Just bought a '94 940 turbo, drove it a couple hundred miles home from Pennsylvania to Virginia without any trouble. The next day I take it to run some errands and it starts rough, and idles high initially. Once its warmed up it runs fine. I go to the store and by the time I come back out it won't start anymore. I manage to get home and grab my tools and it looks like it doesn't have any spark (cranked with a timing light hooked up to the coil wire: nothing).


the solenoids em1 and em2 both close on start and the engine turns over fine. I get ~12v on terminal 15->grnd on the coil with the key in kp2. originally I had .2VAC on the connector for terminal 1 when cranking (slightly out of bounds but close to what is listed in the guide) so I replaced the coil, nothing. Since the coil wasn't the problem I went ahead and replaced the power stage, this worked! the car started right up, idled a bit rough and fast at first then smoothed out. I did a few restarts to make sure everything was okay then drove her home.

This morning I go to start the car and no start again. Same as before, turns over fine, but no spark. I run through the same checks as before, it looks like the power stage again, I swap it out for the old unit, and the car starts up again (still with the high rough idle that smooths out soon). I drive a couple blocks and park the car. Just to check I try the new power stage again, and the car still starts and runs fine.

At noon I go to check and see if its still running, and nope. once again no start no spark. I try swapping out the power stages again, and it does nothing. I go through the checks again and terminal 1 is now at .07-.01 VAC on crank.

The only anomaly I can find is that the resistance between terms 1 and 4 on the powerstage connector is 45k ohms instead of 1 ohm. checking the connection it looks like the red/white wire from terminal 1 (on powerstage) to terminal 1 on coil is fine, minimal resistance, but the connection between terminal 4 and the coil has the high resistance. both connections get 12v on kp2 Looking at the wiring diagrams it doesn't look like the blue wire from the power stage is the same as the blue wire from coil. am I doing this test wrong? am I missing something obvious?


for reference I'm using http://stepbystepvolvo.com/NoStart.html to diagnose

Any help would be appreciated