Was away for one week. Went to start no crank. Left on charger over night fired right up. After 2 stops, no crank again, no fuel pump running I either. Just put a new battery in to no love.

 

Went and got my scanner and plugged it in. Turned the key to run. Heard the fuel pump kick on. Fired right up. What is happening? I’m going to put the old battery back in tomorrow as I don’t think that’s the actual problem. And $250.

 

Just leave your scanner on the shelf, this failure does not generate codes cause the ECU is not powering up - THAT is your problem.

Same thing happened to me today - after 12 years on this forum, I finally had "the Mystery No STart".
Mine sat for six weeks, thought I'd drive it today. Got in, turned key, got dash full of lights, but no starter engagement - after 30 seconds at "ON", engine fan warped up to high speed - the famous "mystery no start" that has not been a mystery since about 2009.

Found that the coil of the Engine Control Relay on the RCM was open. Jumpered the relay and car started. I'm sending the bad RCM to DJ for rebuild, and I ordered a new RCM (gotta have a spare) from Autohaus for $135.

Next time it refuses to engage the starter, leave key at "ON" for 30 seconds. If you hear the engine fan warp up to high speed, it's your RCMj, we've known about this since 2009. The failure can be intermittent (as in you case) or a total death as in my case. (The jumper got my car running, but that leaves the ECU powered up with the key off, not a long term fix! )

DJ is in Arizona, he can have yours fixed and back to you before a new one gets to you. But if you want a new one, here ya go:
Meyle 2105400072, 0148300019 Relay Control Module; ASR Control Module SKU: 1356476-2105400072 - Mercedes | 83533078078 898.76 W01331717781 (autohausaz.com)

 

I don't think you purchased the correct RCM. You bought the one for a 1998 to 2000 SLK230. The correct part number for a Crossfire/SLK320 is 1705450305 but a 1705450205 (2001 to 2004 SLK230) will work if you change one of the fuses from 15 to 20 (I think F3?).

 

We will know Saturday, but I'm thinking they are the same and the fuse ratings are the only thing that changes. We already know the difference between the 0305 and 0205 is just the fuse ratings.

 

Oh, and DJ can be contacted at:

tighed1@hotmail.com

 

This is the one I have - https://www.autohausaz.com/pn/MB-1705450305

 

Thanks guys, I will be resodering the RCM and returning a $250 battery tomorrow 😜

 

It can also be bad relays in the RCM.

 

Noted, only 110k miles. Are they common relays that could be had at like digikey?

 

They are not expensive relays but with shipping etc it will be worth it to use the guy that will rebuild it for 52 and lives in Arizona also.

 

Pulling the RCM today. Someone has definitely been in here before. Shitty soldering job, definitely some cold points and way too much. Removed the soldier, fluxed the pins, and reflowed. Relays looked good. Old battery date was Oct 18, so I’ll keep the new one and call it prevented maintenance.
thanks guys.

ps. It was nice to still have the old battery, as the one in my suburban was stone cold dead, my “smart” charger would not kick on. Added jumper cables from the old battery got the charger to run.

 

What happened to my RCM is the coil in the Engine Control Relay went open - we've seen more and more of that in the last few years.
You can prove this is the cause if you connect the cables to the RCM without it being in the case. The fuel, engine control and ABS relays will close when the key is turned to "ON" and in a few seconds, if the engine is not started, the fuel pump relay will drop out but the other two stay closed. If you don't have two relays staying closed, there is your problem.

 

Tanks as always, also ordered a new battery ground cable from FCP. As it was looking a little on the green side. I’ll most likely add an additional engine ground when I receive this.

 

You might read this thread:

My fix for a ground cable to the engine - CrossfireForum - The Chrysler Crossfire and SRT6 Resource

 

Thanks for that. I made it a habit in my early water cooler VWs. Bit me in the *** when I didn’t do my suburban. I will always recommend this for any used car. Or new.

 

With all these crappy computers, one thing that could help with these vehicles after a number of years, is to add a ground or two for the engine/transmission. In the past, this has helped with these crossfires, and I am sure they are a huge help in other vehicles as well (plus it couldn't hurt, for sure). One sign is exactly what you found, the green oxidation at the cable end. Just about any good quality cable will work, making sure the ends are (easily) protected against moisture wicking up the wire.


.

 

Thanks to AutohausAZ and their fast shipping, we know two days early. Just as I thought, all these RCMs are the same. The only difference between the "right" one and the one I ordered, was all the smaller fuses are 15 amps where in the Crosssfire, two of them are 20 amp.

I ordered the one for the SLK230 (cause I didn't really LOOK and liked the lower price )

Anyway, put it in, car started, no naughty lights.

 

The Crossfire and SLK320 only have one fuse that is 20 amp, not two and that is position F3.

 

Yea, DJ corrected me, someone put two 20's in mine, I dont think I did that - likely it was one of the previous owners.
I'd edit all my posts but I'm too lazy.