I certainly hope someone out there can help me with this one. I have an 87 300SDL (OM603) with 250K. Since cool (not really cold) weather started happening, I get no (zero on a gauge) boost pressure for one to three miles driving then suddenly and I mean suddenly within a second or two I get boost and all is well. First thought was a protection valve or some electronic thing, BUT... I have hooked a gauge directly to the manifold, disconnected the line running to the ALDA, and it still does it. All the vacuum stuff, EGR etc on the right side of the engine has been disconnected for over a year since I put on a new head. I jammed the waste gate closed with no effect. Of course with the ALDA disconnected I only get a small amount of power increase when the boost comes on, but I do still get boost. What can make the pressure build so suddenly? There is a vacuum operated valve on the turbo itself that has always been disconnected since I got the car. Could this have something to do with it?

Trace your boost line from intake over to saucer looking thing on left fender well. Temporarily, take it out of the picture and just connect the 2 lines together right there. Run it down road, but not hard because you have no overboost protection, and see how it runs. Mine got gooped up and I had to change it.

My 85 has a ARV valve that keeps the boost from developing until higher rpm. I blocked the vacuum control off. It used to come on the boost very suddenly, like a light switch. Now it builds from much lower rpm.

__________________
85 Merc 300D - Unwinding 31 years of wear
86 VW TD
Mahindra Diesel
Iseki Diesel

In 2007 I didn't own a diesel.

Thanks for the input. The flying saucer is OK . I will look into the ARV. Mine is also blocked off, but it must have something to do with it. I am leaving town and will have to live with the problem until I get back.