01 June 2026:
Realize it has been a minute since there was an update. Lot of changes in the garage where the M156 Crossfire is being parked. First off, the "CF55" (M113K Crossfire) sold a little while back, and that allowed us to move our 1991 Ford Mustang LX 5.0 out from against the wall where it has been stored under a car cover for 23 years, and prepare it to be back on the road. Nothing at all wrong with the Mustang, other than it has just sat for over two decades, but as it has been inside, under a car cover, it is in great condition. That space it is in will not go to waste, as we moved in a Bridgeport EZ-Trak Series 1 mill, and a Monarch 10EE lathe in that space. Neither is up and running, but will be in the coming weeks. Also in the next month, the Mustang will be going through a refit of sorts, having all of its suspension and brakes replaced, and then a general tune up. Suspension pieces are 35 years old, and rubber hoses and such all need replacing. I won't take up a lot more room here about that project, as these are words for a different forum
The M156 Crossfire will essentially be a Mercedes CLK63 in Crossfire clothing. As such, I have begun calling it the CF63, to differentiate it from all the other Crossfires around here (there are 6 of them here at this moment, not all ours). So, from here out, if CF63 is mentioned, you'll know why. The "old" car is called CF55 for similar reasons.
OK, now with that out of the way, I can mention progress on the CF63. Wiring is still the name of the game. While the car will most closely resemble a CLK63, there are some chief differences. First, the CF63 is a 2 door/2 seat coupe vs a 2 door/4 seat cabriolet. There are two power windows, not 4. The CF63 will use an aftermarket Android radio, not the full COMAND system with two different remote CD changers, and a host of other equipment requiring the fiber optic MOST network. The trunk is a liftgate hatch, unpowered with a mechanical latch. The CF63 is currently planned to retain the pneumatic central locking pump (called PSE in Mercedes parlance) vs the electric solenoid locks of the CLK. The CF63 will have the electronic HVAC system of the CLK. There are other differences. The CF63 will not feature a standard floor shifter, as all Crossfires and CLKs have, but rather will use a column mounted shifter from a W164 (ML-class). The seat controllers are also ML-class. Headlamps will be Crossfire halogen, but controlled by the Front Sensor Acquisition Module (SAM) from the CLK. Same with the tail lamps. So, why do this? In short, the desire for the CF63 is to be able to leverage as many modern conveniences as possible, while retaining the classic look and feel of the Crossfire. There are other ways to do this, as evidenced by the CF55, but I wanted to take this car much farther. And it will get there.
Wiring. There's a lot of it. About 85% of the original wiring in the car has been either clipped out, or abandoned in place. Why abandon it? Usually it is because there are a few wires that are part of a bundle that are no longer used, but too much trouble to unwrap an entire sub-harness to remove them. Easier to clip them off at both ends, and bypass them with the modern setup. For instance, the Front SAM will control the headlamps. Wiring for them in the Crossfire runs from the headlamp switch down under the carpet, to the left side fusebox, and then out to the rest of the car. In the SAM architecture, those wires run from the SAM (which will live in the front left engine bay fusebox) to the headlamps. The headlamp switch communicates with the Front SAM, which then runs the lamps. One upside to this is that the number of high amperage circuits inside the car are reduced, which in turn reduces the threat of a dash fire, as we have seen from some Crossfires as of late. Importantly, the Front SAM takes care of how the lamps are run, and when, which helps prevent dead batteries from lamps being left on, or other features such as automatically turning the headlamps on when it gets dark, or the wipers are on. All those little things modern cars do that we like. Sure, turning the head lights on is not a big deal, but again, looking for the total package of making the car modern. Eventually this car will have automatic speed control wipers (which if you have driven a newer Mercedes, you can appreciate), Distronic (adaptive cruise control), and more. This more or less necessitates the modern electronic architecture that can be added this way.
To that end, wiring at the rear corners of the engine bay are getting complete makeovers. Wherever original wiring can be used, it has been, and then a new "overlay" wiring harness has been created, running across the engine bay, parallel to the original one. All new wiring is being wrapped in proper cloth tape, and closely resembles OEM wiring, so it stays hidden. A few wiring changes were needed to the ESP module wiring, mainly adding a few wires for features needed by the CLK63 architecture, but amazingly the ESP needed very little in the way of wiring to be compatible with the CLK version ESP that will be swapped in. Fortunately, the ESP itself is a 1:1 replacement, and will be easy. As the car will have the 6 piston CLK55 front brakes and 4 piston rears, it was decided to have an ESP with matching programming to go along with them. That will likely get swapped a little later down the line.
