Smoking, carboning, poor cold off idle with little to no blowby. What could it be? - PeachParts Mercedes-Benz Forum

BoostnBenz · #1 02-28-2004, 12:54 PM

Hi all,
Ever since I bought the 83 a year and a half ago it has ran somewhat odd. It was really laggy off the line before but it was the quietest diesel after about 1500rpms. So in hopes of getting the off the line performance up to par I changed the timing chain but was dissapointed that I gained nothing. Quite oddly the wear was about 5.5* before and 4* after, perhaps I should buy the 2* woodruff keys?! As time is going on the smoke is getting worse. So from there I figured maybe the injectors weren't clean so I ran some diesel purge in, not much gain. I took the injectors apart and verified they were totally clean, that is everywhere but where they are in the PCC. The motor has since became louder but I don't hear any nailing unless I gun it and the instant the motor is catching up I've heard it before.

By now the smoke was bad enough I could see it at cruise speeds at nightime. So I figured the next step would be to adjust the timing. I bought the IP camshaft lock tool and set it 1* advanced, the off the line performance increased dramtically but it still is no where as nimble as my 84 300D was. The smoke did seem to fall off noticeably at this point but still not right. Lately it has been acting up a little with running near 100*C (with heat off) but after swapping thermostats it seems to be at a reasonable 90*C.

Just last night I noticed something else I find disturbing it seems as if when it starts it doesn't just run binary (off or on) like it did before instead it is kind of a half starting half running start. I suspected the GPs were wearing out, all are 1.0ohms or below. However, they are all covered in a pretty thick layer of carbon. Well last night (about 30*F, no heater) I gave the pedal just a little nudge like normal just to stabilize the idle. Everything was running like normal, but just to see what it'd do I gave it a bit more. The smoke came hurling out even worse, as I pushed the pedal down further the motor started bogging down again, it never went past 1200rpms and started falling back down as it bogged. Like I mentioned before it doesn't just smoke cold it smokes warm and as far as I know while driving as well. The mileage is still decent but the lowest it has ever been (26-30mpg). Most of the driving is at about 60mph with a good mix of stop and go.

I have most of the glow plugs out right now and am in the middle of doing a compression test (need an fitting for the adapter) but I doubt the numbers will be very low due to the lack of blowby and oil consumption.

So what do you think I should try? I was somewhat thinking of new injector nozzles but the probability that all 5 injectors are bad at once is near impossible. All 5 cylinders seem equally carboned up. I'm thinking about putting a 2* woodruff key on the camshaft to rule that out just in case the 4* retarded cams and 1* advanced (14 or 15*ATDC) IP is causing it.

Thanks in advance.

#2 02-28-2004, 01:29 PM

Hi Jeff.

Did you check the banjo bolt on the
intake manifold?
Clean out the carbon of it and the hose
running from it.
It sounds like the engine is seeing an
overboost condition all the time.

I tought the timing had to be 24*before TDC.
I could be wrong on this.

Louis.

DieselAddict · #3 02-28-2004, 01:36 PM

You didn't mention valve adjustment so I'm not sure if you've done it. Misadjusted valves will definitely give you smoke and poor cold running. I'd also take a look at the governor idle pin (or rack dampener pin). If it's all the way in it may cause surging and other signs of fuel starvation. It should be in only as much as is needed to make the engine run smooth when fully warmed up.

BoostnBenz · #4 02-28-2004, 02:01 PM

Yes that line and those bolts are all clear. 24BTDC is using the other methods (drip & bubble), the 14ATDC is for the locking tool method.

I didn't adjust the valves just once but twice (in 5k miles) to be certain that they are adjusted perfectly. I upgraded to the gold damper pin and it is set such that it is barely in at all, the least amount inward I can have without the car rocking like mad from side to side.

shane83SD · #5 02-28-2004, 09:43 PM

Hi Jeff,

Is it a turbo? If so, I would hook up a boost gage and observe the boost pressure. Seems like it is running with too much fuel.

Are the tips of the injectors dry when you pull it?

Do you just fill up? Maybe it is a bad batch of fuel for the recent trouble.

#6 02-28-2004, 09:49 PM

Boostnbenz, just for clairification, is it white smoke that you're seeing when it's running roughly at idle?

If so, unburned fuel. The only think I can think of is compression... but you say you have no blowby.

lietuviai · #7 02-28-2004, 10:21 PM

BoostnBenz's problem sounds a bit like the problem I've got except once it's warmed up it seems to run OK except for the one noisy injector I've got. I think that might be the root of my problem but I've got to wait until I'm able to get some good injectors for a reasonable price. It seems everyone except TomJ wants an arm and a leg for them. I kind of wish I had a gasser at this point. I can rebuild a carb for next to nothing and gasoline is cheaper than diesel now. Even if I get my injector problem solved, I've got a cruise control that doesn't work right, a harsh shift from 1st to 2nd and a vibration in my driveline. What else can go wrong? Sounds like I'm a bit of a crybaby but I'm beginning to regret ever buying my diesel. Except for filters, everything is just too expensive for such a cheap car. Now I know why these things are so cheap.

