Basic Testing Mitsubishi Sigma pre-I

INTRODUCTION

The following diagnostic steps are here to prevent overlooking a simple problem. This is also the place to start diagnosis for a "NO-START" condition.

The first step in diagnosing any driveability problem is to verify that the problem exists. This may be accomplished by test driving the vehicle under the conditions during which the problem reportedly occurs.

Prior to entering self-diagnostics, a careful and complete inspection of several systems is required. Most driveability or "no-start" problems are not related to computerized engine control systems, but are in fact simple mechanical, electrical, fuel or vacuum related faults. Most engine control problems are the result of mechanical breakdowns, poor electrical connections or damaged or misrouted vacuum hoses.

Before considering the computer system as a possible cause of problems, ignition high tension wires, fuel supply, electrical connections and vacuum hoses should be checked. Failure to do so may result in improper diagnosis or lost diagnostic time.

VISUAL INSPECTION

Perform a visual inspection of all electrical wiring. Look for chafed, stretched, cut or pinched wiring. Inspect electrical connectors and connections for tight fit and corrosion. Repair as necessary. Inspect all vacuum hoses for proper routing, cuts or pinches. If necessary, see the VACUUM DIAGRAMS article to verify routing and connections. Repair as necessary. Inspect air induction system for possible vacuum leaks.

Compression

Engine mechanical condition can be checked using a compression gauge, vacuum gauge, or an engine analyzer capable of performing a relative compression test. See engine analyzer instruction manual for availability and description of relative compression feature.

Exhaust System Backpressure

The exhaust system can be checked with a vacuum gauge or a pressure gauge. Remove O2 sensor or air injection check valve. Connect a 1-10 psi gauge and run engine at 2500 RPM. If exhaust system backpressure is over 1.75-2.0 psi, exhaust system or catalytic converter is plugged.

If a vacuum gauge is used, connect it to intake manifold vacuum. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge slowly drops after stabilizing, exhaust system should be checked for a restriction.

FUEL PRESSURE

Basic diagnosis of fuel system should begin with determining fuel system pressure.

1. Ensure engine is at operating temperature. Disconnect fuel hose from carburetor. Connect a fuel pressure gauge to fuel hose end. Disconnect fuel return hose from fuel pump. Plug fuel pump return opening.
2. Start and run engine at 1250 RPM. Refer to the «FUEL PUMP SPECIFICATIONS»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing) table. Turn engine off. With fuel hose disconnected from carburetor, place hose end into a container. Leave fuel return opening in fuel pump plugged.
3. Start and run engine at 1250 RPM. Measure volume of fuel pumped in one minute. Refer to the «FUEL PUMP SPECIFICATIONS»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing) table. FUEL PUMP SPECIFICATIONS Application psi (kg/cm 2 ) Volume In One Min.: Pts. (L) Montero 2.8-4.2 (.19-.29) N/A Pickup 2.0L 2.7-3.7 (.18-.26) N/A 2.6L 2.8-4.2 (.19-.29) N/A Precis 2.8-3.6 (.19-.25) 1.7 (.80)

FUEL INJECTED ENGINES

1. On Montero, Sigma and Van/Wagon, disconnect fuel pump harness connector at fuel tank. On Starion, remove floor panel in luggage compartment. Disconnect electrical connector near fuel pump. On all models, start engine. Let engine run until it stops. Turn ignition off. Disconnect negative battery terminal. Connect fuel pump harness connector. CAUTION: Use a rag to cover fuel hose connection prior to loosening bolt as there may still be residual fuel pressure in system.
2. On 1.6L and 2.0L (DOHC), remove brace for access to fuel line. On all engines, disconnect high pressure fuel hose at delivery pipe. (Scheme 1) Connect hose Adapter (MD998742 ) (except Starion) and Adapter Hose (MD998709 ) (except Starion) to delivery pipe. On Starion, use Adapter (MD998700 ) for connection to injection mixer. On Montero, use Adapter (MD998700 ) and Adapter Hose (MD998753 ) for connection to delivery pipe. On all models, connect fuel hose to adapter. Connect a fuel pressure gauge to hose adapter. NOTE: On Sigma and Van/Wagon models, fuel hose adapter tool number is not available from manufacturer.
3. Connect negative battery terminal. Connect battery voltage to fuel pump test terminal. Refer to «FUEL PUMP TEST TERMINAL LOCATION»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing) table. Ensure no fuel leaks are present.
4. Start engine and idle. Measure fuel pressure with vacuum hose connected to fuel pressure regulator. Disconnect and plug vacuum hose from pressure regulator. Record fuel pressure readings. Refer to «FUEL PRESSURE SPECIFICATIONS»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing) table.
5. Raise engine speed to 2500-3000 RPM, 2-3 times. Ensure fuel pressure does not drop when engine returns to idle. Check for fuel pressure in fuel return hose by gently pinching hose while raising engine speed.
6. There will not be any fuel pressure in return hose if fuel volume is low. Turn engine off. If fuel pressure is lower than specification, check for a faulty fuel pressure regulator or fuel pump.
7. If fuel pressure is higher than specification, check for a faulty fuel pressure regulator or plugged fuel return line. If fuel pressure does not change when vacuum hose for regulator is connected or disconnected, check for a leaking vacuum hose.
8. Fuel pressure should not drop off. If fuel pressure drops suddenly, check for leakage in fuel pump. If fuel pressure drops slowly, check for leakage at injector. Remove fuel pressure gauge. Install a new "O" ring at end of high pressure hose.

