Power Loss 83 300D - PeachParts Mercedes-Benz Forum

rmmagow · #1 10-26-2002, 06:03 PM

Today it is really pouring rain. Anyway, my 300D all of a sudden felt like it lost all power, thought I'd have to pull over. I read some posts about the EGR valve maybe being screwed up. How can I test this? Nothing's been done to the car recently and it's not smoking at all except at startup. How can I access the turbo to sort of spin it a little by hand and check for play in the thing. I can't hear so I have no clue if the thing is squealing or anything.
Is there a wastegate on this turbo set-up that might have hung up open? Could heavy rain cause problems? I wouldn't think so with a diesel but.... Same fuel I've been using for months. Car is used mostly at hi-speed 70~85 80 miles a day. A/C is not working so it's not the compressor kicking in. Any advice greatly appreciated.

Wasuchi · #2 10-26-2002, 08:18 PM

Fuel filter? I doubt it if it's a sudden loss of power but it's worth a look.

psfred · #3 10-26-2002, 10:19 PM

Most likely a broken boost signal line to the ALDA or a bad pressure switch or switchover valve. This will vent the boost line to the ALDA and deprive you a fuel, hence horsepower.

Check the line from the rear of the intake manifold to the switchover valve on the firewal and from there to the ALDA (big silver "can" on the injection pump). The bolt on the manifold can be plugged, too.

A sudden loss of power sounds like a boost signal problem rather than a turbo -- turbo usually just fades away. They can do fun things like refuse to spin up cold (the Volvo did that) but usually get noisy for a while and start to use oil.

YOu can check the turbo by removing the air filter housing and hose to the front of the turbo. This will expose the compressor wheel. Gently turn it by hand, ENGINE OFF -- please do not leave the compressor wheel exposed with the engine running, very dangerous. It should spin freely with no binding or grinding, and must have no axial play. Some radial play, just perceptible, is OK.

Note that if it takes any effort to turn it, it won't spin up at all!

Peter

rmmagow · #4 10-26-2002, 10:56 PM

Hi Peter, and Thank you. Couple of dummy questions, axiel play, does that mean back and forth, like side to side or is that up and down. What is the ALDA things purpose in life? Could there be a slight popping sensation/noise when that starts to act up. Although I can't hear, while driving the past two days I thought I felt a kind of high frequency sputter almost like the exhaust had a hole in it (it doesn't, checked that). Only felt it at hi speed and under acceleration. Am I driving this thing too fast? 80 or so when I can get away with it which is most of the time. Does the ALDA function like a waste gate? I'll tear off what I can tomorrow and poke around. I don't know the history of the car and basically it appears to have been taken care of, i.e. no sludge in valve cover, pretty clean air filter and when I changed the oil the first time it didn't seem too thinned out. Pretty hard to gauge when you get a car with 166K on it already. Hope it's not the turbo because it looks like a miserable knuckle breaker to get out :-)

rmmagow · #5 10-27-2002, 09:21 AM

OK. Took off the air cleaner assy and the turbo elbow and checked the turbo play and turn. Smooth, no effort to turn no play up and down or in and out so it's OK. the turbo elbow has a seal at the air cleaner end, 617 098 00 65. It wasn't listed in the FastLane data base but the elbow 617 098 05 01 is listed. Does anyone know if the elbow is both parts? The seal is deformed and I'd like to replace it but will replace the whole thing if necessary. On top of the exhaust m'fold is an electrical switch of some sort. What's that for? Boost pressure switch? Since I'm having some problems should I just replace the thing? The ALDA, I see, from firewall side towards front of engine 1. the oil filter housing, 2. some kind of plastic thing with what I'm guessing are vacuum lines coming off it, some leading to a part that's kind of in back of the brake booster, 3. A squarish metal housing, part of the injector pump ass'y. It has something from the linkage attached and the linkage moves up when actuating the linkage for acceleration. Which, if any, of these are the ALDA? The air cleaner housing and the air filter itself have a little bit of oil on them, not a lot, doesn't drip or anything like that. I am going to clean the housing with a rag and put in a new filter anyway. Is this oil anything to be concerned about? I see no fuel leaks, the clear filter does have an air bubble in it but it's had that since I got the car. I can't find anything wastegate like to check, is there one on this car? Thanks for all your help.

psfred · #6 10-27-2002, 11:33 AM

The electrical switch is on the intake, not the exhaust, I think, and it most likely is the pressure switch.

Turbo is probably OK -- axial play is along axis -- straght in and out, radial play is side to side.

