Ok, I really need some guidance!! - PeachParts Mercedes-Benz Forum

psaboic · #1 02-26-2011, 07:40 PM

Folks, I've got a sick Mercedes on my hands

Car in question is an 84 300D Ran like a top until work was recently done on it. It had all the air and fuel filters changed, an oil and filter change and a valve adjustment and now it runs like pure hell.

SYMPTOMS:

It will start fine and idle well at about 650-700 RPM while cold, but starts to run worse as the motor warms up. If you take it on the road cold, it runs ok until it warms up, then it runs worse. When I mean running worse, I mean once warmed up it will stutter/miss at about 2000 RPM, and bog down if you try to put any load on it. Then in about another minute or so the motor slowly loses RPM no matter how much throttle you give it. Eventually it gets so bad you are going about 10 MPH with it floored, and if you take your foot off the accelerator the motor will die. You can re-start it but it idles bad. It will slowly rev up, but as soon as you engage the transmission, it chugs and tries to die.

If you let it get warm in the driveway it runs smoothly while cold, but as it warms up the idle starts to become VERY rough and will drop to 500 RPM and the whole motor shakes like a paint mixer. You can try to rev it but if it builds RPM it does so slowly and chugs badly. like it is only running on 3 cylinders. If you are able to get it above 3000 RPM , it is rev happy and smooth, then you let off the throttle and it instantly dies.

Let it sit until cold and start it and it is fine until it warms up, then it runs like hell again

In order to trouble shoot it, here is what I have done. Changed the primary fuel filter with a new one again. No change. New air filter, no change. Cleaned the tank screen (not dirty at all) and blew the tank feed and return lines clean. No change. Removed the lines from the IP and the secondary fuel filter housing and blew them clean, no change.

Lastly I tried to isolate the fuel system. I hooked up a 2 gallon fuel can to the primary filter and then used the return line from the secondary fuel filter housing to go back to the 2 gallon can. On the road it ran better but still had the 2000 RPM stutter/miss. Idled better too but still started to run worse as the motor got warm, just not nearly as bad or as fast. Back home I re-hooked up the regular fuel system, and it ran a lot worse and almost died out and stranded me.

So, what the hell could have caused the problem(s)? I'm down to maybe a bad secondary spin on fuel filter (even though it is brand new) or a screwed up valve adjustment. After that, I'm out of ideas.

Based on what I described, what would you do. HELP!!

babyjames · #2 02-26-2011, 07:45 PM

On the fixing bolt for the secondary fuel filter.

Jay.

psaboic · #3 02-26-2011, 07:48 PM

Thanks for the reply, but I am not sure what you mean?? I didn't notice any leaks at the filter. The bolt did have a small O-ring, but it looked ok.

babyjames · #4 02-26-2011, 07:52 PM

Check for air in the "clear" plastic line running from the filter mount to the IP. If bubbles are present, I'd place my money on that o-ring. I replace said o-ring as a matter of course when replacing the spin-on filter.

Jay.

Stevo · #5 02-26-2011, 07:58 PM

Why dont you take it back to the folks that did the work? didn't you notice the problem after driving out the shop door?

leathermang · #6 02-26-2011, 08:02 PM

Those are classic symptoms of valves set wrong... ( too tight, thus elongate when warming up and do not seal at the valve seat..... so much of the cooling of the valve is from convection to the head... that it is like a microphone scream... a vicious cycle.. not pressed against the head... heats up faster, elongates , presses even less, heats up even faster... a feedback cycle... all going the wrong direction...
better check them fast because you can burn them in a heartbeat...

bobodaclown · #7 02-26-2011, 08:11 PM

Quote:

Originally Posted by leathermang

Those are classic symptoms of valves set wrong... ( too tight, thus elongate when warming up and do not seal at the valve seat..... so much of the cooling of the valve is from convection to the head... that it is like a microphone scream... a vicious cycle.. not pressed against the head... heats up faster, elongates , presses even less, heats up even faster... a feedback cycle... all going the wrong direction...
better check them fast because you can burn them in a heartbeat...

X2 check the valves.

barry123400 · #8 02-26-2011, 08:44 PM

If the problem started right after the valves where adjusted I agree with the two prior posters. Clearance of the valves must be checked again.

Post if it is or was not the issue. No sense looking other places if the above was the sequence of events..

psaboic · #9 02-26-2011, 08:51 PM

Quote:

Originally Posted by Stevo

Why dont you take it back to the folks that did the work? didn't you notice the problem after driving out the shop door?

Because a friend and I did the work ourselves. I have done valves on OM617 twice before and never had an issue so I didn't think anything of doing it again

Anyway, looks like I'm going to be doing the valves again but it may be a day or two as it is snowing like crazy and 27 degrees here right now and the garage is not heated. I'll also check the clear line by the IP. Where can I get the o-ring? Anywhere locally, or does it need to be ordered from a vendor.

Why would it run better although still not right with the external gas can?

As for burned valves. Good God I hope not. It has only about 50 miles on it since they were adjusted and about a half hour of idle time. Forgot to mention, no bad smoking or anything while it is running like crap

barry123400 · #10 02-27-2011, 02:02 AM

Since you adjusted two 617 valve clearances before with no issues. They should still be quick checked for clearances making sure you have the clearances for intake and exhaust valves not confused.. With your previous experience they will probably be okay.

Other than that at the moment it depends on how you feel about coincidence. In the general scheme of things you may have a partially obstructed fuel tank filter, A weak lift pump or open relief valve on the injection pump. Any of these things may contribute to the differance on the can feed. As mentioned before have a look at the fuel in the return line at the pump for excess air.

I actually am having a hard time understanding what you may have disturbed to account for this that other threads have not covered. The most abstract thing I thought about was you introducing new fuel at the time of the repair to the car that was bad. Running on the container did not use the same fuel as was in the tank I suspect. If it was get a little fresh fuel somewhere.

I just re read your original post. It also sounds very much like fuel starvation or air if not the valve clearances. You by the way just have to check the valve clearances not do them again unless the need is indicated.

psaboic · #11 02-27-2011, 04:49 PM

Long story short, the 300D is fixed!! Runs like a scalded dog and is a smooth as butta!

I took everyone's advice and re-checked the valves. They were all fine, but just to be sure I set them all a little loose. Re-checked them again and then took her for a test drive. NO change!! Still ran like crap.

Back home I checked the lines coming from the fuel filter housing to the IP. No air bubbles with the engine off, no bubbles with it running. Last resort was to change the secondary spin on fuel filter even though it was just changed less than 100 miles ago.

Took her for a spin, and WOW!! Like a brand new car. Idles great, shifts smooth, and hits 80+ with hardly any effort.

Am I happy it is fixed, yes. Am I pissed about all the trouble a supposedly brand new filter caused. You bet.

Anyway, lesson learned is when you are doing all the filters and a valve adjustment, change one thing at a time and test it before doing the next thing. Saves a lot of trouble.

thanks to all for the help and advice.

Glenn

barry123400 · #12 02-27-2011, 09:54 PM

I would cut the bad new filter apart to see what is accumulated in there. Also may get another new filter free but highly unlikely from where you purchased it.

Good to know some new filters may have an issue as well. Do you mind posting the brand of that filter. They in my humble opinion are a rip off.

psaboic · #13 02-27-2011, 10:02 PM

Actually, I did cut it open about 2 hours ago. Didn't find any sediment but found what appears to be disintegrated parts of the filter material in the bottom, and it looks like the internal parts of the filter came apart and clogged up the flow.

The filter brand was Mann. Never had an issue with them before but the Napa gold filter I replaced it with seems to be working well!!