Volvo 850 Turbo Engine Troubleshooting Without Codes
Contents
1. nsure ignition timing and fuel pressure are correct heck fuel injectors nsure timing belt is not broken heck ground connections on intake manifold for control unit nd power stage nsure ignition coil resistance is correct nsure rotor distributor and plug wires are okay heck ignition control unit heck coolant temperature sensor and connector heck throttle switch and connector heck fuel control unit heck engine speed sensor or Hall Effect sensor turbo nsure power stage receives signal from ignition control nit heck airflow sensor if applicable QsW aqgQaQaQahhAw aQamanmaahs Difficult To Start When Hot nsure fuel pressure is correct heck for gasoline in oil nsure fuel injectors are not leaking heck ignition and sensor wires for proper connection nsure spark plugs are not fouled heck ignition and coil circuit heck engine speed sensor or Hall Effect sensor turbo heck throttle switch and connector heck idle valve Ensure airflow arrow points in correct direction QaegaqagnAnAaAEr POOR DRIVEABILITY Poor Idling Check throttle switch and connection Check coolant temperature sensor and connection Check idle air valve Check air temperature sensor and mass airflow meter FF FF FF HF HF F FF F F F F heck coolant temperature sensor n2. H TESTS W O CODES TURBO 1995 Volvo 850 1995 ENGINE PERFORMANCE Volvo Trouble Shooting No Codes 850 Turbo INTRODUCTION Before diagnosing symptoms or intermittent faults perform steps in the F BASIC TESTING TURBO article and procedures in the G TESTS W CODES TURBO article Use this article to diagnose driveability problems existing when a hard fault code is not present NOTE Some driveability problems may have been corrected by manufacturer with a revised computer control unit Check with manufacturer for latest computer application Symptom checks can direct the technician to malfunctioning component s for further diagnosis A symptom should lead to a specific component system test or adjustment Use intermittent test procedures to locate driveability problems that DO NOT occur when the vehicle is being tested These test procedures should also be used if a soft intermittent trouble code was present but no problem was found during self diagnostic testing NOTE For specific testing procedures refer to the I SYSTEM COMPONENT TESTS TURBO article For specifications see the D ADJUSTMENTS TURBO article or the C SPECIFICATIONS TURBO article SYMPTOMS SYMPTOM DIAGNOSIS When a diagnostic code cannot be confirmed or problem cannot be confirmed in the F BASIC TESTING TURBO article find basic symptom For example vehicl ngine will not
3. e heck coolant temperature sensor heck ignition and sensor wires for proper connection heck fuel injectors heck throttle switch and connector heck engine speed sensor or Hall Effect sensor turbo C C C C C C Knocking Check ignition and coil circuit Ensure spark plugs fire strong Blue White spark Check knock sensor Check throttle switch and connector Check ignition and coil circuit Check heck ngi fuel ne speed sensor or Hall Effect sensor Engine Misfire heck heck heck heck heck heck igni igni for inta thro injectors turbo tion and sensor wires for proper connection tion and coil circuit gasoline in oil ke and exhaust system ttle switch and connector for vacuum leaks FH FF OOO OOOO heck ngi ne speed sensor or Hall Effect sensor Insufficient Engine Power heck fuel injectors nsur heck heck heck heck fu airf for cool air l pressure is correct low sensor if applicable restricted exhaust ant temperature sensor temperature sensor heck heck heck ngi thro igni ne speed sensor ttle switch and connector tion and coil circuit heck heck FF HF HH F CP Cy eee Cy Oy OC O A A Poor F heck nsure heck heck heck ngi inta uel for spa for thro for ne speed sensor or Hall Effect sensor ke and exhaust sys
4. ircuit resistance Status changes on DVOM during test procedures indicate area of fault TEST PROCEDURES Intermittent Simulation Monitor circuit component voltage or resistance while using the following procedures to simulate an intermittent fault If engine is running check for self diagnostic codes Use test results to identify a faulty component or circuit Lightly vibrate component Heat component Wiggle or bend wiring harness Spray component with water mist Remove vacuum from component Apply vacuum to component
5. start Appropriate heading matching vehicle symptom is DOES NOT START Listed under DOES NOT START are more specific conditions Find specific condition which best describes vehicle malfunction Perform checks in order given DO NOT skip steps NOT pi Even if a diagnostic code is not set this article may refer you to a test procedure for a specific diagnostic code in the G TESTS W CODES TURBO article DOES NOT START Engine Does Not Crank Check starter Check starter relay Check park neutral or clutch start switch circuit Check theft deterrent ECU No Initial Combustion Check fuel pump circuit pM a DE SR A Check RPM sensor circuit Check camshaft position sensor circuit Check power stage circuit Check MAF sensor circuit Check ECT sensor circuit Check fuel pressur DIFFICULT TO START F HF a FF F HF FH FF F HF FF HF FH Difficult To Start Normally heck starter signal circuit heck Idle Air Control IAC valve circuit heck fuel pump control circuit heck ignition coil resistance heck distributor sensors heck spark plugs heck engine compression heck fuel injector circuit CO CECE CS CELENG Difficult To Start When Cold nsure battery is fully charged nsure spark plugs fire strong Blue White spark heck fuel pump fuse s heck in line fuse to control unit if applicable
6. sure spark plugs are not fouled heck ignition and sensor wires for proper connection heck idle valve Ensure airflow arrow points in correct irection heck distributor heck ignition and coil circuit heck intake system heck engine speed sensor or Hall Effect sensor turbo heck throttle switch and connector AAAAAQAAAQAKHQA Hesitation Poor Acceleration Defective airflow sensor Defective rotor distributor cap if applicable Damaged ignition wires Blocked air cleaner air intake Uneven compression Low fuel pressure Blocked exhaust system Faulty sensor signals Faulty turbocharger if applicable Wastegate valve open if applicable Hesitation Coasting Check fuel injectors Check ignition and sensor wires for proper connection Check throttle switch and connector Check engine speed sensor or Hall Effect sensor turbo Check for gasoline in oil Check idle valve Ensure airflow arrow points in correct direction Muffler Explosion Backfire nsure ignition timing is correct nsure timing belt has not jumped heck distributor heck for gasoline in oil nsure fuel injectors are not leaking nsure spark plugs fire strong Blue White spark heck ignition and coil circuit heck engine speed sensor heck throttle switch and connector heck exhaust system QAqgagagFnfnaAQAHE ts ngine Stall heck cold start injector if applicabl
7. tem Economy leaky fuel injectors rk plugs are not fouled faulty oxygen sensor ttle switch and connector turbo turbo poor wire connections and fouled spark plugs heck heck heck FH FH QAaAaAARAARAAAA Excess Check Check Check Check Check ngi for ive for for for ne speed sensor or Hall Effect sensor gasoline in oil for malfunctioning intake system HC amp NOx gasoline in oil leaky fuel injectors faulty oxygen sensor turbo ignition and sensor wires for proper connection Check Check FF HF FH ngi thro inta INTERMITTENTS INTERMITTENT PROBLEM DIAGNOSIS ne speed sensor ttle switch and connector ke system Intermittent fault testing requires duplicating circuit or component failure to identify the problem These procedures may lead to computer setting a fault code which may help in diagnosis monitor If problem vehicle does not produce fault codes voltage or resistance values using a DVOM whil le attempting to reproduce conditions causing intermittent fault A status change on DVOM indicates a fault has been located Use a DVOM to pinpoint faults When monitoring voltage ensure ignition switch is in ON position or engine is running is ignition switch in OFF position or negative battery cable is A Ensure disconnected when monitoring c
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