Lots of smoke - Altitude? - PeachParts Mercedes-Benz Forum

Fisherman · #1 06-10-2002, 06:28 PM

Did the requisite search oin altitude and found a lot of posts but nothing on my car...
1975 240D Pneumatic Governor
I noticed this last week when I drove from home at 3500' to the coast that going over the pass (5000') the car was blowing the usual cloud of black smoke while high revving pulling the hills in third. Got to the coast and while driving around (i.e. 3/4 throttle acceleration) noticed that the black smoke was a slight gray cloud not the usual "hit the throttle and look ma, no traffic behind me" thing I am kind of getting used to.
Then when driving the other day with the wife in the 240 back at 3200', I noticed that every time she accelerated at all there would be a cloud of black out the back of the car.
I know this is an age old question but how much smoke is too much?
I have been through the manual and cannot see the correct picture of my governor hence the possible altitude adjustment screw.
There is a hex head just in front of the breather to the pneumatic governor but nothing that sounds like the altitude adjuster.

Valves are set correctly, have not checked the delivery sytsem. Been running Lubro Moly additive with every tank.

Any thoughts folks?

psfred · #2 06-10-2002, 09:39 PM

I think there is a screw to set the max fuel adjustment -- I'll check with my buddy the German MB tech and find out exactly where it is.

I do not think that there is an altitude adjuster on that IP.

Causes of excess smoke (defined as visible smoke in the rear view mirror extending 5 or more feet behind the car at about 50 to 55 mph in third gear, accelerator floored) are incorrect injection timing, stuck injection timer, max fuel delivery to rich, low compression, and bad injectors.

The old-fashioned cheap and cheerful test for injector problems is to pump the accelerator with the car out of gear and running -- intermittant clouds of black smoke means sticking injectors. The proper way, is, of course, to remove them and have them tested.

Fuel will make a big difference, too -- some brands make more smoke than others, although fuel treatment usually reduces this problem.

Peter

Fisherman · #3 06-11-2002, 01:32 AM

Thanks Peter,
Intermittent clouds of black smoke... I got a good laugh on that one...:p
I can see a contrail kind of like a jet leaves for about a half mile behind me going up a grade.

Mechanic says he thought this motor was pretty good but we never got to the compression test or injector cleaning as I thought that was excessive dollars. I have a really hard time paying a mechanic more than I paid for the car.

If you can find out any info that would be great. Otherwise how hard is it for a novice deezel owner to pull and check the injectors? I'm a quick study and pretty good with wrenches but have never owned a diesel until this one.

dabenz · #4 06-11-2002, 04:52 PM

Some smoke isn't unusual when pulling a grade - daBenz will smoke hard before it quits pulling, then keeps smoking in third until the fuel is burned out.

The vacuum operated governor takes a little bit of thinking. The idea behind the mixture controller (the venturi upstream of the intake manifold) is to pull vacuum in the venturi at fast engine speeds, which pulls the diaphragm (the inside end of the vacuum box on the injector pump) against the spring in the vacuum box. The diaphragm is connected to the injector pump rack via a linkage that you can shim on the diaphragm side of the linkage, but you have to pull the vacuum box. And I hate pulling things apart that aren't broken.

Try this first: chase the vacuum line back to the mixture controller and pull it there. The line should hold vacuum. If not then either the line or the vacuum box is leaking. If the box then probably the diaphragm. If the line does hold vacuum then pull the air hose upstream of the mixture controller and look at the vacuum valve. This can get crudded up, especially if an oil bath air cleaner engine is run too fast or if the valve hasn't been looked at in a while.

I make sure the valve in the venturi is working, make sure the line and vacuum box are not leaking, and leave it at that. Then I make sure the butterfly valve in the venturi opens all the way when I roll the foot throttle linkage to the full throttle stop, and leave it at that. I can pull anything in third gear - a little smoke on the 7% grades at 45 mph. Last long road trip was 3600 mi to Seattle and back on two lanes and averaged 36 mpg with the 4sp manual, so I'm satisfied. But I'm also a bit fanatic about clean fuel, and that seems to keep the whole engine system working. Leaky injectors will smoke something - either out the tailpipe or wreck the glow plugs.

psfred · #5 06-12-2002, 09:59 PM

Lots of smoke can be several things, but if the car starts well cold, gets good milage, and doesn't use oil, the most likely are incorrect injection timing, a stuck injection timer, too much fuel, or bad injectors.

