'82 240 d24 stalling- frustrated new owner

[Max]

Hello, all. just bought an 82 volvo 240 with d24. Car runs well while cold, but after 10 minutes or so, begins to surge and has no power, flat and then begins stalling withload, but will start and idle. Then after10 minutes or so will start with powerandthen will do the same routine within a minute or so. Frustrated! Compression checks fine, thermostat replaced, fuel clean.
Are there two fuel pumps? or one?