Control Relay

This multi-purpose relay switches power to vehicle sensors and actuators including airflow sensor, crank angle sensor, idle speed control, injectors and fuel pump, (not all sensors are used on all engines). When ignition switch is turned "ON" position, ECU energizes coils controlling injectors, airflow sensor and idle speed control. When ignition switch is turned to "START" position, ECU energizes coils (through inhibitor switch on automatic transmission) to supply power to fuel pump. Relay failure will cause a no-start condition. For additional testing see appropriate SYSTEM/COMPONENT TESTS article. Refer to the following list

Scheme 1

1. Fuel Injected, see: I - «SYSTEM/COMPONENT TESTS - EFI»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#systemcomponent-tests-efi)
2. Carbureted, see: I - «SYSTEM/COMPONENT TESTS - CARBURETED»(ref-18793) FUEL PUMP TEST TERMINAL LOCATION Application Wire Color Location Galant Yellow/Green Left rear of engine compartment Starion Black/White Right front of engine compartment Van/Wagon Red/Green Left rear of battery compartment Montero Black/White Behind right kick panel Sigma Black/Blue Left rear engine compartment FUEL PRESSURE SPECIFICATIONS Application psi (kg/cm 2 ) Regulator Hose On All Engines 38 (2.7) Starion 35-38 (2.5-2.7) Regulator Hose Off All Other Models 47-50 (3.3-3.5) Montero 47-53 (3.3-3.5)

Spark (All Engines)

Check for spark at coil wire (if applicable) and at each spark plug wire using a high output spark tester. Check spark plug wire resistance on suspect wires. See SPECIFICATIONS article.

Ignition Coil Resistance

1. Using a DVOM, measure primary resistance between connector terminals No. 2 and No. 4 (coils for cylinders No. 1 and No. 4). Measure primary resistance between connector terminals No. 4 and No. 1 (coils for cylinders No. 2 and No. 3). (Scheme 2)
2. Disconnect ignition coil connector. Measure secondary resistance between coil towers for cylinders No. 1 and No. 4. Measure secondary resistance between coil towers for cylinders No. 2 and No. 3. (Scheme 2)- see scheme 7. Refer to the «DIS IGNITION COIL RESISTANCE»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing) table.

Power Transistor

1. Remove connector from power transistor. Using a DVOM, place positive lead to terminal No. 4 and negative lead to terminal No. 6. (Scheme 7) Ensure there is no continuity.
2. Using one 1.5 volt dry cell battery, connect positive end of 1.5 volt battery to transistor terminal No. 5 and negative end of 1.5 volt battery to transistor terminal No. 4. Place positive lead of DVOM to terminal No. 4 and negative lead to terminal No. 6 to ensure continuity is present.
3. Connect positive end of 1.5 volt battery to transistor terminal No. 2 and negative end of 1.5 volt battery to transistor terminal No. 4. Place positive lead of DVOM to terminal No. 4 and negative lead to terminal No. 1 to ensure continuity is present. If DVOM does not respond properly, replace power transistor.

Crank Angle Sensor

See FAULT CHARTS-PFI in TESTS W/CODES article.

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

DIS IGNITION COIL RESISTANCE - Ohms @ 68°F (20°C)

Using a DVOM, measure primary resistance between positive and negative terminals of coil. (Scheme 2)- see scheme 7. Measure resistance between coil positive terminal and ignition coil tower. Refer to the IGNITION COIL RESISTANCE table.

Power Transistor (Fuel Injected Models)

1. Remove connector from power transistor. Using a DVOM, place positive lead of ohmmeter to terminal No. 2 and negative lead to terminal No. 3. (Scheme 7) Ensure there is no continuity.
2. Using a 1.5 volt dry cell battery, connect positive end of 1.5 volt battery to transistor terminal No. 1 and negative end of 1.5 volt battery to transistor terminal No. 2. Place positive lead of DVOM to terminal No. 2 and negative lead to terminal No. 3 to ensure continuity is present. If DVOM does not respond properly, replace power transistor.

See TESTS W/CODES article.

