Compression
Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions. To check engine compression with a compression gauge, bring engine to normal operating temperature. Disconnect cold start injector (if equipped). Disconnect distributor electrical connector(s). Remove spark plugs. Disconnect air intake hose from throttle body. Fully open throttle. Ensure engine cranking speed is at least 250 RPM when measuring compression.
| Application | Specification |
|---|---|
| Compression Ratio | 10.5:1 |
| Compression Pressure | 185 psi (13.0 kg/cm 2 ) |
| Minimum Compression Pressure | 156 psi (11.0 kg/cm 2 ) |
| Maximum Variation Between Cylinders | 14 psi (1.0 kg/cm 2 ) |
COMPRESSION SPECIFICATIONS
Exhaust System Backpressure (Using Pressure Gauge)
Remove Oxygen Sensor (O2S) or air injection check valve (if equipped). Connect a 0-5 psi pressure gauge and run engine at 2500 RPM. If exhaust system backpressure is greater than 1 3/4 - 2 psi (.12-.14 kg/cm 2 ), exhaust system or catalytic converter is plugged.
Exhaust System Backpressure (Using Vacuum Gauge)
Connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, check for restricted exhaust system.
FUEL SYSTEM
| WARNING | Always relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components. |
FUEL SYSTEM PRESSURE RELEASE
Remove trunk trim panel and unplug fuel pump connector. Start and run engine until it stops. Wrap fuel line connection at fuel rail with shop towel to catch any spilled fuel. Loosen flare nut or banjo bolt enough to relieve any remaining fuel pressure. Tighten flare nut or banjo bolt.
- On front end of air intake chamber.
FUEL PRESSURE
- Ensure a sufficient amount of fuel is in fuel tank and battery is charged. Turn ignition off. Connect a jumper wire between terminals +B and FP of DLC No. 1. (Scheme 30) Turn ignition on. In engine compartment, grasp fuel hose leading from fuel filter.
- Fuel pressure should be felt in hose and fuel return noise should be heard. Turn ignition off. If fuel pressure is evident, go to next step. If fuel pressure is not evident, check fusible links, fuses, SFI main relay, fuel pump, PCM and wiring connections.
- Disconnect negative battery cable. Wait at least 90 seconds for air bag back-up power supply to be depleted. Connect fuel pressure gauge to fuel line fitting (banjo bolt) at: Fuel filter outlet.
- Ensure ignition is off. Reconnect negative battery cable. Connect a jumper wire between terminals +B and FP of DLC No. 1. (Scheme 30) Turn ignition on, with engine off. Check fuel pressure.
- If fuel pressure is 38-44 psi (2.7-3.1 kg/cm 2 ), go to next step. If fuel pressure exceeds specification, replace fuel pressure regulator. If fuel pressure is less than specification, check fuel hose and connections, fuel pump, fuel filter, fuel pressure regulator and injectors. See «SYSTEM/COMPONENT TESTS»(ref-21745) article.
- Disconnect jumper wire from DLC No. 1. Start engine. Disconnect and plug vacuum hose at fuel pressure regulator. With engine idling, check fuel pressure. See «FUEL PRESSURE SPECIFICATIONS»(ref-21759-S21955067782001010300000) table. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, check vacuum hose and fuel pressure regulator.
- Reconnect vacuum hose to fuel pressure regulator. With engine idling, check fuel pressure. See «FUEL PRESSURE SPECIFICATIONS»(ref-21759-S21955067782001010300000) table. If fuel pressure is not within specification, check vacuum hose and fuel pressure regulator.
- If fuel pressure is within specification, turn engine off, noting fuel pressure. If fuel pressure remains greater than 21 psi (1.5 kg/cm 2 ) for at least 5 minutes after engine is turned off, fuel pressure is okay. If fuel pressure decreases to less than 21 psi (1.5 kg/cm 2 ) within 5 minutes, check fuel pump, fuel pressure regulator and fuel injectors. See «SYSTEM/COMPONENT TESTS»(ref-21745) article.
| Application Type | At Idle With Vacuum | At Idle Without Vacuum |
|---|---|---|
| ES300 | 33-38 (2.3-2.7) | 38-44 (2.7-3.1) |
FUEL PRESSURE SPECIFICATIONS
Scheme 30
IDLE SPEED & IGNITION TIMING
Ensure idle speed and ignition timing are set to specification. See IDLE SPEED SPECIFICATIONS and IGNITION TIMING SPECIFICATIONS tables. For adjustment procedures, see appropriate ADJUSTMENTS article.
| CAUTION | DO NOT ground DLC terminal IG-. Damage to ignitor and/or ignition coil may result. Ensure tachometer is compatible with this system before use. |
SUMMARY
If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to TESTS W/CODES - OBD-II article. If no hard codes are found in self-diagnostics, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.