A hopefully accurate drawing is in the relay section of the 700/900 series FAQ. It is supposedly the leftmost relay in the second row. This is marked "Continuous Injection" in the Haynes manual, which makes sense.

Let me note that this is just a small flaw in the Haynes manual. Other areas are much more accurate, for instance the interior panel removal procedure for post-1984 doors, or the headlamp replacement procedure. I also enjoyed it's comments on the reliability of the B28F engine.

Back to the topic, if you're not familliar with the relay panel, it is located behind the ashtray, above the fuse panel. You can access both by pushing the marked bar on the bottom of the ashtray upward while pulling outward on it. This will reveal the fuse panel in all her glory. When it comes to accessing the relays, I have found it neccesary to remove the cigarette lighter and coin tray as well. This is accomplished by pulling the trim from around the lighter outlet, and removing the two screws revealed. If you're sporting a 760 radio with the graphic EQ, you may just want to shrink your hands.

I hope that this helps, and that the relay is your problem, and not something more severe. Do remember that all bricks go to heaven.
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89 760 GLE 150k/ 86 740 GLE 240k -- Still going.