My normally reliable 94 940 wagon (267,000) has now become unreliable.
It all started 3 weeks ago when it would not start. Quick fix - starter replaced.
Since then, the car abruptly shuts off while driving. It starts right back up again and will run smoothly until it shuts off again.
Distributor cap is intact-no cracks, all grounds are tight, wires all tight, replaced the suppression resistor, fuel pressure and pump are normal. Don' t think it's the crank sensor as it fires right up immediately.
Any ideas?

Two key questions:

Does the tach immediately drop to 0 when it dies or does in kind follow the engine speed down.

Does it pretty much immediately restart, first crank, after a couple of minutes of cool down...then die again after you get going for a while.

My tac goes to zero. while doing 65 I will just slowly pull off to the side and within 10 sec it comes back on. BTW auto transmission> I think it is either the CPS or power stage.

Dear DBC,

Hope you're well. When was the Crank Position Sensor (CPS, aka Crank Sensor) last changed? If it is the factory-original item, it is long past the end of its service life. See the FAQs for a procedure to change this item.

Based on reading several years of Brickboarders' posts, ignition power stage failure usually are heat-driven, i.e., failure is more common when ambient temperatures are high.

Hope this helps.

Yours faithfully,

Spook

I was actually leaning toward the system relay (fuel pump relay)...and still am. On my old 760 (turbo) I left the cover off the relay and you could here it click...hold the contacts together and it would IMMEDIATELY start running again.

it sounds like a cps that is losing continuity where the cable enters the sensor body. vibration is causing it to short.

i had a very similar experience with a car that would start and run and then just shut off. it took quite a while to settle on the cps as the problem.

Trust me, I struggled with this problem. It is the crank position sensor on the back of the distributor near the firewall. I replaced coil, wires, rotor etc. before I found a tiny crack in the wire. Not too hard to overlook, not to hard to replace. I agree with trichard & Amarin thanks for the help you've given me in the past.

Jeff
940gl
s70glt
240 maybe?

Sounds electrical to me.

Simple - What is the condition of the spark plug wires and coil wire? Have you tested them for arcing? Check the cap too. Pop the cap and look at the rotor's condition.

My next step would be to check the coil and the power stage. At 267K it is possible they might be done. Check the coil and power stage connections for tightness. Also look for corrosion, signs of burning and arcing. You can also test them for proper electrical output.

As mentioned, any OBD codes? CPS wire insulation okay?

--
Current - 95 855 GLT Sportwagon 255k, Formerly - 90 244 DL 300k

Hi 940fyrman,

Have a look at the crank sensor (CPS) at the back of the engine. Inspect if its cable is hardened, look for insulation cracks, etc.

Have you checked the OBD codes? Usually the OBD is sensitive enough to capture CPS fault.

Regards,
Amarin.