Mercedes-Benz Forum banner

1 - 10 of 10 Posts

·
Registered
mb4/94
Joined
·
6 Posts
Discussion Starter #1
I just got my 406 started for the first time in 15+ years, changed oil and filters but it starts pretty hard and then slowly keeps idling faster and faster til it get pretty high then I get nervous and disconnect the fuel

I’ve checked the linkage, return springs , levers the whole thing, return springs have good tension, it’s pulling the linkage all the way back, there’s no slop in the linkage,

What do you think this could be ?
What turns these things off ?
 

·
Registered
1970ish 411.119 Mystery Mog, 1979 L-1116 Hauler
Joined
·
389 Posts
The hand throttle, pushed toward the engine, should cut the fuel and turn it off.

Set the hand throttle for the proper idle speed.

Let it run man...after 15 years it deserves run. Keep your eye on the fluids.
 

·
Registered
1976 416.141
Joined
·
350 Posts
Hello,
Here's a link to a youtube video, at 50 seconds it shows how to adjust the idle with the hand throttle. Hope this helps....
Rick Montez
416.141

 

·
Registered
mb4/94
Joined
·
6 Posts
Discussion Starter #4
That’s what I meant by I’ve checked all the linkages

The handle for the manual throttle is all the war clockwise, to the engine (right)


I can’t slow the engine down or shut it down without cutting the fuel
 

·
Registered
1976 416.141
Joined
·
350 Posts
Thats interesting........The answer to your question is.... the injection pump (IP) controls the flow of fuel to each cylinder and when you move the hand throttle all the way clockwise (up against the engine cover) you should be moving the lever on the IP to the off position (no fuel flow). See attached picture of one of my old IP's. The lever is all the way to the rear of it's travel at no flow and moves toward the front at full flow. The unit in the picture is no flow at about 1 o'clock and full flow at about 11 o'clock. That lever operates the "rack" inside the IP which turns the barrels which adjust the amount of fuel that is pumped to each cylinder.

I can think of 3 scenarios that might be the cause
1-The IP lever does not move, IE the linkage does not cause movement of the lever
2-The rack inside the IP is frozen
2-The engine is ingesting oil from the rocker arm side of the engine cover although I think this is unlikely

Here is what I would do.......
Confirm that moving the hand throttle corresponds to lever movement on the IP-if no lever movement then that is a problem
Disconnect the rod on the IP lever and manually move the lever through it's travel, you should feel resistance from internal springs from 11 O'clock to the 1 O'clock position- if no resistance than than points to a stuck rack. Follow the link below for a Bosch IP video on IP operation it will give you a good idea of how they operate.
For the oil ingestion I would pull the engine cover and make sure you don't have oil pooled up on top of the valves

There's a lot of smart guys on this list, they may have different ideas.

Good Luck
Rick Montez
416.141

 

Attachments

·
Registered
1970ish 411.119 Mystery Mog, 1979 L-1116 Hauler
Joined
·
389 Posts
My vote is #2. Try to move the lever through the full rack stroke. If no resistance, then it's stuck.

The IP needs oil to operate properly. My old IP on the 411 has a sump and fill tube on it and I put synthetic motor oil in it.

Your IP on the 406 is hooked up to the engine oil circuit. Let it warm up and put some clean oil in it. Perhaps with time it will free up and operate properly.

Have fun!
 

·
Registered
1976 406 w/ backhoe and dozer blade, a small collection of implements too
Joined
·
1,404 Posts
All of the ideas above are excellent ones.

For my dumb simple one I ask: Do you have a remote throttle for operating a backhoe? Perhaps tucked away in some corner of the back of the truck you might not have noticed? They are usually pretty mobile as you'd clamp it on the backhoe when operating it, and coil it up and tuck it away when the backhoe was not mounted.

Those are usually a simple cable affair with the set point held by a friction knob, usually with lever on it for convenience.

The cable pulls on the throttle pedal, and when rusty, they have a tendency to misbehave. Till I gave up an cut the damn thing, I'd have to go out to the back of the truck to shut it down as the cable would some how creep when the engine was running and the hand throttle in the cab would have no effect.
 

·
Registered
1985 416 DOKA mid-mounted Rotzler winch
Joined
·
441 Posts
Also a source of amusement if your buddy has one mounted on his tailgate and you keep sneaking up on him and changing his throttle setting....
 

·
Registered
mb4/94
Joined
·
6 Posts
Discussion Starter #9
Right, I took the cover off the rail at the front of the pump, I was told that I should be able to grab the bolt sticking out and pull the rack back and forth, there should be resistance if al was well but mine is frozen solid

Thought? Any way to free this up without pulling the pump for a rebuild?
 

·
Registered
1976 416.141
Joined
·
350 Posts
I'm not familiar with the front cover you are referring to but did you try to move the IP lever? Both the hand throttle and the throttle petal should move it. What was the result?
Rick Montez
416.141
 
1 - 10 of 10 Posts
Top