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 MANUALSCHEVROLET1990LUMINA APV V6-191 3.1LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONINITIAL INSPECTION AND DIAGNOSTIC OVERVIEWCHECKING THE BASICS
1990 Chevrolet Lumina APV V6-191 3.1L
Checking the Basics
1990 Chevrolet Lumina APV V6-191 3.1LSECTION Checking the Basics
This section is used to find the correct test procedure for a given symptom. The symptoms and actions in this section are FUEL RELATED ONLY. Always use the FLOW OF DIAGNOSIS for proper testing sequence. Verify the correct system application to ensure that the vehicle has the given component. Verify that the problem is not in the ignition system.
ALCOHOL-IN-FUEL
Alcohol-in-fuel can be detrimental to fuel system components and may cause driveability problems such as hesitation, lack of power, stall, no start, etc.
The problems may be due to fuel system corrosion and subsequent fuel filter plugging, deterioration of rubber components and/or air/fuel mixture leaning.
Various types and concentrations of alcohols are used in commercial fuel. Some alcohols are more detrimental to fuel system components than others. If an excessive amount of alcohol in the fuel system is suspected as the cause of a driveability condition, refer to ALCOHOL-IN-FUEL TEST. In this procedure water is used to extract the alcohol from the fuel.
FUEL TYPES
Methyl Tertiary-Butyl Ether: (MTBE)
Fuel containing Methyl Tertiary-butyl Ether (MTBE) may be used, providing there is no more than 15% alcohol by volume.
Ethanol:
Fuel containing ethanol (ethyl) or grain alcohol may be used, providing there is no more than 10% ethanol alcohol by volume.
Methanol:
Fuel containing methanol (methyl) or wood alcohol may be used, providing there is no more than 5% methanol by volume. Use of fuel (gasohol) that contains more than 5% methanol can corrode metal fuel system components and damage plastic and rubber parts.
PRE-CHECKS:
1. Check for adequate fuel supply in fuel tank. DO NOT RELY ON FUEL GAUGE!
2. Verify battery is fully charged.
3. Verify fuse/fuse link integrity.
4. Inspect all hoses, fuel lines, and connections for fuel leaks, kinks and proper routing.
5. Verify correct fuel type and quality.
6. Check TSB's for fuel system design updates.
ALCOHOL-IN-FUEL
Alcohol-in-fuel can be detrimental to fuel system components and may cause driveability problems such as hesitation, lack of power, stall, no start, etc.
The problems may be due to fuel system corrosion and subsequent fuel filter plugging, deterioration of rubber components and/or air/fuel mixture leaning.
Various types and concentrations of alcohols are used in commercial fuel. Some alcohols are more detrimental to fuel system components than others. If an excessive amount of alcohol in the fuel system is suspected as the cause of a driveability condition, refer to ALCOHOL-IN-FUEL TEST. In this procedure water is used to extract the alcohol from the fuel.
FUEL TYPES
Methyl Tertiary-Butyl Ether: (MTBE)
Fuel containing Methyl Tertiary-butyl Ether (MTBE) may be used, providing there is no more than 15% alcohol by volume.
Ethanol:
Fuel containing ethanol (ethyl) or grain alcohol may be used, providing there is no more than 10% ethanol alcohol by volume.
Methanol:
Fuel containing methanol (methyl) or wood alcohol may be used, providing there is no more than 5% methanol by volume. Use of fuel (gasohol) that contains more than 5% methanol can corrode metal fuel system components and damage plastic and rubber parts.
PRE-CHECKS:
1. Check for adequate fuel supply in fuel tank. DO NOT RELY ON FUEL GAUGE!
2. Verify battery is fully charged.
3. Verify fuse/fuse link integrity.
4. Inspect all hoses, fuel lines, and connections for fuel leaks, kinks and proper routing.
5. Verify correct fuel type and quality.
6. Check TSB's for fuel system design updates.
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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.