What you are describing is an engine with little or no compression. It's got fuel, it's got spark but it has no fire. It will normally crank faster than usual. You've most likely got sticking exhaust valves due to being "flooded". The engine manager ment system, on your car the Jettronic (LH 3.2), the '93 and some early '94 850 had seperate injection and ignition systems. The problem was partially fixed in '94 by changing to the Motronic system wihich integrates both fuel and ignition systems. By the '95 model year, the 850s got redesigned exhaust valves and larger exhaust valve guides to prevent carbon deposits on the valve stems.
The LH system started and ran extremely rich until a short time after the engine reached operating temperature. The rich mixture would wash the oil off of the stems and guides for the exhast valves, hence the exhaust valves would get stuck open if the engine was turned off without reaching full operating temperature. I work at a dealership and we get calls from folks with this perdicament, mostly in the winter of on cold fall and sping days and mornings. The moved the car in the driveway or across the parking lot; it started and ran great, and now it won't start! There were also problems with exhaust valve deposits. Most often turbo cars, but normal asperated engines as well expirence
sticking valves. Turbo engines usually had oil being leaked into the intake air by the compressor side of the turbocharger, going into the engine and not being completely burnt and coking up on the stems of the exhaust valves. You end up seeing slightly blue but very white exhaust, which hangs in the air behind you for quite some time, of bluish white smoke when the car is first driven after a cold start.
Carbon is left on the stems of the exhaust valves because of the rich mixture during warm-up, . So much, the valves would hang up and get stuck on the valve guides. With the valves stuck you have no compression in any cylanders. During a cold start condition the injection system is dumping so much fuel into the mix to keep it full rich; the oil become fouled with fuel and becomes more like water. If you smell gas when you stick your nose over the filler cap, the oil should be changed before attempting to start it.
Volvo sent out a 2 bulleting pertianing to the early 960s and 850s with their recomendations to deal with the root causes. One is overbore the exhaust guides so the guides will tend resist hanging up the valves by the coked oil or carbon. There was also a tech note which directs you to change oil and filter using a synthetic which resists coking, even at extremely high temperatures. Most oil would turn in to a solid block of gook. After the oil change, you are to take the car out and beet the crap out of it in low gear for 20 to 30 miles. You need to maintain at least 4000 RPMs, even when stopped. It's best to take it out on the highway and hammer it down the road in low. This will get the valves turning, depressed and slammed shut. The idea is to get the valves to clean their seats and stems as much as possible You should also inspect the spark plugs, they sometimes bridge their gap with carbon. Either from incomplete combustion from the stuck valves or not getting hot enough to clean themselves. After that, hop in, floor it and crank away. Beleive me, it will start eventually!!! I've had to put a jump box or another vehicle while it was running just to crank it long enough to get it to start running on all 5 again. The car has to be run, preferably driven, the whole time to boil off any remaining contaminants in the oil and burn off any crap in the combustion chambers.
A thermostat that sticks intermittently, or is stuck open may cause this no start to be a regular occourance. The oil never gets a chance to boil off condensation or unburnt fuel, both are killers of connecting rod and main bearings. It causes a no start when the oil is so fuel fouled that so much gas vapor get sucked in through the crankcase ventilation or past the rings, the fuel/air mix is so rich combustion, if any, is far from complete. You end up smelling raw fuel from the tailpipe and a rough idle. In a volvo Tech Note explaining the cause of discolored engine oil in some cars. Condensation in the crankcase mixes with the detergent addatives in all approved oils, that is generally harmless, You get a bit of whipped and foamy oil on the filler cap and dipstuck. In older cars oil like that always meant an internal coolant leak inot the oil, and back when the oils started doing that, which was back in the early '90s Volvo warranties paid for a lot of head gaskets and motors, so when they started getting too many perfectly good engines back for remanufacture they figured out what the problem was. We've seen a number of engines that were blown beyond overhauling, spun bearings, thrown rods that took out a good size chunk of the block too. The owners made mostly short trips, often the cars were stone cold, and drive not even long enough to fully warm the car up. And far from long enough to get the oil hot enough to boil any moisture in it so it can escape via the PVC system. Starting a cold car and mooving it 20 feet then shutting it down is the worst thing you can do to an engine. Some people don't drive their card hard or put miles on so slowly, that they need more frequent oil changes. Yesterday we got a tow in, it's an 850, the customr thought he had coolant in his oil because he saw creamy stuff on his dipstick and filler cap. The last oil change the car had was only 200 miles ago, but that was almost 7 monthes ago!! For this fella he needs it changed every 3 monther, or he should walk!.
If you have any questions or need any Technical info, ask away.