OK, I have to ask - what does pinching the fuel return line do?

Maybe he has air in his fuel system - like the episode Carlton had recently.

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1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
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If the IP return check valve you noted in the OP is stuck open, there won't be sufficient fuel pressure to build rpms under load.

This is just a test. Don't leave that line pinched any longer than it takes to confirm.

Sixto
87 300D

I'm not ready to give up on an exhaust restriction. Remove the intake so that you can access the turbo and spin it with your fingers (COLD ENGINE). Report back on whether it rotates freely. Also test it for side to side play........see if the bearing is holding the impeller firmly or not.

Got back to this again today... Good idea Sixto on pinching the return. No luck. I even went one step further and put my fuel gauge on the end of the rubber return line: about 20 PSI... seems fine.

I did the exhaust back pressure test again (should have done that immediately after pulling the exhaust). Now with the down pie off, the back pressure is about the same as with the full exhaust connected; around 15-18 PSI at 3000 to 4000 RPM. With the exhaust off, I can hear the turbo whine. I don't know if this is normal. When I get the kids to bed tonight, I'll pull apart the intake on the turbo per Brian's suggestion. Thanks.

Paul

on a different note....have you heard any difference in the sound of the engine? i had my vacuum pump fail on my 93 2.5turbo a few weeks ago that slightly threw off the cam timing. the car started and would run after the vacuum pump was replaced, but displayed the exact symptoms you are experiencing. it had very low power when cold, had a knocking sound, and took forever to get up to hwy speed...but once there would run 80mph all day. back to the shop to find out the cam timing was off. the cam had a hairline crack requiring replacement, but thankfully/luckily that was the only damage (i.e., no valve damage, etc.).

No change in engine sound that I can detect. I noticed a slight lack of power over the course of 2 weeks, then last week, car is basically undriveable.

Turbo spins freely from the intake when turning clockwise looking from the front of the engine, I guess. I mean I can spin it easily using a small screwdriver on the impeller; however, it will not continue spinning like a fan pulley or AC clutch would after I let go. Is this how it is supposed spin? Spinning counterclockwise is slightly lumpy at one point in the rotation. Definitely no play. Should I pull off the pipe with the foil where the trap used to be? This would certainly eliminate any possibility of an exhaust restriction.

Yes, that's exactly how it should perform. The "slightly lumpy" concerns me a bit but I don't believe it's preventing rotation of the rotor.

My turbo when spun by finger continues to spin for a short while after I take my finger off of it. Spinning it backwards is lumpy also.
You might have a restriction in the exhaust side , in the turbo or the down pipe to the turbo.
It is really quick to pull the pipe, you might have a better idea then.

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1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
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Still have not solved. Last night I pulled the exhaust pipe between the manifold and turbo. Same no power problem, so there is definitely not an exhaust back pressure problem. Also confirmed that the flap in the airflow sensor is not stuck.

I put the exhaust back together and let the car idle for a couple of hours tonight; quite a bit of water came out the tail pipe, about a 10" puddle. Diesels aren't supposed to have water in the exhaust like gassers, right? (I've never noticed water from the tail pipe before) At this point I'm wonder if I just got a really bad tank of fuel containing water.

Paul

its possible.


One way to check might be to remove the filter and pour the contents into very clear container. The water will settle to the bottom.

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I'm out of ideas other than the above.

Rig up a small can of fuel under the hood and run the fuel to the primary. Take the return line and run it into the can.

See what you get.

Plugged fuel tank strainer? Swap the inlet & return hoses where they connect to the hard fuel line. If the car suddenly runs great, it was a fuel restriction at the tank.

Otherwise, I'm thinking bad fuel is a good possibility....

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Dave
Boise, ID
Check out my website photos, documents, and movies!

I pulled the ALDA off last night, and the problem is solved! I've never messed with the ALDA, previously. Maybe I should have looked at this sooner...

I don't want to leave the ALDA off permanently. It is possible to get a new ALDA from Bosch? (I don't see as available in EPC). When the pump is new, is the ALDA calibrated on the pump and then the ALDA sealed, or are they all the same? I'll try to adjust my existing unit, but with the way went from normal to no power in a couple of days, I have to believe that this ALDA unit is toast.

Thanks for all the suggestions.

Paul

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as ever
Paul

1989 560SL
1987 300SDL
1987 300TD
1983 BMW 633CSi
1972 280SE 4.5

Leave it off

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86 300SDL. 250,xxx on #14 Head. One eye always on temp gauge.. Cruising towards 300K

Ever driven a 603 that was messed up? Or even own one? Mine was upon purchase and could barely get out of its own way.



Once throttle linkages were adjusted back to spec on mine, it was still running as an N/A car and quite slow. This at least got my pedal back to normal so the rack would open. It could maintain freeway speeds, but city driving was downright dangerous.

I had a plugged up over-boost solenoid. I simply bypassed it and the power returned big time, then I gutted the cat under it to finish the job. A 300D I fixed with the 603 had a plugged cat under the car and the ALDA needed to be adjusted for throttle feel off boost.

I would highly suspect the cat under the car on all '87 vehicles. I read this a few times and cannot seem to tell if the car was driven with the downpipe removed from the turbocharger or not. Not sure how simply reving with no load is going to be an indicator of restriction.

Also on the fuel issue, just purchase some fresh and stick it in a sealed jug and attach to the fender to take water in the fuel out of the scenario.



EDIT - seems like the ALDA is bad, well forget what I just typed. FWIW, my ALDA has been gone for years with no adverse issues.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

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