Well, I've been through every Volvo forum I can find through Google on this intermittent issue set. I see a LOT of different possible caused from pumps to relays to the expected distributor cap/rotor check and various wiring wear. I've only begun trouble shooting it (since it's so intermittent) and figured I'd ask here for any insight too.

Details on car and problems:
1992 240 Automatic Sedan. Beautifully maintained and only 119K single-owner when I got it in 2009 (214K now).

A month or two ago, it started hesitating/lacking power when I would accelerate from a stop sign or traffic light. Seemed to happen most when I'd be gentle with the gas pedal (ie, not burn rubber). No problems when on highway, though. Then, after a night of cold & heavy rain, it wouldn't start at all. The engine cranked, the lights all worked, but no ignition. Replaced the fuses, cleaned the terminals. Tried without the AMM plugged in. Tried with no luck for an hour, finally towed it to a Volvo specialist. They said it started up just fine for them... when it had sat and dried out later that morning.

Had them replace the fuel pump relay anyway (was old) and repair a front-of-system exhaust leak (missing bolts). The tech couldn't feel the from-stop hesitation happening at all. They said the engine smelled like maybe it had run rich, but I wonder if that wasn't from me trying to occasionally crank the thing for an hour with no start and the pumps putting fuel into it every time? Ah, intermittent issues...

It seemed to work again for a month: cold mornings, wet mornings, after sitting, after running; no issues other than some squealing belt noise when cold. Then again today, after a cold rainy night, it would crank but not ignite. Finally gave it the gas pedal as I turned the key and it shuddered into idle, but almost stalled out at my first stop sign, before reengaging and driving fine. Drove to work, no other stalls or issues after the engine warmed up. Gas tank is near full.

I'm about 4K miles from the recommended plugs/wires/rotor tuneup, which is next on my troubleshooting. I've yet to check for tank pump function at the fuse box as I can't hear the pumps over city noise at the best of times. Also to-do.

Summary:
AMM (year-old) disconnect/limp home: no change during no-start
New Fuel Pump Relay
New Fuses
Fixed Exhaust Leak, ahead of Cat/Lambda sensor
6 mo. old battery

To Do:
Plugs/Wires & Rotor/Cap: check/replace
Test Tank and Main Fuel Pumps at fuse box

Any other advice from the combined wisdom?

 

next time it won't start, you need to determine if its fuel or spark, that narrows the problem space in half.

 

As you say pierce, have to check spark and fuel state. Since the original instance of this issue (before relay replacement) left the engine flooded, wouldn't it be lack of spark most likely?

I poked around at the new relay behind the footwell cover, and after driving it seemed somewhat warm. Is that expected? Not painfully hot, but definitely warmer than body temp. And it seems the bracket to hold my relay against the black module back there is missing... so the relay kind of just dangles. Would that cause issues down the road?

 

the fuel pump relay getting warm isn't surprising, hot would be bad. there's two relay coils in that package, one for the ECU and acccessory power, and the other for the fuel pump power. that relay hanging on its wire won't cause any problems as long as a passenger doesn't get tangled up in it or something.


late 92/93 240's have some wiring changes over earlier ones, for some reason Volvo decided to make major changes right at the end of production.

 

Thanks again. At least I won't worry over the warm relay and the unmounted aspect. No chance of a passenger messing with it. The footwell cover felt is solidly in place (on that side anyway).

Will update when I figure out more on the wet start issues.

 

Updates after thorough engine inspection:

Wire harness for the crank sensor is frayed, there's a vacuum leak at the hose to the fuel pressure regulator, and a crack in the spark rotor. Replacing them all this week.

The fuel pumps both give response when tested individually.

 

Final updates:

- The coil wire was definitely arcing, but I replaced all 5 wires & plugs, just in case.
- New crank position sensor
- New fuel pressure regulator and hoses
- New fuel injector relay (engine bay location)
- Distro cap and rotor actually look OK, so left alone for now

Also, stuff done for age's sake: new accessory mount bushings on all 3 items.

Car runs great!