EGR gizmos - Do I need them?

[Graham]

In searching for rust, I found these EGR devices in the passenger foot well. (1985 300D). My question is - Can I remove these devices or are they linked into some other functions?


So far as I know, when my engine was swapped, it was for an 82 or thereabouts engine from an SD. I don't think there is EGR any longer. Here are some pics of the engine.

[mach4]

Originally Posted by Graham

In searching for rust, I found these EGR devices in the passenger foot well. (1985 300D). My question is - Can I remove these devices or are they linked into some other functions?

So far as I know, when my engine was swapped, it was for an 82 or thereabouts engine from an SD. I don't think there is EGR any longer. Here are some pics of the engine.

The tach is driven off the EGR controller, so you would probably want to keep that in order to maintain your tachometer.

[snookwhaler]

Yea... No EGR or ARV on that one. You can remove the vacuum related crap on the fender well if you follow the vacuum diagrams and cap everything properly. The info. for doing that is on the site. Not difficult to do.

[Graham]

Originally Posted by mach4

The tach is driven off the EGR controller, so you would probably want to keep that in order to maintain your tachometer.

Mach,
I have to remove it to get at some rust up above the controller. But I suppose no harm in leaving it there.

But for life of me, I can't understand how the tach would be controlled by an EGR controller on an EGRless engine

And snook,
I imagine the guy that installed the engine back in 2001 must have capped off all unneeded vac lines because car and other vac stuff works fine.

Thanks for the input guys

[compu_85]

The EGR computer needed an RPM signal to properly meter the EGR. They intagrated the function the tach amp used to do into the EGR computer.

-J

[mach4]

Originally Posted by Graham

Mach4,
But for life of me, I can't understand how the tach would be controlled by an EGR controller on an EGRless engine

While there are no EGR components on the engine to control, the controller (and I would guess, the wiring and engine bay components) were left intact. Here's the diagram of the vacuum system showing the EGR stuff (the controller is circled)


Here's the wiring diagram


And the detail showing how pin 25 goes to the tach



My guess is that when they swapped the engine they left the transmission alone, so you've still got the tach pickup off the flywheel. If they swapped in the earlier transmission then the pickup would be off the harmonic balancer and there will be a tach amp on the fender well. They would also have had to swap in either a tach element or an entire cluster as the tach gauge itself is different.

I spent a lot of time sorting this stuff out when I did the 617 engine swap in the 107.

[charmalu]

Some one could have swapped in manifolds from a 78 or 79 W116 300SD. those 2 yrs didn`t have the EGR. 1980 W116 300SD was the first yr for the EGR.

If you look down behind the oil filter housing, the Tach pick up is on the adaptor plate between the engine and trans. there is a flat spot where the sensor is bolted to the plate.

Charlie

[mach4]

Originally Posted by charmalu

If you look down behind the oil filter housing, the Tach pick up is on the adaptor plate between the engine and trans. there is a flat spot where the sensor is bolted to the plate.

Looks like this

[charmalu]

Yep, thats it.

On a side note, if a manual trans is swapped in, the tach pick up will work on the manual FW.

Charlie

[Graham]

Thanks guys - Great information! That helps a lot!

Mach4 is right - the transmission was not changed, so I guess I should replace that controller after I clean up the rust behind it!

I have owned this car since 1990 and engine was swapped in 2001 after turbo disintegrated. I found a very good guy to do the swap and never paid too much attention to exactly what he did. I should get the engine number off the block sometime, so I know just what it is I have!

Currently about to spend about $2k on non-cosmetic rust repairs I am trying to do the smaller stuff myself, so that's how I got to look up behind that controller!

[compu_85]

What does the trimming plug adjust?

[Graham]

Originally Posted by compu_85

What does the trimming plug adjust?

I read somewhere that it was idle speed, but can't find the link. Perhaps only on 85 W123 and W124's? Perhaps it is used to calibrate the tach? Couldn't find anything in 123 manual.

[compu_85]

Ya, on 86 and 87 cars it adjusts the idle speed, but the EGR computer doesn't control idle on the 85s.

-J

[mach4]

Originally Posted by Graham

I read somewhere that it was idle speed, but can't find the link. Perhaps only on 85 W123 and W124's? Perhaps it is used to calibrate the tach? Couldn't find anything in 123 manual.

I read idle speed as well, however there is nothing that connects to the IP that would do the job. You've got 3 sensors - rack position, coolant temp, and RPM; and controllers - switchover valve and vacuum converter. Since the only thing you could trim would be the two controllers, that's obviously what's going on. And since you have nothing to control (its been removed) you can ignore the trimming plug.

[charmalu]

The 84 300D and SD have this same set up.

Charlie