1996 Saab 900s NA 2.3 No spark, tried everything...HELP

[Pinnacleranch]

It shows 10volts at the #`17 fuse. Cannot find any connectors loose or oxidized. This car was very oily around the engine from a weeping valve cover gasket but we have checked all visible connections. I put a battery charger on it to pump up the battery to full charge. It would crank it over though before.

[Pinnacleranch]

What are the typical things that will disrupt spark if a fault is dectected?

[Digger]

Without busting one open you can't see sticky relays or dirty relay contacts, so turn the key to on and gently tap every relay you can fined with the handle end of a medium sized screw driver. Then check your key on voltage at the coil and see if it changes, if you have something that will hold your voltage probe in place watch your meter as you tap your relays, if you tap a relay that gives you full power, it will save you the trouble of having to find it again.

The car will think it's immobilized and will not start if the engine control module does not see it's +15 at pin 58, who knows what thing it's thinking if it only sees 10 and it should probably see +12. Knowing that you have cranked it a few times without a successful start 10v might be all there is to see, so hook up a battery charger and run that charger at 50amps while you're checking voltages with the key on.
The WIS section on control module power supply tells us that the car will not start if the control module does not have power supplied from "Current (+30 Circuit)" supplied from MAXI fuses 2 & 28. The WIS section on control module power supply also refers to power from fuse 17 as "Current (+15 Circuit)" if fuse 17 is a 15 amp and MAXI fuses 2 & 28 are 30amp I would assume that the +15 of the coil test and +15 of the three circuit breaking are translation errors and the +12 battery voltage is actually the intended value and the battery charger should make sure that it will be present if it can be. With the battery charger in place check power at these fuses and check the coil again. If key on voltage is still low at the coil check every thing in the harness between the coil and ECM that you physically can.

To check for loose connectors on relay sockets gently move relay north south then east west and feel the movement, works good for the 4 pin sockets, 5 pin you need to remove from socket to test the pinch of the inner pin. These are female spade connectors and they can loose grip strength with heat and cool of the engine compartment over time.

To check for bad crimp connects and wires broken near the connection, gently pull on each individual wire, if it's a bad crimp the wire will pull free, if it's broken from flexing near the connection the insulation will stretch.

[Digger]

What are the typical things that will disrupt spark if a fault is dectected?

If there is anything in the Motronic 4.1 OBD2 that will disrupt spark with a detected fault, it's not mentioned in the controller operation overview. Even a bad Crank Position Sensor that has killed spark won't show a fault until the engine knows it's cranking and it doesn't see the signal. It is OBD2 compliant and an OBD2 code reader can pull codes from this controller. If you have any codes they could sure help, I'm looking at a pictoral flowchart of the controller power supply where the car battery picture is marked +30 and the associated schematic isn't complete, or the circuit contains components that serve no function. When I found this I found the 3 page schematic update for US market and lost it in the WIS. This 900 WIS seems to have a user hostile attitude.

[Pinnacleranch]

Thanks to Digger I finally got this Saab running. It turned out to not be any of the usual suspects. I replaced CPS, fuel pump and filter, coil, distributor, checked all grounds, and the problem turned out to be the ignition switch. Occasionally it would make spark for one crank then not the next and the motor would pop coming off cranking but not run. Replacing the switch is a big job as the entire console has to be disassembled but to my surprise the car immediately started up with the new switch. The connector inside the center console (not the ignition switch) is difficult to connect and at first did not connect properly so rear windows and sunroof didn't work but got that sorted out and all is fine. Thank you digger for all your help, good luck to you in the future.