Contrary to a lot of conventional wisdom, the sole purpose of that check valve is to aid hot starts—rather than to hold pressure overnight.

The theory is that by maintaining some pressure for a short time (the "residual pressure" spec is measured in minutes ), it will prevent the vapor lock that might result from fuel boiling in the injector rail, due to heat soak from the hot engine.

Back by the fuel pump is a oneway valve to keep the fuel in the line after the car is turned off. If this valve goes bad, it may take a longg crank to get the fuel pressure back up.

Klaus
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I still miss my 164 and my 854T. Just driving a V70R :)

Check the crank postion sensor. This is normally a problem when the engine is hot but can also be problematic when cold. If there is no signal or a weak or degraded signal from the("Hall effect" sensor which picks up the flywheel teeth location) the main computer will be hit or miss on starting!

This is a $30 part and somewhat easy to repair (except for the samll bolt that holds the sensor to the aluminum bell housing) tight fit and difficult to reach.)

The other PM's noted should also be checked but I would bet on the CPS

How are your Spark Plugs, Wires, Distributor Cap and Rotor?

If you haven't replaced them in a while, now might be the time. And while you're at it, you might want to clean your Throttle Body, and replace/clean the Flame Trap with the throttle body out of the way.

Also it might be time to change the fuel filter, especially if your Fuel Pump is really loud. Let some pressure accumulate in the Fuel Rail by waiting with the ignition on before starting her up, might help.

If you are experiencing difficulty starting after a drive (when the engine is still hot) you may want also check the Thermostat on the Airbox as they go bad often and let the engine suck hot air off of the Exhaust Manifold. This could also fry your Air Mass Meter over time which can be pricey to replace.

Last but not least, I have an '89 244, and I am lucky not to have any corrosion on the 25a fuse holder in the engine compartment by the battery. You might want to check yours, although corrosion usually leads to a no-start situation.

Good Luck,

Justin