Hello, I'm Bruce. I've recently purchased my second diesel MB. My first was a 78 300D that looked pretty good on the surface but had a lot of problems mostly created by the previous owner(s)? Enough said it's in the past.

My new one is a 1984 300SD - The body is perfect the only issue is the chrome plated wheels are flaking. Inside there are a couple of small items that will need some tending. I'm on a list of 20 year old motorcycles and we call these things "farkles".
The first "farkle" is the glove box - will not stay closed.
The second is the air control does not blow air to the floor.
The third is the clock and tachometer do not work.

I was out on the web last night and ran across some owners talking about getting ready for winter by cleaning out the intake, cleaning a banjo bolt, and adjusting the valves. I can do the valves but what about the other two - what do I need to do?

And finally - this car will not start in the cold (30 F) Just a small shot of ether and she takes right off. I'm assuming glow plugs but where do I start.

Thanks,

Bruce

Welcome, Bruce!

Well, you have quite a repair list there, so let's start at the top.

1. Can't really e-diagnose your glove box problem except to say make certain the screws are all tight, and the latch on the door is not broken. IIRC, the latch a made out of plastic and if slammed enough times, just breaks, but is an easy repair (replacement).

2. The vent control operate on a vacuum servo system. If that is the only thing wrong with the a/c, then the servo is likely bad (unless the line to it is disconnected), and needs to be replaced. (I'm not sure where behind the dash that this is, maybe another person on the forum can clue us in)

3. A number of possibilities. First, check the fuses. The proximity of these two "gauges" tells me there could also be a short behind the gauges. Also, the problems could be independent. I THINK the Tach works off of a reference sensor (http://catalog.eautopartscatalog.com/cherokee/wizard.jsp?partner=cherokee&clientid=importpartsonline&baseurl=http://www.importpartsonline.com/&cookieid=1DO05SQJ11DO05SQJ0&year=1984&make=MB&model=300-SD-002&category=F&part=Reference+Sensor) that could be a culprit.
Scott, please correct me if needed.

4. Cleaning out the intake is really more a target of opportunity than a maintenance item. If you have the chance to clean it while it is off for some other service, then by all means give it a good cleaning.

Sludge builds up on the inside from the turbo blowing oil and basic crankcase ventilation. Eventually this restricts airflow. The place where this matters most is at the air line (looks like a vacuum line) that connects the intake manifold to the injection pump (actually the ALDA atop it). The mentioned line (shown here (http://web.infoave.net/~ontheriver/automobiles/300sdalda.htm) ) also gets plugged. The line and its associated fittings (one of which is the banjo bolt, shown in the first picture in the bottom left) can be cleaned with brake cleaner to make certain that air flows freely through it.

5. The glow plugs are tested by disconnecting them from the wiring and measuring their resistance with an ohmeter. If any reads infinite resistance, it needs to be replaced. I the winter, it actually helps to wait for the glow to go out, take the key out, then let it glow again before starting. This lets the plugs get extra hot for that extra push needed in the cold.

HTH.

Sludge builds up on the inside from the turbo blowing oil and basic crankcase ventilation. Eventually this restricts airflow. The place where this matters most is at the air line (looks like a vacuum line) that connects the intake manifold to the injection pump (actually the ALDA atop it). The mentioned line (shown here ) also gets plugged. The line and its associated fittings (one of which is the banjo bolt, shown in the first picture in the bottom left) can be cleaned with brake cleaner to make certain that air flows freely through it.

Good reply Neil. The black sludge which accumulates in the intake manifold is primarily caused by a combination of oil mist being introduced in the air filter housing and the exhaust soot from the EGR. Blocking off the EGR with a solid plate will nearly eliminate this problem. The boost pressure line (often mis-represented as a vacuum line) coming off the back of the intake manifold will eventually clog to the point that the ALDA is not receiving boost signal. No boost signal to the ALDA results in the injection pump failing to enrich the higher compressed air concentration in the cylinder (not taking advantage of the turbo boost with comparable increased fuel delivery).

The clock and tach are likely two different problems. Clock - caapacitors; tach - signal amplifier pins not contacting sockets.
-Scott

Thanks, Scott.

Was I right about the tach Picking up off of the reference sensor?

Well I'm going on a week with my new MB 300 SD. I've cleaned the ALDA banjo bolt "clogged" and changed oil/fuel filters. I fixed my tach by replacing the 10 A fuse located on top of a relay inside the fuse box. Tonight I placed an order with "our" sponsor for a glow relay and five plugs. I checked them for continuity and got all different readings. Time to start new AFAIC.

Bruce:

Did you unplug the glow wires harness from the relay prior to taking your resistance readings across each plug? If no, take your readings again with the connector unplugged.

The clock capacitor job is not that bad for a DIY'er. The replacements are readily available at Radio Shack. I have a couple pictures posted at:

http://web.infoave.net/~ontheriver/automobiles/clockrepair.htm

-Scott

Thanks, Scott.

Was I right about the tach Picking up off of the reference sensor?

The tach has a sensor at the crank pulley. There is an inductive marker on the pulley assembly (where the crank angle graduations are). The sensors sometimes fail but the amplifier pin problem is prevalent. The amp is in the diagnostic socket on the drivers fender well. This problem is unique to the OM617 models which have the sensor on the crank at the pulley end. The sensors on the flywheel end have proven much more reliable.

I have some pictures on this one, but no verbage. See:
http://web.infoave.net/~ontheriver/automobiles/tdcamp.htm

-Scott