intermitent lack of turbo on 85 300D

[bznupe30]

Hi there klatta-klatta fanatics

Just last week my wife's baby was not boosting (turbo) like it should. sometimes it would boost, sometimes not. I parked it for a few days, to think about it. My brother in law said it might be the waste gate on the turbo. I thought fuel injector, so I put in an additive. I checked oil level & found it on the low side of the upper & lower hash marks on the stick. I added a bit to bring it to the just below the high hash mark. I drove the car a day later the problem disappeared. It boosted like the true beast that it is. I'm just, getting my cervical collar off now (snapped neck)! What do you think might have been the problem? Clogged fuel injector? Lack of oil reaching the turbo? or some other devious gremlim who is waiting to strike again?

history: bought car 1 yr ago @ 114.5k, now 118k, changed water pump, all hoses w/hose kit, using the orange anti-freeze

to do: full tranny flush & valve adjustment

thanks a lot - moderate do it yourselfer

[jcyuhn]

Problems like this are frequently caused by a lack of boost pressure reaching the ALDA. The ALDA is a mechanical device atop the injection pump which reads the boost pressure and adjusts the fuel delivery accordingly. More boost, more fuel. If the ALDA never sees boost, it never increases fuel, and the result is ~80HP.

I don't have a picture of the ALDA handy. It's on top of the injection pump. Has a blocked off opening for a screwdriver adjustment. Also has a vacuum (well, boost really) line running out the side. This boost line goes to a switchover valve on the firewall. From there it runs to the rear passenger side of the intake manifold. At the intake manifold it connects via a hollow bolt. This hollow bolt is known to clog with EGR stuff and/or oil crud (technical terms there). When it clogs, no boost.

To troubleshoot, remove the hollow bolt and clean with solvent. Remove the tubing and inspect for cracks/breaks. Be sure to check the rubber connecting pieces as well - these sometimes develop cracks. The threeway valves on the firewall are occasionally known to go bad, so you can bypass it to test. Don't run without the threeway for any length of time - this is your overboost protection.

Most likely this 15 minute job will clear up your problem.

- Jim