Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSPLYMOUTH1984HORIZON BASE, 1.6 AREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 10 (ENGINE CONTROLS - BASIC TESTING)FUEL SYSTEMFUEL PUMP & FUEL PRESSURE REGULATOR TEST2.2L, 2.5L TBI & 3.0L
1984 Plymouth Horizon Base, 1.6 A
2.2L, 2.5L TBI & 3.0L
1984 Plymouth Horizon Base, 1.6 ASECTION 2.2L, 2.5L TBI & 3.0L
WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 Plymouth Sundance, 1994 Plymouth Acclaim, 1994 Eagle Vision, 1994 Dodge Spirit, and 1994 Dodge Shadow. However, it is still accessible from the selected car via links, so may be relevant.
- Relieve fuel pressure. See appropriate RELIEVING FUEL PRESSURE procedure under FUEL PRESSURE. On 3.0L, disconnect vacuum hose from fuel pressure regulator before checking fuel pressure.
- On 2.2L and 2.5L TBI, fuel pressure regulator is not vacuum assisted. On all engines, disconnect fuel supply hose quick-disconnect connector from chassis lines at engine. Connect Fuel Pressure Gauge (C-4799) to Fuel Pressure Test Adapter (6539). Install adapter between fuel supply hose and chassis fuel line.CAUTION: DO NOT activate fuel pump for long periods, or engine may hydrostatically (liquid) lock.
- Using Diagnostic Readout Box (DRB), turn ignition switch to ON position. Select ASD FUEL SYSTEM TEST mode. In this mode, DRB energizes Auto Shutdown (ASD) relay, causing fuel pump to activate and pressurizing fuel system.
- Note fuel pressure, and record reading. Relieve fuel pressure. Remove fuel pressure gauge. If fuel pressure is within specification, fuel system is functioning properly and further testing is not required. See FUEL SYSTEM PRESSURE SPECIFICATIONS table.
- If fuel pressure is greater than specification, go to step 8). If fuel pressure is less than specification, install Fuel Pressure Gauge(C-4799) and Fuel Pressure Test Adapter (6539) in fuel supply line between fuel tank and fuel filter.
- Repeat ASD FUEL SYSTEM TEST. If fuel pressure is at least 5 psi greater than fuel pressure recorded in step 4), replace fuel filter. If no change is observed, gently squeeze fuel return hose.
- If fuel pressure increases while squeezing fuel return hose, replace fuel pressure regulator. If fuel pressure does not change while squeezing fuel return hose, problem may either be a plugged fuel inlet strainer or defective fuel pump. Repair as necessary.
- Disconnect fuel return hose from fuel pump at fuel tank. Connect Fuel Pressure Test Adapter (6541) to fuel return hose. Place other end of adapter into an approved 2 gallon gasoline container.
- Turn ignition switch to ON position. Repeat ASD FUEL SYSTEM TEST. If pressure is now correct, replace fuel pump assembly. See FUEL SYSTEM PRESSURE SPECIFICATIONS table. If pressure is still greater than specification, deactivate fuel pump. Remove fuel pressure test adapter, and connect fuel pump return hose.
- Disconnect fuel return hose from chassis fuel lines at engine. Connect Fuel Pressure Test Connector Adapter (6541) to fuel return hose. Place other end of hose in an approved gasoline container. Repeat ASD FUEL SYSTEM TEST.
- If pressure is now correct, check for restricted fuel return line. If no change is observed, replace fuel pressure regulator.
FUEL SYSTEM PRESSURE SPECIFICATIONS
| Application | (1) psi (kg/cm2 ) | ||
|---|---|---|---|
| 2.2L & 2.5L TBI | 39 (2.7) | ||
| 2.5L Flexible Fuel & 3.3L | 55 (3.9) | ||
| 3.0L & 3.5L | 48 (3.4) | ||
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WARNING:
Perform fuel pump test with fuel tank at least half full. Before disconnecting fuel line, relieve fuel pressure.
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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.