How to Repair Relay Control Module (RCM) - (Mystery no Start)
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
Haha, exactly
Now mission is finish, I used many solder for renew joins.
I found also second problem with relay air pump, at the moment I only cleaned it but maybe in future I must buy new or change with horn relay?
I little afraid about my XF becouse the same problem with joins I had with electric seats. Maybe Mercedes used low quality solder in all joins in our cars? This will be drama in future...
Now mission is finish, I used many solder for renew joins.
I found also second problem with relay air pump, at the moment I only cleaned it but maybe in future I must buy new or change with horn relay?
I little afraid about my XF becouse the same problem with joins I had with electric seats. Maybe Mercedes used low quality solder in all joins in our cars? This will be drama in future...
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
I had this problem 3 years ago and pulled the RCM and soldered the 3 connector pins and this resolved the engine stopping and not starting until 2 or 3 hours of cool down.
The problem started again last week . I would be sitting at a traffic light and the engine would stall and not restart until a few hours later. I pulled the RCM board and soldered the 3 pins. This didn't fix the problem. I ordered a new RCM board and installed it, but I still have the same problem where I'm sitting at a traffic light and the engine stalls and won't restart until a couple of hours pass.
Anyone have any info that will help me ?
The problem started again last week . I would be sitting at a traffic light and the engine would stall and not restart until a few hours later. I pulled the RCM board and soldered the 3 pins. This didn't fix the problem. I ordered a new RCM board and installed it, but I still have the same problem where I'm sitting at a traffic light and the engine stalls and won't restart until a couple of hours pass.
Anyone have any info that will help me ?
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Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
I had this problem 3 years ago and pulled the RCM and soldered the 3 connector pins and this resolved the engine stopping and not starting until 2 or 3 hours of cool down.
The problem started again last week . I would be sitting at a traffic light and the engine would stall and not restart until a few hours later. I pulled the RCM board and soldered the 3 pins. This didn't fix the problem. I ordered a new RCM board and installed it, but I still have the same problem where I'm sitting at a traffic light and the engine stalls and won't restart until a couple of hours pass.
Anyone have any info that will help me ?
The problem started again last week . I would be sitting at a traffic light and the engine would stall and not restart until a few hours later. I pulled the RCM board and soldered the 3 pins. This didn't fix the problem. I ordered a new RCM board and installed it, but I still have the same problem where I'm sitting at a traffic light and the engine stalls and won't restart until a couple of hours pass.
Anyone have any info that will help me ?
Bosch CPS.JPG
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
Replaced crank and cam position sensors... didn't do Bosch. Pulling those tomorrow and replacing with Bosch... will check the contacts while installing. RCM soldering... done by my guitar guru. He soldered anything that looked bad... I trust his abilities in electronics in general. Still same choke and die symptoms... jerking like it's missing. Seems to be heat related... starts after cool down. Replaced battery and terminals. Symptoms same. If it is not fixed by replacing the sensors with Bosch... I'll be looking at the RCM again. Sounds like this is where I need to be as maybe a guitar man can't fix this one. Dreading the fuel pump... hope you guys can help. Thanks in advance.
Last edited by CapnRon; 06-30-2018 at 12:01 PM.
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Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
When you turn the key to the ON position can you hear the fuel pump run for about 2 seconds?
If not open the RCM and force the contacts closed for the fuel relay. She if she starts and runs then.
If it does, bad fuel pump relay. It can be replaced.
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
Just actually noticed the fan wasn't spinning... tested the fan with 12v direct... it's good. Fuse was good... so cooling fan module must be bad. Are these serviceable... or paperweights once they are done...? I found one on eBay for $56 and went ahead and ordered to get it on the way in case they aren't. I think this is an overheating issue actually. Will be replacing the sensors with Bosch parts tomorrow anyway.
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
Do you have an image showing which relay is which...?
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
You can find me on Face book if you would like a more "instant" discussion on this.
https://www.facebook.com/groups/241776609949593/
Last edited by Mrmiata; 07-21-2018 at 04:53 PM.
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
Thanks Mrmiata. I replaced the CPS with a new Bosch one first. The no-start occurs when its very warm (Here in Owasso OK, so you know how it is today :-). If I wait for it to cool, it will start.
I'm going to pull the RCM now for a look.
I'm going to pull the RCM now for a look.
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
Once the ECM ( PTCM ) establishes that the engine is running, the relay should close and remain so until the ignition is turned off.
The pump runs constantly creating pressure, the filter contains a regulator for 50-60 lbs of pressure to the fuel rail, anything over that is returned to the tank.
The pump runs constantly creating pressure, the filter contains a regulator for 50-60 lbs of pressure to the fuel rail, anything over that is returned to the tank.
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
When the key is turned to the ON position the fuel relay will engage for 2 seconds to pressurize the system.
After the 2 seconds the fuel relay will disengage until the engine is running.
NOTE- While in the ON position the Engine and Traction relays will engage and remain engaged.
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
Thanks all. I believe the relays are working as designed. I checked the fuel pressure and found that after initial build up it immediately falls back to zero when the pump stops.
I suspect the pump, but will change the filter first.
I suspect the pump, but will change the filter first.
Re: How to Repair Relay Control Module (RCM) - (Mystery no Start)
Today I performed this repair, and when reassembled the crossfire went into limp mode. The only code was "Unknown DTC. Unrecognizede PCODE, HEX CODE: 2066-04. Does anyone have any insight into this? I have searched this forum and google with no luck.