Scheme 7

IGNITION COIL RESISTANCE - Ohms @ 68°F (20°C)

IGNITION COIL RESISTOR

IGNITION COIL RESISTOR RESISTANCE @ 68°F (20°C)

VACUUM ADVANCE DISTRIBUTOR SPECIFICATIONS

1. With engine at operating temperature, disconnect vacuum hose from distributor. Run engine at idle.
2. Using an advance timing light, check ignition timing. Raise engine speed to specified RPM. Check ignition timing. See the «DISTRIBUTOR ADVANCE SPECIFICATIONS»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing) table.
3. Connect a vacuum pump to distributor advance unit. With engine running at idle, apply specified vacuum to advance unit. Check ignition timing. See the «DISTRIBUTOR ADVANCE SPECIFICATIONS»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing) table. DISTRIBUTOR ADVANCE SPECIFICATIONS (1) Application Centrifugal Degrees @ RPM Vacuum Degrees @ In. Hg Starion 2.6L 0 @ 1200 0 @ 3.15 2.6L 10 @ 2000 12 @ 5.91 2.6L 33 @ 6000 23 @ 11.01 Raider 2.6L (2) 0 @ 1600 0 @ 3.15 2.6L 9 @ 2800 8 @ 5.91 2.6L 19 @ 6000 20 @ 14.17 Pickup 2.0L California Models (2) Man. Trans. 0 @ 1200 0 @ 3.15 Man. Trans. 12 @ 2800 12 @ 5.91 Man. Trans. 20 @ 6000 23 @ 11.01 Auto. Trans. 0 @ 1200 0 @ 3.15 Auto. Trans. 12 @ 2800 8 @ 5.91 Auto. Trans. 20 @ 6000 20 @ 14.17 Federal Models Man. Trans. 0 @ 1200 0 @ 3.15 Man. Trans. 12 @ 2800 12 @ 5.91 Man. Trans. 20 @ 6000 23 @ 11.01 Auto. Trans. 0 @ 1200 0 @ 3.15 Auto. Trans. 12 @ 2800 8 @ 5.91 Auto. Trans. 20 @ 6000 20 @ 14.17 Precis 1.5L 0 @ 1500 0 @ 3.15 1.5L 5 @ 2500 N/A 1.5L 16 @ 6000 (3) 23@ 14.17 (1) Advance specifications for models not listed are computer controlled. (2) Idle advance on Calif. and High Alt. models is 0 degrees @ 2.36 in. Hg and 5 degrees @ 3.15 in. Hg. (3) Vacuum advance on Federal man. trans. models is 23 degrees @ 11.02 in. Hg.

IDLE SPEED & IGNITION TIMING

Note. If engine is equipped with a dual diaphragm distributor, vehicle will not have an ignition timing adjustment connector.

1. Ensure vehicle is at operating temperature, all accessories are off and transmission is in Park or Neutral. Vehicle front wheels must be in straight-ahead position and curb idle speed set to specification. If vehicle is equipped with a dual diaphragm distributor, go to next step. If vehicle is equipped with an ignition timing adjustment connector, go to step 3).
2. Disconnect vacuum hose farthest from distributor. Plug vacuum hose. Check basic ignition timing. Connect vacuum hose to distributor. Check actual ignition timing. Refer to the «IGNITION TIMING»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing) table.
3. Ground ignition timing adjustment connector. Refer to «IGNITION TIMING ADJUSTMENT CONNECTOR LOCATION»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing) table. Check basic ignition timing. Disconnect ground wire on ignition timing adjustment connector. Check actual ignition timing. Refer to the «IGNITION TIMING»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing) table. IGNITION TIMING (Degrees BTDC @ RPM) Application (1) Basic (2) (3) Actual 1.5L Precis Federal 5 @ 650-850 N/A California 3 @ 650-850 N/A Mirage 5 @ 650-850 15 @ 650-850 1.6L Mirage 5 @ 650-850 8 @ 650-850 2.0L Galant & Pickup 5 @ 600-800 (4) 10 @ 600-800 2.4L Van/Wagon 5 @ 650-850 8 @ 650-850 2.6L Starion 10 @ 750-950 15 @ 750-950 Montero & Pickup 7 @ 750-950 12 @ 750-950 3.0L Montero & Sigma 5 @ 600-800 15 @ 600-800 (1) With ignition timing adjustment connector grounded or vacuum hose (farthest from dist.) disconnected. (2) With ignition timing adjustment connector ungrounded or vacuum hose (farthest from dist.) connected. Ignition timing may fluctuate. (3) If altitude is more than 2300 ft. above sea level, actual timing may be advanced. (4) Actual ignition timing on Galant Dual Overhead Camshaft (DOHC) engine is 12 degrees. IGNITION TIMING ADJUSTMENT CONNECTOR LOCATION (1) Application (2) Wire Color Location Starion Red/Yellow Right front of engine compartment Galant White/Yellow Left rear of engine compartment Mirage Yellow/Red Middle of firewall Montero White/Yellow Left rear of engine compartment Sigma Black/Blue Front of left shock tower Van/Wagon Silver Rear center of engine compartment (1) Remove waterproof female connector (if equipped) for access to wire. (2) This wire in connector is grounded for basic timing adjustment.

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to the TESTS W/CODES article. If no hard codes are found during self-diagnostics, proceed to the TESTS W/O CODES article for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.), or intermittent diagnosis procedures.

See also:
• SYSTEM/COMPONENT TESTS - EFI
• SPECIFICATIONS
• TESTS W/CODES
• TESTS W/O CODES
• FUEL PUMP SPECIFICATIONS