Volvo Repair: 1990 volvo 740 turbo/innercooler, flash flash flash, example 121

Question
This Volvo runs great, uses no oil and gets 26.8 mpg. Highway. 22 city. With 225,000 miles on it. I keep it on a good maintenance schedule. Replaced the computer five years ago. It is a manual transmission. It has started shutting down for a second or two when I am driving it, then restarts on it own and runs fine. Yesterday it quit while waiting on a red light to change. It was hard to get restarted. Had to try several times, thank god for a good battery. It started and ran o.k. for about a mile or two, and shut down again, then restarted on its own. I had this before and it was  water in the fuel. I put in a water removal chemical and that solved the problem. I am in Pensacola Florida, and water in the gas is common here in the summer. I am trying the water removal chemical again. Is there anything else I need to be looking for, or; expecting? Any help would be greatly appreciated......Thank you.
Don

Answer
I would first check for any codes in the fuel and ignition system.below is how to check them.



in the engine bay on the drivers side near the strut tower there is a small black box with a wire attached to it.place the wire in the terminal marked 2.turn ignition key on (not started)press the small button for 1 second and the code will be displayed as a series of flashes.a red led displays the codes.the code will be three digits.small pause in between flashes for a single number long pause between flashes for the next number.example 121 will be flash.....flash..flash.....flash.repeat three times or until first code repeats itself.to erase the code after all codes have been checked hold the button for a good 5 seconds then release the light should light steady,then press for another 5seconds.this will erase the codes.  email me the codes and i will tell you what they are..socket 2is the fuel system 6 is ignition.