I'm helping a friend with an '85 300D turbo. It's a lovely car, clean, everything works, 166k miles, and it runs smooth and clean, but has NO POWER AT ALL. It starts well and has a fine idle, not slow or anything, and the throttle linkage goes all the way. But put it in neutral, floor it, and there is no smoke, it just leisurely revs up, like a gas engine at light throttle. I can hear the turbo spool so that is not the issue. In gear it cannot climb even the slightest hill. What could be the problem? Initially I thought it was slow pump timing but since it starts and runs so nicely and does not smoke I think not. Could it be badly adjusted valves or a clogged fuel or air filter? Those are my next suspects but I'd think it would stall with a clogged fuel filter and smoke black with clogged air.

I know I've noticed throttle butterflies on some older 240D's--do the 300DTs have them too? If so could it be out of calibration and staying closed?

Thanks in advance...

George

You have to start somewhere. Fuel filter would possibly be number one. No butterfly on intake this design just free flowing all the time. Would not expect a lot of smoke as sounds badly underfuelled.

No.

No.

The rack in the pump is sticking or stiff.

There is no boost signal to the fuel enrichment on the pump. (ALDA)

The ALDA is stuck.

The ALDA is ruptured.

Try putting it in D and give it full throttle..Engine warmed up.....tell us what rpm's it got to after about 4 seconds. (Stall Speed.) ( Just interested. )

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I would start with the easy stuff first.

Fuel filter change.
Valves adjusted?

If everything else checks out OK, I would turn the screw on the ALDA. My car had the same symptoms and I ended up turning the ALDA screw almost a full turn CCW. Now it runs like a beast.

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

My bet that it's a CA emissions model and it may have little or no boost, a bad turbo, or a plugged trap oxidizer. Even with with the car running right, these cars feel like they have no power compared to earlier year models.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

Check the ALDA vacuum line that runs from the back of the intake manifold, which is on the passenger side of the engine, between the firewall and the back of the valve cover to a little metal switchon the firewall on the driver side. It is a clear line, or should be clear. Mine was broken and I was experiencing the same symptoms you are. I fixed it and now the car actually goes when you put your foot on it. If it is not clear, that is full of oil and grease. Clean it out. Mine was full of crap. I took the line off the car. Then I took a coat hanger, cut the hook part off and straightened it out. Then filed the ends so they weren't sharp. Then I cut a little patch out of fabric, and pushed 3-4 patches through the line, cleaned it right up. Then reinstalled. It helped tremendously.

Hope this helps.
Andrew

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Thanks for all the help, you guys are great. I'll look at all those things. However, I feel pretty certain it has nothing to do with the turbo. I can hear it spinning up when the revs finally climb up towards 3300 or so, so I know it is not seized. I have a naturally aspirated Rabbit diesel, and no matter if the turbo and ALDA are working like new or completely shot, the engine ought to rev up under zero load pretty quick. There's a blockage of something somewhere, I am almost certain of it. Either that or the pump is shot.

Ahhh...first I have to get it running again, my friend changed the fuel filter and now it won't start. Oh well...

After you change the fuel filter you have to prime it for a while with the primer hand pump. After doing that for a good 15-20 pumps or so, (usually you can "hear" a little click/whistle sound when its primed) then try cranking again.

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You cannot dismiss the alda line etc. so easily. Jettas even have a fuel enrichment vaccum or pressure line from turbo to pump. Happens to be almost trouble free system on vw but not so on mercedes. The primary reason for the slow build in revs and low overall top revolutions is fuel starvation. Even though you hear the turbo spinning it is just increasing the air into the cylinders with no corresponding or minimal increase in fuel if the enrichment system on the pump is not recieving the proper signal.. Do not rule out things like rupturered diaphram or obstructed lines as a few have mentioned they are the really common causes of your concern if the fuel filter does not do it.