having read the numerous similar threads on this forum and as a new member I find myself with a very frustrating problem. For background, I have (actually my wife has) a low mile (14K) 2005 srt6 convertible. It has run like a clock since we got it in 2007. This year, getting it out of winter storage, I had to crank it several times before it would start (cold start) on 3 occasions. Once it started it ran perfectly fine. Finally, on the 4th attempt, it would no longer start (but cranks normally). I changed the CAM and Crankshaft position sensors (Bosch OEM new) and no change...it still just cranks. What's next? Help...I dread getting fleeced at a dealer and would love to find a DIY solution. Fuses look good, other electronics are working. Did I miss a step in the process? Disconnect the battery? Fuel pump (although I doubt it given the sporadic nature of the problem with normal operation once started).. any clues would be greatly appreciated.. thank you.

 

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With the RCM fault, I understood that there would be no cranking, while I have plenty. Am I wrong?

 

Do you have the ability to pull the RCM out of its box, remove the case from it and study the condition of the contacts inside it. Then with it laying on top of the the case,put the plugs back on it and see if the relays are working correctly when you try and start the car?
There are two solenoid in the RCM that can fail, the fuel pump and another.
Can you hear the fuel pump when you just turn the key to the run position?

 

Have you checked for spark

No matter how much you crank. No spark = no go

Check the easiest stuff first

 

You mentioned that the car was sitting. In addition to spark, the next culprit could be the fuel pump. The pump may fail (the fuse is fine so it would appear that the pump is fine too but it could be pooched or plugged with debris). If you have a jack and jack stands. It's easy to get at and they are cheap to replace. Be sure to relieve the pressure on the line before you disconnect it and always remove the Neg cable from the battery before you begin.

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If not, contact a local repair shop that specializes in MB and BMW. Every city has a few. Go to the shop, explain the problem and when it happens. They may be able to point younin thebright direction or correct it for you for an hours labour plus part.

Please keep us updated. I would like to know the cause once you've isolated it.

 

Spark is good. Fuel is next to check into.

 

Is there a tutorial/pictorial for the fuel pump replacement on this forum...sorry if it should be obvious as I am new to the group and unfamiliar with navigation of the site.

 

from the manual :

 

Is the fuel pump not working? You should be hearing it as I stated earlier. If you give no feedback and just ask questions people will quit answering you.

 

Sorry for the lack of feedback....Scheduling with work and other commitments gives me limited time working on the car, so I am trying to prepare and gathering all of the great suggestions before my next opportunity to get into it arrives (the next few days). So, I am very much appreciative in the meanwhile and will provide feedback as soon as I have the opportunity.

 

Turn on the key and measure the fuel pressure, or at least press the little button on the end of the fuel rail and see if there is pressure (But really, you want to know the pressure, book says 45 or more PSI is what the design calls for).

If the pressure is really low, the injectors wont' fire properly. I mean, face it, you need three things to start the car:

• Air. Air is drawn in by the engine turning over, if the timing chain is intact to run the vavles, you almost gotta have air
• Fuel. THe pump has to be providing enough pressure for the injectors to act.
• Spark. The plugs have got to be firing.

The last two items, the plugs and injectors, are driven by the "Powertrain Control Module". If the fuel pressure is up and the cam and crank sensors are telling the PCM what the engine is doing (how fast it's turning over and the exact timing of the cam and crank), then the PCM can fire plugs and injectors.

 

Brief update, I had a few minutes to check for fuel pump whirring when turning power on and attempting to start, and??? No noise!! Ordered a pump as my next step. Hoping this is it.

 

Did you verify power at the output of the Relay COntrol board? That relay and the Secondary Air relay are the most common relay fails in the RCM.

 

It is possibly the relay for the fuel pump in the RCM, I mentioned that in post #4, cost of a relay $10, cost of a fuel pump $200, Priceless.
Check the cheapest items first so when an expensive part needs replacing you still have the money for it. Do not blindly throw new parts at the car.

 

NO!
As mentioned, it's most likely the fuel pump relay (you DID check the fuse?) in the Relay Control Module.
For $30 I can fix it!
Send the pump back.

 

What makes me less suspicious of a relay is the fact that it worked normally sporadically. A relay or fuse would be all or nothing no? By contrast, a failing pump might sputter out as it seems to have

 

Again, NO. A relay with burned/dirty contacts will act just like what your saying. Seems your bent on replacing the fuel pump. All we ask is come back in if it fixes it, or not. Good luck!

.

 

Actually I've replaced quite a few relays where the coils go bad (open) once the relay has been energized for a bit. Now I apply 12 volts to the relays for a minute to ensure the relays work on the bench before I return them to owners.
You can close the relay manually to see if the problem goes away.


On a side note I've yet to see any other relay, other than the Air Pump relay with bad contacts. Have also noticed more frequently that the "on all of the time", Engine, Traction control and Fuel relays are discolored. Guessing that it's from the heat of the coil.

 

OK, a little more of an update...the fuel pump fuse is pristine as are the relays and solder points (no debris, no heat marks, intact solder). Remembering that this is a 14K mile cream puff. The case for the pump itself seems to be getting stronger unless I am missing something.

As far as the relay itself goes...As I look for a replacement on line, all I find is a 250 dollar unit. All of the other relays indicate that they are not compatible with the 05 crossfire srt6.