1986 Mercury Grand Marquis Service and Repair Manual

This factory service and repair manual for the 1986 Mercury Grand Marquis sets two overhead-valve V8s — 5.0L, 302 cubic inches, and 5.8L, 351 cubic inches, both naturally aspirated on gasoline — against three bodies: a two-door sedan, a four-door sedan and a four-door wagon. Base, Colony Park and LS make up the trim ladder. The value of a factory book on a car this age lies in the exact figures it prints: ignition timing, running clearances and fastener torque, plus the wiring diagrams and diagnostic routines for the fuel, charging and lighting circuits.

Engines covered

• 5.0L V8 (302 cu in) — OHV, naturally aspirated, gasoline
• 5.8L V8 (351 cu in) — OHV, naturally aspirated, gasoline

Body styles covered

• 2-door sedan
• 4-door sedan
• 4-door wagon

Trims covered

• Base
• Colony Park
• LS

Known issues on the 1986 Grand Marquis. The federal record carries two recalls, both about fuel escaping where it should not. In one, a spring-lock coupling in the fuel line may never engage fully, so pressure, vibration and engine movement can pull it apart and spill gasoline near an ignition source. In the other, replacement pumps with poorly installed diaphragms can leak toward the same end. Owners have logged 21 complaints, ten on the electrical system, four on the engine and cooling system and two on the service brakes — fuel line service, circuit diagnostics and brake specifications are all covered here.