I'm wondering what it is that's causing my RPM needle to bounce around. It doesn't seem to rise above the actual rpms but it bounces up and down from zero and often doesn't even show any activity. Would an electrical relay be responsible for this? or could it simply be a loose something?

overload protection relay

__________________
1987 300sdl
Engine 603.961

Your 85 TD get the tach pick up off the adaptor plate between the engine and transmission. look down behind the oil filter housing and you will see it held in with a small hex bolt. it has a large black cable going to it.



In the center of the firewall is a plug where the cable plugs into. this cable finally connects to the black box behind the passenger kick panel. this is the EGR control thingy.

The Rack Position Sensor the box at the back side of the IP also has a cable that feed into the box. but this is unrelated to the Tach I believe.

check the connection at the adaptor plate, it may be cracked, and the large plug that connects into the black box behind the kick panel.

there was a thread a couple yrs back, where there was a water leak and corroded this connection.

Make sure the plug on the back of the tach is secure, and the 3 gauges where they over lap are tight for a good ground. some make a seperate ground wire from one of the screws.

Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works