Bob --

The pre-'83 240s used different fuel pump relays. Generally, they're located just above the driver's left knee, above the cardboard kickpanel near the steering column. I had to resolder the fpr on my '82, and I suspect it's the same relay used in your '81.

It's either red ot green or blue or brown or something like that -- not white.

In a pinch, you can entirely bypass the relay by jumping fuses 5 & 7. This will force both pumps to run even if the key is off. I drove my '82 25 miles home this way by using a paper clip across the fuse clips (5 to 7). This is not safe, so use it only as a diagnostic.