* Under the hood in the fuse box: This is the most likely location. The fuse box might be under a cover, and the relay itself may be labeled or visually identifiable (it will usually be a larger, square-ish relay).
* Under the dashboard: Less common, but some models might have relays located here, often in a secondary fuse box.
* In the trunk (rare): While very unlikely for the fuel pump relay specifically, some related relays might reside in the trunk area.
To find it reliably:
1. Consult your owner's manual: This is the best starting point. Look for diagrams of the fuse box(es).
2. Use a wiring diagram: A wiring diagram for your specific 1988 Mercury Grand Marquis will show the fuel pump relay's location and the circuit it's part of. You can often find these online through automotive parts websites or repair manuals.
3. Visual inspection: Once you've located the fuse boxes (underhood and potentially under dash), carefully inspect the relays. They are usually square or rectangular and might have markings. You may need to remove a cover to see all of them.
WARNING: Before working on any electrical components, always disconnect the negative battery terminal to avoid electrical shocks or short circuits.
