1987 Plymouth Horizon AutomaticFACTORY OEM SERVICE PROCEDURE

Preliminary Fuel Tests

  1. Connect fuel pump pressure tester to fuel line at carburetor. Crank engine for 10 seconds. Fuel pump pressure should be 1-4 psi. If pressure is okay, check carburetor inlet circuit and repair as necessary.
  2. If pressure was not to specifications, connect fuel pressure tester to fuel line before fuel filter. Crank engine for 5 seconds. Fuel pressure should be 1-4 psi. If pressure is now okay, replace fuel filter.
  3. If pressure is still not to specifications, connect a vacuum gauge to the fuel pump inlet line. Disconnect the outlet fuel line from the fuel pump. Crank engine for 10 seconds. Vacuum gauge should read at least 10 in. Hg. If vacuum is okay, check for restricted fuel lines, improper fuel tank venting, and defective tank filter. If vacuum is not to specifications, replace fuel pump.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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