No crank but not RCM…
 

Hello all

Have been looking over an acquaintances coupe. The symptoms pointed to a bad RCM and so I plugged my working one in. Only an occasional crank for a second or two. Radiator fan did not kick in.

I suspected that it could be a bad crankshaft position sensor but common sense told me that there would be a crank at least although one of the videos in this forum suggests that is not always the case…

I understand starter motor failures are really rare and I have heard it crank like I said. What should I check next? The control module in the fuse block? Try bypassing it to fire the starter?

Much appreciated all. Would love to stop this car going to scrap…

Re: No crank but not RCM…
 

Crank sensors tell the ECU what position and speed the crankshaft has, this has nothing to do with engaging the starter - anyone who tells you different should not be giving out technical advice on this forum or elsewhere. This is an example of my warning to new members in my signature line's link. We have many here who give their 'tech advice' that is not worth listening to. I"m getting sick of it, and I think we need to limit who can reply to threads in tech support areas of the forum.


ANYWAY, you did not mention manual or auto - no cranks beyond the RCM can't be diagnosed without regard to the transmisison, as the configuration is so different.
In this case, I'd try this: Open the Pulse module and press down on the starter relay. If the starter engages, your soleniod and starter are fine. You are then left with:

Battery - terminal voltage below about 10.7 or so will not engage the starter, but will appear to be a "good battery".
Clutch/Shift/Brake pedal interlock (depending on auto/manual)
ECU failure (never happens)
SKREEM failure (if you get crank on three turns of the key but no crank on the fourth, yank off the battery cable, reattach and get three more)

Or maybe a bad pulse module, but not likely.

Remove the fuse cover using the tabs at the arrows; tabs are on the outside of the box.

https://cimg7.ibsrv.net/gimg/www.cro...d4ff390dce.png


Pry up the fuse carrier at the yellow tabs.
https://cimg2.ibsrv.net/gimg/www.cro...a625870c3e.jpg

Unplug the PUlse module, pop the cover off (its not easy) and plug the module back in.
Turn key to ON.
Press down on the starter relay - if hte starter engages, your solenoid and starter are good. (There are two relays, one for the supercharger water pump, one for starter. If you car is not an SRT, you have no pump but you still have that relay, sitting there doing nothing Try both relays, I think it's the one on the right.) This means your battery can power the starter, but if the engine is turning over noticeably slowly, the terminal voltage may be low enough that the ECU won't engage the starter - so this does not completely prove the battery is OK.)

Re: No crank but not RCM…
 

My '04 seems a bit simpler/different. Open slots appear to have no contacts.

https://cimg5.ibsrv.net/gimg/www.cro...449a3902b1.jpg

Re: No crank but not RCM…
 

Thanks Pizzaguy and padgett. The car is an auto. I will have a bash at this next week and report back…

Re: No crank but not RCM…
 

Hi all

I deduced that this is probably the starter module or the starter itself but in the end my friend sold it to a local garage. Thanks all.