Volvo Maintenance Hints for 7xx/9xx - Bill Garland's Nuclear ...

falls back into place. I once broke the ground wire to my alternator and that
caused the engine to quit, though it did sputter a little. The wire was broken in
the middle and once I pulled over and the car was still, I had good ground, but
once moving, it would make intermittent contact
Have you checked the fuel pump relay? Similar symptom to yours and seems to
be a fairly common problem among Bricksters. A bad/weak coil in my
experience shows up as consistent poor performance under high spark load
conditions, such as starting and large throttle openings at low RPMs. I check
the coil by removing the coil wire at the distributor and firmly locating (not
holding unless with insulated pliers) the the wire's tip about 3/8 inch from a
block or frame ground point. The spark should be a "thick" blueish white and
easily jump the 3/8" air gap with the engine being cranked by the starter. A
weak spark tends to be "thin" pinkish and sensitive to proximity to ground. The
normal arcing voltage (engine running) is in the 12-15 KV range for my '82 B21F
LH1.
I have had the similar problem on a 84 GL and found that the ignition pick-up
coil in the distributor was faulty. When the pick-up got warm the resistance in
the wire showed an open circuit and when it cooled off it was normal again. I
replaced the pick-up and problem was solved.
I had such a condition on an '83 245 twice once it turned out to be fraying wiring
harness right between the rear of the engine and the firewall and once it turned
out to be the computer on the inside of the right front fender.
See the FAQ section on Grounds for information about engine and chassis
ground maintenance.
Engine Cuts Out at Speed: Ignition Power Stage Failure. [Inquiry:] My 1990 740
GL Wagon (186,000 miles) stalls intermittently with the tachometer immediately
dropping to zero. It does it while cruising on the highway or while idling. I'm able to
restart it sometimes with the clutch if I'm moving along, otherwise with the key after I
get to the side of the road. If it sits for a few minutes that seems to help in restarting. It
appears that all other electrical components are not affected when this happens (radio
works, blower, flashers, etc.). It now happens almost daily, but started months ago
happening 1-2 times a month, then 1-2 times a week, etc. It's getting worse. My
mechanic has replaced some likely components: FP relay (behind fuse box), radio
relay (on the coolant reservoir) and crank sensor (with the white band - I had replaced
this at 90K as well). I also had a cracked distributor cap that was replaced. Plug wires
are in good shape. [Another similar case:] My symptoms were, the tach dropping to
zero and then the engine would bump start at speed and at a stop the car would
shudder and then die unless the motor is revved up at a stop to bump start the car.