I know its a 20 y.o. car but I've never complained like this about my 50+ y.o. Cadillac. I wouldn't have kept it so long if I did. I was driving that car on a daily basis when I first got it nearly 18 years ago but it never gave me any trouble and it was almost 35 years old then. I drove it daily until I decided that it would not remain in the pristine shape it was in if I kept doing so. So it became a garage queen that I only drive on special occasions.

ohcaptainron · #8 02-28-2004, 10:29 PM

possible injection pump, sorry!

lietuviai · #9 02-28-2004, 10:41 PM

Quote:

Originally posted by ohcaptainron
possible injection pump, sorry!

OH NO, I hope not! Those aren't cheap. I've been quoted upwards of $700+ for the IP

Injectors are expensive enough as well. If that is the case,

I'll drive it for as long as I can and then just part it out. I know I can get more money for it that way than selling it in one piece. It's got a perfect interior, including the dash, excellent sheetmetal, good glass and there'll alway be someone who'll want the engine and tranny. Then I'll have fun squashing the carcass with my neighbor's dozer.

BoostnBenz · #10 02-28-2004, 11:28 PM

Yes it is a turbo but the smoke is even at idle when the turbo is off. The tips of the injectors weren't wet with fuel but had a nice layer of carbon on them along with everything else in there. This has been going on for many tanks, granted almost all of them from the same fuel station but many tanks over a long time and the problem is only getting worse.

The smoke is kind of gray, I've seen the real white smoke a diesel can let out and this isn't it. It doesn't look coal black either but it does sometimes leave a little carbon circle on the ground where I start it.

Gas is cheaper than diesel? Not here! (I hope it stays that way too!) Bad can always get worse, I think I have you beat by a mile but no need for me to

here. I'll PM you my list of problems to make you feel better.

They really are great when running right but sometimes well it was a good thing I don't carry a sledgehammer in the trunk....

If it were just an IP I'd be happy meaning if I could put the money into one thing rather than change everything other than the motor to fix it.

Nobody said you have to buy the IP new, just buy it used and do some thorough testing on it.

Eric Eliel · #11 02-29-2004, 01:12 AM

Just is really simple and sounds a little like the problem I had recently. Have you checked all the vacuum hoses that go to the IP and the ARV and the EGR? Make sure the EGR is plugged but also the hose isn't leaking, same with the ARV next to it. Also check to make sure all the various hoses going to the IP are installed and fit well. I think somewhere along the line, one of my hoses was loose causing some of the issues you describe.

Sure you are getting clean fuel and the filters are plugged?

Worse case I have a guy here in SO CA that can test and rebuild your IP for much less than the "on-line" places. He has the Bosch IP test bench. You can PM me.

1stimer · #12 02-29-2004, 02:29 AM

I don't think he has an arv in a 1983. I think we just got lucky in the california 84's and 85's for that. Could it still be the injectors even though they are clean? I am leaning towards the injectors for my similar problem, but I have resigned to pay an expert to diagnose the problem for me. The car goes in next Friday, and I will share any information I get.

R Leo · #13 02-29-2004, 08:01 AM

FWIW, my two cars (both OM617.952) are as different as night and day. Almost to the point that they feel like they have different gear ratios. Marlene the wonder wagon is a dog off the line, Lilly is quite different.

After chasing down all the ususal things (clean overboost line, etc)
I corrected the chain elongation on Marlene with a 6° offset key and noticed a slight bit of improvement. I do not know what the exact IP timing is. Some day I'll do the drip thing and set it to spec.

Another weird thing is that Lilly was running (quite well, I might add) with something like 11° of elongation when we got her. I replaced the timing chain about 1000 miles ago, fully expecting to have to retime the IP. After installing the chain I could detect not one iota of difference in the way she performs. And, yes, I did check her valve timing events both before and after the new chain was installed.

Given that these engines make very little HP <2000 rpm, I'm beginning to think that it's not so much a difference in timing but maybe a big difference in the torque converters that makes them so disparate.

shane83SD · #14 02-29-2004, 02:20 PM

Hi Jeff,

What will be the symptom if the injector springs are weak and pop pressure is not per spec, or the spray pattern is not good?
Have you pop tested the injectors?

coachgeo · #15 02-29-2004, 02:37 PM

try this test. Temporarily way back in the back by the fuel tank add a Fauce-Purlater 12v fuel pump. (30 buks at Cheapo Auto Parts Inc. ) Use the low psi one. What this will do is eliminate air leaks cause it pressurizes the lines instead of them having vacuum. If I understand how this pump works correctly it will not overpressure your IP or anything else.

If this solves your problem then you know it is an air leak issue.