Don't take the governor apart on the injection pump -- it is fairly easy to get it un-connected from the pump rack, and when you start the car the engine will run away and throw a rod unless you very quickly loosen all the injector cap nuts -- there is enough fuel in the pump to destroy the engine.

I would check the chain stretch -- if it is very worn, you injection timing will be late and you will have excessive smoke and low power (the current state of the Volvo). It isn't too hard to get a new chain in (search related posts).

Peter

Fisherman · #6 06-13-2002, 07:41 PM

You bring up a good point in that my mileage is down to about 20 to 25 depending upon driving conditions.
I'm thinking timing or as someone suggested that maybe I have a fuel delivery problem.
I have been going through my manual and am having a hard time finding anything related to injector inspection and testing. I have the CD, does anyone know where this is on the disc?

dabenz · #7 06-14-2002, 12:44 AM

Fisherman,

Didn't find anything on the CD either. Injector testing is not typically a DIY job. Without getting too technical, think of the injector as a pressure actuated valve. Closed at low pressure from injector pump when the cylinder doesn't need fuel, then a two step opening process when the cylinder does need fuel. First step is the "crack", or a partial opening. Then full open. Both steps are at high pressure - in the neighborhood of 1500psi - and all injectors need to be operating within the same pressure range. Injector pump shops have the equipment to adjust the pressures and inspect the spray pattern at the same time, and prices are usually reasonable if you pull the nozzle holders and bring them in with the correct specs (that I don't have for your engine). Even new nozzles should be checked before installing. While a nozzle (part of the injector) can be cleaned at home with a wooden stick soaked in fuel, it's best to be shown in person as a fingerprint in the wrong place can ruin it. The CD does a good job explaining how to pull the nozzle holders and shows the parts that need to be replaced every time one is pulled.

Psfred, I hope I didn't induce confusion with my previous post. My vacuum checks and venturi butterfly check are both with the engine off. I do agree with not pulling the vacuum box unless the diaphragm is leaking. Unexposed parts seem to be the last to go.

Fisherman · #8 06-14-2002, 02:21 PM

Thanks for the insight.
I'll look around to see who I have locally that can check these out for me.
that and the fuel delivery thing might be the problems. There is a 12 mm bolt head on the top of my IP right in front of the breather and I can't find anything on that eoither on the CD. Might be the fuel delivery adjustment for max fuel but until I KNOW, I'm not messing wiht anything. It still runs just blows black at the kids that tailgate me...
I used to be one of them...

dabenz · #9 06-14-2002, 04:13 PM

Fisherman, I'll look at my pump for that 12mm bolt when I get home. This is when I wish I had a gee-whiz digital camera. I had to figure this stuff out with a 1966 Chilton's manual and the memory of that struggle is still embarassing.

TxBill, the puff when you let off may just be leaky injectors or a bit of carbon on the valves. A few hundred more miles on clean fuel may do the trick. Are you smoking out the oil fill cap on the valve cover? Also check the slotted connector for that gorilla switch fuel shut off cable. The fuel shutoff linkage should be loosy goosy in the slot when the gorilla switch is in the run position. I'd also check the vacuum box, line, and the vacuum valve in the mixture controller. Lose vacuum control and it goes rich, as the vacuum fights with a spring inside the vacuum box.

Both of you should post your injection pump numbers. My CD shows two different pumps for your engines. Seems like either Gillybenztech or JimSmith posted nozzle pressures for somebody else - hopefully they can do the same when we know what pump we're dealing with. The 240D didn't yet exist when my tech data manual was printed, but it does show pressures for my engine.

psfred · #10 06-14-2002, 09:07 PM

Guys:

I will check with Hans next week (I have to pick up more parts, of course!) to see where the max fuel delivery adjustment is on the older pumps. The adjustment on the vacuum governors may be at the flap in the intake -- I'll try to dig up the old manual and look. It may be called the max rpm adjustment -- you set the no-load engine speed to 4500-5000 rpm (fun with no tach and scary!).

For sure extra fuel gives more torque, but usually increases fuel consumption at bit and makes more smoke.

I've only seen one number of nozzle opening pressure for MB engines, but that doesn't mean there isn't some variation -- think it is 1700-1800 psi.

Peter

Fisherman · #11 06-19-2002, 12:56 AM

One other possible symptom???

I have noticed that my 75 240D tends to knock quite a bit from idle to about 1500 rpms (guessing) at medium acceleration and then it smoothes out and sounds like a tight little motor.