In the shorter run, the right side engine bay box, which contains the RCM, BCM and ME2.8 ECU needed to be overhauled. None of that equipment would be reused, so all of it was removed, and unnecessary wiring along with it. In place will be the newer ME9.7 ECU, a FPCU (fuel pump controller) and a relay to run the coolant pump for the water/oil cooler. M156 engines need a lot of oil cooling. All of the M156 cars run a large oil cooler that is roughly the size of the SRT6 heat exchanger. Most of them also have a small radiator oil cooler with a 9" fan in the right side fender well. There simply isn't room for it in this car, so instead will run a water to oil cooler from an ML63. This looks like the oil cooler you see on an SRT6, but it isn't mounted to the engine. It also uses the same water pump that the SRT6 uses to push water through the cooler when needed. The ME9.7 controls the pump via the relay. The FPCU is a new one for us. Rather than run the fuel pump full tilt with a relay, and then have a mechanical regulator (as the Crossfire does at the fuel filter), the FPCU varies the speed of the fuel pump, and under low loads, slows it down, and at high loads, speeds it up. This concept was first applied to the SL55, and then spread through all of the M156 cars that came later. Indeed, most all new cars on the road employ this strategy. See? We're going modern here!
If you have read through that wall of text, don't worry, some pics are coming!
First, we still have messes, but they are getting more manageable by the day. Compared to the last post, this is getting a little neater. Still unwrapped wires all around, but the layouts are coming together. Here we see the ECU box starting to take shape. The F2 connector (body side connector) for the ECU is 100% complete, and you see it connected to the ME9.7 ECU, which fits like a glove in the box. Above it you see the FPCU, and the coolant pump relay. The wires you see are left there to interface to the engine wiring harness, which we'll get to when the engine is installed.
Next, we move to the old fusebox. The Front SAM is sort of jammed in there at the moment. We have a plan on how to neaten that up, but will require a little bit of CAD and some 3D printing. When done, we'll have an OEM look.
Moving to the doors, believe it or not, we need computers there, too. Each door will receive a door control module (DCM). The DCM controls a number of things, including window and mirror. In the CLK, it also controlled the seats (buttons were on the door panels), door locks, and more. We are only using the mirror and window functions at the moment. In the more modern setup, the window motors have sensors that know the position of the window. This allows auto down and auto up of the window. It is also a safety, in that if something gets caught in the window as it is going up, it will stop and go back down. Hopefully not an issue here, but good to know it is there. The motor swap was dead simple. Pull the motor out of the CLK window regulator and screw it into the Crossfire assembly. Piece of cake! The door module in the CLK is mounted to the interior of the door shell, in a purpose made recess. It is both a solid place to mount, and keep it dry. This recess is non-existent in the Crossfire, so improvisation was the name of the game. Holes were drilled in the mountings of the DCM and the door, and it is essentially resting on the bottom of the cutout, and secured with zip ties. In an effort to keep it dry it was placed as inboard as possible, but also plastic was cut as an umbrella of sorts over the module to help shield it. Have done similar in other cars with good results. This rather unimpressive picture hides the true genius of the installation!
Plastic flap down (there is plastic over the top and rear that does not move, too)
Lifting the flap to see the wiring
This past week, power was put to the car for the first time. This picture confirms operation of the Front and Rear SAMs and the headlamp switch:
It's not much, but you get to see that the car lights up without catching fire, which is always an amazing thing when you take on projects like this!
Next up we turned the key to see what else might work, and I was greeted to warnings on the instrument cluster, but still success!
Lots more to sort through, but at least we see of signs of life. Even the gas gauge is working!
Not shown is the HVAC (AAC) system also lit up, and the fan started running immediately, which is excellent. More pics and details to come. This rather small looking progress is actually a huge accomplishment, and moves this project down the field immensely. Coming up will be the wrap up of the wiring, including making it look tidy everywhere. After that, will move into modifying the front core support to move the radiator forward, just like was done on the CF55. Adding the oil coolers after that, and moving ever closer towards engine installation. There are a few surprises that have not been announced in store, so stay tuned!