I recently purchased a 1985 300D - turbo and have started working on it to get it set up to drive back and forth to work. My questions are as follows:
a) I am planning on "rolling on" a new timing chain and was wondering if the oil pump chain should be replaced at the same time. Mileage on the car is 215k. Has anyone on here ever seen the oil pump chain break? Can this be done without removing the engine?
b) There is a small solenoid valve (electric/vacuum) mounted on the firewall right behind the brake master cylinder. When I was nosing around under the hood I found the electrical connection unhooked. I hooked it back up but have not driven the car to see if it makes any difference. Can anyone tell me what this is?
thanks,
Jim
'95 E320
'97 CRV
'85 300D

Hi Jim,

I don't think you need to worry about the oil pump chain, but you should be able to replace it through the sub pan.

The solenoid sounds like the overboost protection switchover valve. Its job is to cut the boost signal coming from the intake and going to the injection pump aneroid if the boost hits some value much higher than the waste gate pressure. I have seen many of the sensor switches go bad causing this to energize. A distinct loss of power occurs in such an event. Unless its just an accident I imagine someone disconnected it for such a reason. The chances are much greater that the system will fail than the boost go too high. The test is to tee in a pressure gauge into the line going to the aneroid. You should get about 9-10psi at full boost. If its low (the more common problem due to carboning of various choke points)the car will have no power (this is the number one cause of such things). If it is too high around 18-19 psi then the car will fly until the cutoff takes place and then drop almost like someone shut off the fuel as the power drops and the boost drops the cycle repeats causing a horrible bucking. Power off, power on, power off, power on etc.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

After reading about the "banjo" fitting on the end of the intake manifold I went out to the car to nose around some. I cleaned the banjo fitting and also found that the plastic hose at the banjo fitting end had a hole in it. I cut it back to insure that when I put it back together I have a complete hose here. Also, while I had the hose disconnected at the banjo fitting end I unhooked the hose at the aneroid compensator and blew through the hose at the intake manifold end. I did not get anything out at the aneroid end of the hose (this was all done with the car off). I strongly suspect that the overboost protection switchover valve is plugged up. I will pull it off tomorrow and see if I can get air through it. How much trouble could I get into if I just ran the hose from the banjo fitting straight to the aneroid compensator and bypassed the switchover valve? The car has about 215k miles on it. Also, I will eventually get around to putting a pressure gauge on the line from the banjo fitting to see what kind of boost pressures I am getting.
thanks for replys/comments
Jim
'95 E320
'97 CRV
'85 300D turbo