Would you mind elaborating on your desoldering setup/technique? I will admit that I tackled the issue of relay replacement as simply an issue of pride - to be able to get my original RCM working again on my own with as little additional investment (other than time) as possible. Also, as a matter of pride I will not say exactly how long it took me to remove the @#$%$*& traction control relay. I managed to do it using a 25W soldering iron, some solder, several inches of solder wick, needle-nose pliers, small screwdriver, wire clippers, and a cut-off wheel on my dremel tool. As you might imagine my technique was not very pretty but I was persistent and eventually had the new relay installed and operating though I'm not sure I would attempt another with this setup.

However.... my Crossfire still would not crank. I could trigger the fuel pump relay by connecting a 9v power source to the coil terminals but it didn't close when the RCM was installed in the car. I went back and reflowed solder at many joints on the PCB and tested for continuity from the pins to the relays. Everything seemed fine. Then all of a sudden the fuel pump relay would no longer close at all and the resistance increased 10 fold. Then it hit me. I had never actually closely checked the fuel pump relay contacts. Once I cleaned them, I put the RCM back in the Crossfire and it cranked and started right up... and stalled after just a few seconds. So then I cleaned up the engine control relay, and now it seems to run fine. So in the end it appears to have been a combination of 3 things - failed traction control relay, and fouled contacts on the fuel pump and engine control relays that were contributors. Since I had been able to trigger the relays from the coil terminals and had verified continuity on the PCB, I had incorrectly assumed that they would operate properly with whatever current would be supplied by the car's battery. I'm guessing the no crank was caused by the fuel pump relay, the no start/stall related to the engine control relay, and all the brake/BAS/ESP MILs and transmission issues were the result of the traction control relay.

 

I would recommend a slightly higher wattage soldering iron (higher than 25 watts, lower than 75 watts) with a 'solder-sucker' attachment/external sucker, for relays on small PCB's. After heating to a flow, cycle the solder sucker making sure you align it flat against whatever your trying to de-solder. I find it takes no more than three to remove most of the solder, and with a slight 'wiggling' of the component it comes right out. If there is a large ground or metal frame, it may take a little longer (or a higher wattage iron) to 'liquify' the solder sufficient to remove the majority. Two things make soldering/de-soldering extremely hard. One is too much heat, the other too little heat. I suggest some practice on old electronics BEFORE tackling must-have parts like the RCM. Good 'soldersucking'!




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Rob, here is how I removed the 2 relays (secondary air pump, fuel pump).
I have a 50 watt radio shack $19.99 solder removal iron with suction bulb on it let it warm up good.
From the bottom of the board I heated and sucked the solder out of each connection several times until I could sort of move the pin or wire. Then I removed the small spring and pulled the half of the contact out that moves. Then I used wire cutters and cut the thick relay frame in half at the shortest point. Next I grabbed one side of the relay frame with needle nose pliers and very very carefully wiggled and pulled
gently one side at a time came right out no problem. Solder each connection carefully on the close ones
make sure not to solder across or together any connections that could cause some real problems. Some of board runs are close together.
Took about 20 minutes to remove 2 relays and 10 minutes to install 2 relays.
Hope this helps worked great for me.
Yellowhammer

 

Other way around, I would think.

 

I thought the same at first; thinking that a no start with crank would be the result of the fuel pump relay not enabling the fuel pump to operate thus starving the engine of fuel. However, if the fuel pump relay malfunctions to the point were it won't close at all, the PCM disables the ignition/starter so you get no crank. The engine control relay, when closed, allows the PCM to communicate to the fuel injectors to deliver fuel. If it is not operating properly, the engine can still crank, and sometimes even start but once it malfunctions the fuel injectors won't get the current they need to work.

 

When my fuel pump relay went out the car would start and maybe make about 10 feet if lucky before stalling. The car would then start and run until shut off and it would stall again until started a second time.
Contacts were burnt and pitted a little on the fuel pump relay cleaning only is a temp fix it will get you sooner than later.
Yellowhammer

 

Robert,

Received relays, sent PayPal. Thanks.

 

Got my relays today, PayPal sent. Thank you Rob!!

 

A few bucks cheaper today on RockAuto.com. M-B part = $131.79; Chrysler Part = $128.79.

 

I think you just explained my problem
{ fuel pump relay not closing causes the PCM to disable ignition/ starter causing no crank when key is turned to start.}