1987 420sel 120,000 miles. Difficulty starting after the car has been driven and warm. Let the car sit after its been driven and it cranks forever (15sec) before it starts. When the car is cold it starts better but not perfectly. The supply line to the distributor is producing enough volume. Please tell me it's a simple, yet more importantly, a cheap repair! Should I replace the fuel relay? It's not the ignition coil.