Saab/1998 SAAB 900 se turbo intermittent no start
I have a 1998 SAAB 900 se turbo, when the cold weather came (Vermont) the car started not starting on the battery alone (had to jump start it) then one day it just would not start. When I bought the car (June 2015) I put in a fuel pump and since the problem started have tried multiple crankshaft position sensors and direct ignition cartridges also tried three ecu modules. Here is what happens. after working on the car with a friend replacing CPS DIC and ECU with no results we put everything back to start except CPS as we can visually see old one is bad, (bare wires) so we put back original DIC and ECU then car starts and runs fine. we take a long drive to warm up engine and then turn off and restart. Next morning the car will not start. We have done this 3 times now with same steps and same results. I know the starter works car turn over I know the fuel pump works by running a jumper from fuse to battery, I know the DIC is good from the times it runs same with CPS I have even put in a new battery with almost twice the cca of original. I have also added additional ground straps from engine to firewall. Any help would be appreciated.
As noted in my profile, my hands-on experience is limited to the pre-1992 900s and earlier. However, I have seen issues similar to yours so the following general information may help.
Sometimes,the fuel pump will not start either due to the temperature, wiring voltage drop (terminal corrosion), or weak battery during the START cycle, but goes fine when tested by jumpering as you did. The battery voltage drop during the start period drops a bit, which is sometimes enough, when coupled with all the other possibilities as noted above, to not start the fuel pump.
So what I recommend is prior to energizing the start cycle with the key, is to jumper the fuel pump and let it run continuously and then try starting in the usual way.
To go beyond this, you would need to measure the various voltages as coming from the cps and ignition module..an oscilloscope or analog VOM would be best. I have the pinout and signal designation map, should you need it.
Hope this helps,