006, 02:13 PM

Thanks, I'll check the connections, I might have bumped something loose when doing the valves.

I forgot to mention that I cleaned the banjo bolt a couple of weeks before this valve adjust project-it was about half clogged. At the same time I replaced the air filter, it was pretty gummed up dirty but there was no oil in the air cleaner---my thinking was that there was no blow-by, a good sign.

Thanks again,
Brian

Brian Carlton · #9 08-22-2006, 05:47 PM

Disconnect the injector line at #3 and allow the fuel to run out over the head. Run the engine on four cylinders for 10 minutes. It will shake like hell, but, that's not what we are interested in.

See if the white smoke disappears after 10 minutes at idle with #3 disconnected from fuel. If you can run the fuel into some type of container so it won't make a mess of the side of the engine.

If the white smoke disappears, then the low compression on #3 is the culprit.

resago · #10 08-22-2006, 07:12 PM

thats right. at truck pulls, its white smoke until the turbo spools up and creates enough pressure.

so low compression burn is white smoke also. since you said its not sweet...

well, you need to fix the #3 anyway.

SD Blue · #11 08-23-2006, 12:24 AM

Hmmm...........I noted that you reused the heat shields for your injectors. I believe they are for single use. But the main question is are you sure that you reinstalled them correctly?

markg612 · #12 08-23-2006, 01:11 AM

Ok, let's get down to business and quit with the coolant spooks. IF IT DIDN'T BLOW COOLANT BEFORE YOU WORKED ON IT, WHY WOULD IT AFTERWARDS! Diesels blow white smoke all day long and twice on Sunday if they aren't firing on all cylinders. It stinks really bad and burns your nose and eyes like there's no tomorrow. I may be cutting my throat, but there are some really sharp folks on that write in here, and then again, well, you get the idea.

I sounds like it ran week but fine before you started into the tune up except for the low power. Mr. C is really sharp cookie, I agree with him on the week cylinder as the book stipulates not a lot of intracylinder differential and 100PSI is a bunch, BUT, if it ran smooth but weak you monkeyed it up then there is another source to find. Thats the good news! DID YOU TORQUE YOUR INJECTORS BACK IN??? This is huge! if you over torque, it will squish the tips to tight against the heat shields and alter the release pressure of the injector! If you under torque, they leak. The heat shields really need renewal.

Personally, I would get some new shields and re-torque the injectors to specs, double check your valve work and give it a go.

If it misses and blows white at idle, it isn't firing on all 5 and/or you've got air, but based on:

"It started right up after 3-4 seconds of glow plug and idles very smooth without any vibration. After driving it a bit and not liking the lack of power and not shifting very well at all"

I would make the afore mentioned corrections and then make a bee line to the fuel filer, specifically the spinon and change it out pronto!

Good luck Stryker, we're all counting on you! (original Airplane movie quote)

#13 08-23-2006, 01:38 AM

If it didn't start doing this until AFTER you adjusted the valves, you need to recheck them. I wouldn't drive it much until the lash is rechecked and the jam-nuts checked that they are tight.

Whitish/grey smoke can be from incomplete combustion due to low compression (The air does not get hot enough to ignite all the fuel).