There seems to be some problem with the fuel tank vent which could have caused momentary high fuel pressure to get into the system.

The word "could" is important and merely suggestive.

Now I'll talk about the Check Engine light. The CEL doesn't necessarily mean a code has been set, although in 9 out of 10 cases it means exactly that. The other area that can set the CEL off is low engine speed. Also voltage issues resulting from low engine speed.

The low engine speed threshhold won't cause any codes since it's more an operational thing. If it set a code for that the CEL would be on in a lot more cars, a lot more frequently. The low voltage aspect is simply a result of having the engine not runnign enough to get the charging circuit up to par. There is a lot of load when the engine first starts and the engine computers judge all the signals. If something doesn't match, it sets the light only because something is amiss. For example, you wouldn't see a momentary CEL on the highway. But at a stop sign, if the engine stumbles you might see the CEL. I have a feeling that's what happened in this case and I would worry more about not being able to get gas into the tank than anything else.
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1992 940 wagon, very low miles
as well as others.