Funny popping noises and intermittant loss of power sounds like leaking fuel lines to me -- if the suction line from the tank is bad, you pull air in instead of fuel. Check the line from the steel pipe to the injection pump for evidence of fuel or deteriorated rubber under the cloth braid. Eventually you will have serious starting trouble if this is the problem.

The ALDA is the aluminum "can" on top of the IP -- sort of squarish. It will have a white plastic line attached, or should have. The shutoff is on the back of the IP, I think, has a brown with blue stripe plastic line on it.

The ALDA (altitude compesator) adjusts the fuel injected for intake manifold pressure. This means it adds fuel as the pressure goes up, so if the pressure sensing line is bad, you don't get extra fuel to go along with the extra boost from the turbo.

If it feels like the car is going comletely dead intermittantly, I would suspect a leaking fuel line -- plugged tank screen or fuel filter usually consistantly reduces power, not intermittantly.

Peter

dc88168 · #7 10-27-2002, 01:35 PM

Hi Peter
I have some questions regarding your earlier post:
You said:
"Most likely a broken boost signal line to the ALDA or a bad pressure switch or switchover valve. This will vent the boost line to the ALDA and deprive you a fuel, hence horsepower.

Check the line from the rear of the intake manifold to the switchover valve on the firewal and from there to the ALDA (big silver "can" on the injection pump). The bolt on the manifold can be plugged, too. "

My questions:
(1) Where is the pressure switch? How do I check to see if it is ok?

(2) If the bolt on the back of manifold is plugged, should I replaced with a new one or it can be cleaned out?

Thank you

David

_______________
1985 300D Turbo

psfred · #8 10-27-2002, 01:41 PM

The banjo bolt (rear of manifold, point to passenger compartment) can be cleaned. Small passage, tends to get clogged with age. Check the line too -- you must be able to blow through it (disconnect it at the switchover valve).

Not sure where the switch is, but it is the only electrical connector on the manifold. On my 300D it is right beside the boost signal line, but that is a 603 engine, not a 617. Probably in the center somewhere if not immediately adjacent to boost signal line.

The switch must be open at normal pressure and closed at about 15 psi. The only way to test is to check for continuity -- if it is closed at atmospheric pressure, replace it. You would have to apply 15 psi or more to see if it closed.

Peter

dc88168 · #9 10-27-2002, 03:48 PM

Thank you Peter

One more question:
"Check the line too -- you must be able to blow through it (disconnect it at the switchover valve). "

Where is this switchover valve? Is this near the Driver side firewall? I saw lots of vacuum lines going thru there. How do I test this switchover valve?

Thank you

David

__________________
1985 300D Turbo

rmmagow · #10 10-27-2002, 04:10 PM

OK. I changed the air cleaner and cleaned up some hoses and tubes. Can't find a banjo bolt in back of the engine. I did remove and clean all electrical connectors that looked like they had anything to do with the fuel delivery or pressure sensing tasks. Fixed a lopsided seal on the turbo elbow, the side leading into the air cleaner housing. Turbo's good, smooth, no play in any direction. The popping sensation I think I was feeling may have been the exhaust system, all the rubber support things but one are broken. I'm guessing it's vibrating against the car under certain circumstances. Took the old thing out for a spin and the power seems to be back to it's neck-snapping, ground-shaking original level :-). I have a feeling this car is going to need and require sort of constant attention unless I decide to restore it completely. I'm much more inclined to sell this one and search around for a cherry 83 ~ 85 w/less than say 100K. This one's allright but I'm really needing a "regular" car that doesn't need so much attention. Thanks you for all your help. I do like working on these cars, I like the diesel. Seems that it will be a lot simpler to fix after I understand it a little better.

Zoonhollis · #11 10-27-2002, 10:14 PM

Maybe some pics will help...

Zoonhollis · #12 10-27-2002, 10:16 PM

...and the altitude compensator...

Zoonhollis · #13 10-27-2002, 10:17 PM

...the switchover valve...

Zoonhollis · #14 10-27-2002, 10:19 PM

...and finally, the wastegate assembly.

rmmagow · #15 10-28-2002, 11:30 AM

WOW! Thanks Matt. Certainly does clear things up when you have pictures!. Side question, what are you using for a camera, it takes nice shots in what is a difficult setting. I am restoring a car next year and want to document the disassembly.
Thanks Matt, and thank you Peter. I believe I have all running right again. Have to fix the broken exhaust hangers before driving it around again.