Could this knock be a possible symptom that is related to the smoking problem? Is it possible someone moved the pump timing up a bit? I seem to remember that this would also create a knock if too advanced. But in the diesel world does this mean smoke and knock both? BTW - I tried the little sitting in the driveway injector test and coming opn and off the throttle does prduce smoke. Not clouds but enough that I felt a little silly smoking up the old neighborhood.

BTW - Just changed out the rear brake lines today as they were cracked and with the MityVac to bleed the brakes it was a piece of cake. Took me all of an hour to change the rear brake lines and bleed all four wheels. The globs of gunk (probably water molecules) that came out of the rear calipers was pretty scary.

Bill,
If you see this, I goofed and didn't take any photos while doing the work but I can easily shoot some shots and do a write up. Do you need this one or do you have this project covered?

dabenz · #12 06-19-2002, 02:34 PM

Knock isn't unusual on a cold engine - ramp up the idle speed and let the pre-chambers warm up before driving, at least until the temperature gauge starts to move.

Knock on a warm engine: idle speed too low, leaky injectors, bad timing. Remember a diesel sounds like a diesel.

I'd do the fuel first. If you can do the brake lines then you can do the rubber fuel lines. Drain and biocide the tank while you're at it. Have spare fuel filters ready. Won't touch the diesel purge vs. ATF controversy after reading the archives (I'll follow the combined 90 yrs experience of two injector pump shops local to me). I also have a water separator and use Power Service DieselKleen continuously.

Then I'd double check the valve adjustment and measure the timing chain stretch while I'm in there.

I'd then set idle speed, after I've checked the governor vacuum system for leaks and operation, and making sure all the linkages are cleaned and lubed. I borrow an adjustable strobe light from work, but there are other alternatives out there.

Also: if an oil bath oil cleaner then check the oil and clean the filter, which is the basket in the housing, if the oil is dirty. Gas takes the paint off so I use a tub of soapy water and slosh the filter in it, slosh in clean water until no soap comes out, let dry overnight, then soak in oil before reinstalling. I use the cheapest 30W C-rated oil I can find for the summer months, 5-whatever C-rated oil for winter (the 5-whatever was for a 1970 pickup that I wish I still had). The cleaning drill is a good lesson to keep the oil in the housing clean.

Drive it for another 500-1000 mi and check results. For me clean fuel is the first trick to a diesel. Then patience for the system to clean itself.

THEN I'd look into adjusting timing and having injectors tested. The Bosch web site is www.boschusa.com. Click on auto parts, then diesel service (I think) to find shops where you live.

Good luck and let us know in 500-1000 mi.

dabenz · #13 06-19-2002, 02:42 PM

Had the Bosch web site wrong. www.boschusa.com. Click autoparts, diesel parts, then diesel fuel injection service. Click on a state to get a list of injector pump shops.

peterhardie · #14 06-19-2002, 04:06 PM

psfred:

I have excessive smoke (black trail on the highway in third) AND smoke at warm idle (light gray) AND smoke at start-up (mostly dark gray).
Coincidentally, the #3 cylinder seems to destroy glow plugs, cracking or burning the tips. I reamed before I installed the last replacement, my mechanic believing it may be arcing against the side. I still think fuel spray is off, there or somewhere else.

I have suspected fuel delivery, but what does the addition of smaked at startup signal?

I guess I'll have the timing checked and the injectors.

Peter
1985 300td

psfred · #15 06-19-2002, 10:05 PM

Peter:

Most likely you have a bad injector(s) -- they can spray almost sideways when the pintle gets chipped, and you can actually ruin a head by burning out the pre-chamber. You have to run it that way for a LONG time, but if you are burning glow plugs, I suspect a bad nozzle.

Testing is usually free at any diesel injection service -- there will be one somewhere near you. Just call. Nozzle replacement and pressure setting will run about $50 each.

There are two other causes of knock on diesels, at least MB diesels -- a loose chain from excessive stretch or a bad tensioner, worst on a warm engine at about 45 mph and a stuck injection timer that gives fast timing at low speeds. The later will cause knock and "snort" like a big truck with black smoke at low speed and excessive smoke at high speed if it isn't stuck at full advance.

I suspect the only way to check the centrifical timer is to remove it and check for free rotation against the springs. If one or more of the spring are broken or collapsed, you may have proper static timing but too much advance at low speed.

Peter

PS -- got the timing on the Volvo right at long last -- very little smoke and mucho power -- not as much as the 300D, but enough it is a pleasure to drive again!