Mercedes Part Number 001 510 70 97

[Adriel]

Is this the fuel enrichment relay? When I was younger wasn't understanding what I was doing, so now that I have to button up the anti-sway bar task, figure best to understand what does what.

How does the fuel enrichment work?

E.G.R. and the wheel well relays eliminated as leaked badly and N.L.A. to my knowledge. But, hopefully didn't do something wrong...

[sixto]

Fuel enrichment relay in an '85 TD? IIRC fuel enrichment is mechanical with a vacuum switchover valve in the circuit to cut the boost signal to the fuel [de]enrichment device.

As to how it works, there's a device atop the IP called the ALDA. Absent a boost signal from the intake manifold, the ALDA presses down on a plunger in the IP to restrict fuel to about as much as a naturally aspirated engine can handle. As manifold boost builds, a boost signal is piped to the ALDA which responds by releasing pressure on the IP plunger, allowing more fuel in relation to a denser air charge into the cylinders. The overboost circuit has a 1.0-1.1 bar switch in manifold. At the setpoint, presumably because the turbo has lost its ability to limit to boost to levels safe for the engine, the switch completes a solenoid circuit within the switchover valve to cut the boost signal to the ALDA. The engine is essentially limited to it's naturally aspirated equivalent's fuel supply until manifold pressure drops below the overboost setpoint.

Sixto
87 300D

[Adriel]

Originally Posted by sixto

Fuel enrichment relay in an '85 TD? IIRC fuel enrichment is mechanical with a vacuum switchover valve in the circuit to cut the boost signal to the fuel [de]enrichment device.

As to how it works, there's a device atop the IP called the ALDA. Absent a boost signal from the intake manifold, the ALDA presses down on a plunger in the IP to restrict fuel to about as much as a naturally aspirated engine can handle. As manifold boost builds, a boost signal is piped to the ALDA which responds by releasing pressure on the IP plunger, allowing more fuel in relation to a denser air charge into the cylinders. The overboost circuit has a 1.0-1.1 bar switch in manifold. At the setpoint, presumably because the turbo has lost its ability to limit to boost to levels safe for the engine, the switch completes a solenoid circuit within the switchover valve to cut the boost signal to the ALDA. The engine is essentially limited to it's naturally aspirated equivalent's fuel supply until manifold pressure drops below the overboost setpoint.

Sixto
87 300D

Sixto, THANK YOU SO VERY MUCH!

I do not have an A.L.D.A. as was broke when I bought the Mercedes (would not hold vacuum and the screws are corroded into the hosing). Figured I didn't need it, but the more that I know, the more I disagree with those that say fine to run without. Trouble is finding one that holds vacuum or can be repaired.

Very few on here can or able to answer questions, so had to make my own path. I might be further along if I had more help, but at the same time feel retaining more by making the mistakes. Thus why I did some things wrong that need correcting.

So, what is this part mounted to the firewall? Looks hooked into the transmission system.

I found the one I was looking for by looking up the A.L.D.A., so will get that addressed.

[sixto]

Do you mean the ALDA is off the IP or the ALDA is on the IP but not functioning?

ALDAs aren't subject to vacuum but to pressure. You might in fact damage an ALDA by applying a vacuum to determine if it's intact. Instead, apply pressure and look for nothing more than a slow leak. Any ALDA from '78 through '95 should work on your car so there's a wide range of seconds for you.

I'm not familiar with the '85 TD but I don't think the firewall switchover valve has anything to do with the transmission. Could it be you see a line from the switchover valve splitting with one branch going to the ALDA and the other to the transmission vacuum amplifier? From '86 there's a temperature switch and switchover valve attached to the transmission vacuum amplifier. Maybe '85s have it as well.

Sixto
87 300D

[Adriel]

Originally Posted by sixto

Do you mean the ALDA is off the IP or the ALDA is on the IP but not functioning?

ALDAs aren't subject to vacuum but to pressure. You might in fact damage an ALDA by applying a vacuum to determine if it's intact. Instead, apply pressure and look for nothing more than a slow leak. Any ALDA from '78 through '95 should work on your car so there's a wide range of seconds for you.

I'm not familiar with the '85 TD but I don't think the firewall switchover valve has anything to do with the transmission. Could it be you see a line from the switchover valve splitting with one branch going to the ALDA and the other to the transmission vacuum amplifier? From '86 there's a temperature switch and switchover valve attached to the transmission vacuum amplifier. Maybe '85s have it as well.

Sixto
87 300D

Sixto, thank you so very much!

Well, I remember I did get help on testing and failed; bet it was pressure. My tester is my mouth and have used it many times working on the Volkswagen (vacuum based F.I.). Don't think I could suck hard enough to do damage?

Who can help?

The first two show a black with red and black with green that tee in after the first vacuum buffer; the green thing that I forgot the proper name for...

The third is the fuel enrichment.

[sixto]

This might help - Vacuum Devices, '85 300D-T

Mind the vintage. A lot of links don't work anymore.

Sixto
87 300D

[Zacharias]

Originally Posted by Adriel

Is this the fuel enrichment relay?

Where did that come from on the car? I also have an '85 and have never seen that, to my knowledge.

[Adriel]

Originally Posted by Zacharias

Where did that come from on the car? I also have an '85 and have never seen that, to my knowledge.

Zacharias, number 7. http://www.dieselbenz.info/images/vacuum_engine_pp.jpg

One hose goes to the head and another to the A.L.D.A..

My prior post disappeared so...

Sixto, thank you so very much for the thread, but you are right, all its links are dead... Will read Mr. Carlton's post on the transducer, as this mystery part is teed into the line going to it.

[Adriel]

Looks as if this is number 125 and is a change over valve teeing into the vacuum transducer and A.L.D.A.. Guess another reason to find a working A.L.D.A. ...

[my123ca]

Is it #125 or 126? Its just a regular switchover valve. It is controlled by your over boost switch.

[Adriel]

Originally Posted by my123ca

Is it #125 or 126? Its just a regular switchover valve. It is controlled by your over boost switch.

Thank you so very much for the reply!

125, as 126 looks to be fuel enrichment spoken of earlier.

Hey, notice you have an 1985 California OM617a. Any chance this weekend you can get a couple pictures of where the vacuum lines go? I see the red strip and the green strip, both black, tee in by the green vacuum device (name still escapes me...), but like to know how the third is hooked up and leads to please.

[my123ca]

Heres a clearer illustration. The lines are color coded.

[Adriel]

Originally Posted by my123ca

Heres a clearer illustration. The lines are color coded.

Wow, thank you so very much!
Clearer, so now can see it was 124! Now I can see I was right that goes into the vacuum transducer. However, still not understanding its function...