603 idle computer
 

So, dropping a 603 in a w123. I know there's an idle computer/relay on the 603 and a fine adjustment circuit to it.

What does it need to run? Is it just a circuit hooked up to power, the IP and maybe the tach or crank sensor?

How can I go about making this operate in the w123?

I can't help you with your question, but would love to see pictures!

You need a lotta stuff. Crank position sensor is just one feed. There's an air mass sensor, a thermoswitch (low temp), an air temp sensor, and a barometric sensor. There's a diagnostic plug. A reference resistor. It interfaces with the EGR system. Power comes from an OVP relay. Harness. In order to use the air mass sensor, you need the turbo airbox which breathes through a port on the side of the fender. And finally, there's a solenoid on the back of the IP that adjusts the rack and a sensor which reports rack position. Suggest you start with the FSM and ask as you go. Here's a block diagram of the 190DT version, which is a bit simpler than the 300D:

I'm pulling the 603 from a 87 wagon. I'm keeping the transmission from the 87 wagon as well.

If I plan on using the air cleaner from the 603 it seems all I need to do is keep some of the original wiring and give it power/ground. Is that correct?

You need the rpm sensor by the fly wheel, temperature sensor (not sure which one but its for hi lo idle) computer and an output to the speed controller on the IP. All other signals to the computer can be ignored.

Some light reading...

Description of operation of the fuel system
http://w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Engine/602_603/07.1-0010.pdf

Wiring diagram for the 124
24 Electrical Troubleshooting

I would carefully extract the entire wiring harness from the engine when you pull it. The engine harness joins to the cockpit harness within the fuse box. You may have to do some gymnastics to mate the correct signals coming from your 123 cockpit so I would plan on getting the cockpit half of that harness too.

There are several engine systems you will need that are different than the 123.
- air conditioning system will need to be integrated into the engine controls. The 617 has a direct belt to the compressor but the 603 has a serpentine belt. The engine RPM sensor and the Klima relay are necessary to protect the engine from a seized compressor. They tie into the tach sensor in the compressor to determine if the compressor is rotating slower than the engine.
- the overboost protection is part of the engine harness. It doesn't rely on the ECU but you will need it to protect the engine. The manifold port plumbs through a switch over valve into the ALDA and the blue flying saucer for transmission control.
- the EGR/ARF are controlled by the ECU. Your choice if you are going to run it or not. If you don't then you will be able to simplify the control system by deleting the vacuum transducers at the right front of the engine compartment and the attendant plumbing.
- turbo waste gate is direct controlled in the 87, unlike the later models that rely on the ECU so that is easy.
- tach is derived from the crank sensor. The 603 sensor is 144 pulses/rev (on the ring gear) and the 123 is 1 pulse/rev (on the balancer). You will probably have to pull the tach mechanism from the 124 cluster and figure out how to install it in the 123 cluster.
- oil pressure is a mechanical gauge in the 617, 603 uses an electrical sensor. You may be able to adapt the bung hole in the 603 filter tower to accept the 617 gauge.
- not sure if the temperature gauges are compatible between the 617 and the 603. The sensors may be different.

I would also locate the diagram for a 123 so you can look at integrating the start, glow, alternator, temperature gauge, etc.

If you run into more specific questions let me know. I deal with control systems at work and I'm used to figuring out how to make things that weren't designed to work together play nice.

Some great information above, this is why I love this forum.

The airbox / air flow meter (no mass air sensor in these old cars) is only necessary if you're going to use the ARV/EGR, many of us pull that out, you might not have the space anyway.

The A/C clutch is a great catch, as it has the speed sensor to turn it off if the compressor is seizing or otherwise has an RPM mismatch (slipping belt etc.). You could probably eliminate this circuit, especially if you're going to adapt your A/C compressor or eliminate it.

The 60x glow plug system is a parallel system. If it's a 3L 603 it doesn't have afterglow so it doesn't need a temperature sensor, if a 3.5L it will need the dual temperature sensor to run your aux. fan and the glowplug relay.

The vacuum system can be simplified, I believe that the BFS has been removed successfully.

Overboost protection is IMO hardly necessary with the stock settings and the stock turbo, if you modify the engine add a boost gauge. Without it you can also remove the SOV and associated plumbing, run the manifold pressure hose directly to the ALDA. The ALDA will help you keep overfueling to a minimum off-boost, IMO it is preferable to keep that.

MXFrank also mentioned the idle control plug, the round plug near the fusebox with numbers around it. This will be required if you want the idle speed control. Idle speed control is a nice refinement to compensate for the automatic transmission in drive and for air conditioning (and to a minor extent the alternator). If you are running a manual transmission and no A/C there will be very little effect and you could consider leaving that whole system out, and running the IP from the mechanical stop only.

The 603 alternator is internally regulated, should be easy there.

Pull the oil cooler of course.

You can go simple, and run all mechanical, or complicated to have all of the refinement of protections and a stable idle, depending on what you need.

I thought of something else. I assume you have confirmed that the inline 6 engine is going to fit in an engine bay designed for an inline 5 (or 4)? Will the engine mounts line up to the existing points on the 123 subframe? And will doing so allow enough room for the radiator up front and allow the transmission to fit properly in the tunnel?

If I am wrong and it's been done before let me know, just didn't want you to get into this and discover it won't fit.

I've heard of many 606 to 603 swaps from 210s into 124s but can't recall one with a 603 from 124 into 123.

Lots of such swaps in Finland. Remember the 123 was also available with 6-cyl gassers as the 250 (M123) and 280/E (M110).

http://www.peachparts.com/shopforum/...bo-dzuorsg.jpg

Sixto
83 300SD

Cool! Just wanted to make sure the O/P wasn't heading for a dead end....

The Klima is an interesting question. Is there a Klima relay in a 123? I don't believe so. If simplifying, it can go, as it's primary function is to keep the belt from shredding if the a/c clutch seizes. In my experience, it mostly malfunctions due to the belt slipping. The Klima relay also powers the kickdown solenoid on 124s'. I think there's a different power source in a 123.

I see no point in eliminating either the Bufo or the overboost switchover, but you certainly could.

The tach won't read correctly, as it's set up for a five cylinder motor. You may be able to transplant the guts from the '87 tach, this would be a project in it's own right.

You will also need the EGR transducer.

(The tach won't read correctly, as it's set up for a five cylinder motor)

i can see that if it was a gasser but it seems that these pick up off the crankshaft.
rev's are the same at either end.

I could be wrong, but I think the sensor feeds the computer, which creates it's own RPM signal for everything downstream.

A 601/2/3 tach shouldn't care how many cylinders are spinning the crank but it won't properly display a 617 signal, nor will a gasser tach properly display a 601/2/3 rpm signal. '85 617 with RIV might be an exception.

Sixto
83 300D

The tachs are not interchangeable

OM617 tach derived from pin on balancer = 1 pulse/rev
M10x tach derived from spark = 3 pulses/rev assuming a 6 cyl
OM60x tach derived from ring gear = 144 pulses/rev