Why generators show "engine will not crank": 32 documented causes and brand-specific fixes, compiled across 12 manufacturers.
NO VOLTAGE MEASURED 12 VDC MEASURED
2 brands- GP Series: RECHARGE OR REPLACE BATTERY – CLEAN, REPAIR OR REPLACE BAD CABLE(S) BAD REPLACE BAD GOOD NO VOLTAGE MEASURED BAD 12 VDC MEASURED REPLACE STARTER MOTOR IF DEFECTIVE GOOD CHECK FOR MECHANICAL BINDING OF THE ENGINE OR ROTOR
- Generac: RECHARGE OR REPLACE BATTERY – CLEAN, REPAIR OR REPLACE BAD CABLE(S) BAD REPLACE BAD GOOD NO VOLTAGE MEASURED BAD 12 VDC MEASURED REPLACE STARTER MOTOR IF DEFECTIVE GOOD CHECK FOR MECHANICAL BINDING OF THE ENGINE OR ROTOR
Low battery output voltage or discharged battery.
2 brands- Generac: Charge or replace batteries. See Battery Installation and Replacement. Loose or corroded connections. Clean and tighten connections. Replace as necessary. Faulty start circuit relay. Contact a GMP ASD.
- Isuzu: Charge or replace batteries. See Battery Inspection. Loose or corroded connections. Clean and tighten connections. Faulty start circuit relay. Contact a GMASD.
Indicates possible fault with control or starting system. Check for the following conditions: a. Fault lamp on. Correct fault and reset control. b. Poor battery cable connections. Clean the battery cable terminals and tighten all connections. c. Discharged or defective battery. Recharge or replace the battery. d. Emergency stop button (if equipped) pushed in. To reset, pull switch out and move Run/Stop/Remote switch to Stop position. Then push test switch to Reset/Lamp position. e. Contact an authorized service center if none of the above.
2 brands15 ampere fuse element has melted open
1 brand- Generac: Push in on fuse holder cap, rotate cap counterclockwise, then remove cap and fuse. If the fuse element has melted, install an identical 15 ampere fuse
PTO drive is engaged, Battery (if equipped) is discharged, Safety interlock switch is engaged, Loose or faulty wires or connections, Faulty key switch or ignition switch, Faulty electric starter (if equipped), Retractable starter not engaging in drive cup, Seized internal engine components
1 brandBlown fuse.
1 brand- Generac: Correct short circuit condition by replacing 7.5 A fuse in generator control panel. Contact an IASD if fuse continues to blow.; Correct short circuit condition by replacing 7.5 A fuse in generator control panel. Contact an Independent Authorized Service Dealer (IASD) if fuse continues to blow.
1. Battery weak or dead.
1 brand- Generac: 1. Recharge or replace battery (see 'No Battery Charger DC output' at bottom of guide). 2. Start engine manually using recoil starter.
A. Faulty safety interlocks. b. Discharged or defective battery. c. Faulty electrical connections. d. Faulty starter motor switch (open circuit). e. Open circuit in starter motor. f. Brushes sticking, etc. g. Faulty solenoid.
1 brandPTO drive is engaged. Battery (if equipped) is discharged. Safety interlock switch is engaged. Loose or faulty wires or connections. Faulty key switch or ignition switch. Faulty electric starter (if equipped). Retractable starter not engaging in drive cup. Seized internal engine components.
1 brandPTO drive is engaged. Battery is discharged. Safety interlock switch is engaged. Loose or faulty wires or connections. Faulty key switch or ignition switch. Faulty electric starter or solenoid. Seized internal engine components.
1 brand- Battery discharged or faulty - Battery charger (aux. AC powered) malfunctioned - Corroded battery terminals - Faulty starter motor - Faulty starter solenoid - Faulty start relay - Engine in seized condition
1 brandBlown fuse
1 brand- Generac: 1. Correct short circuit condition by replacing 7.5 amp fuse in generator control panel. Contact an Independent Authorized Service Dealer (IASD) if fuse continues to blow. 2. Tighten, clean, or replace as necessary.* 3. *See #2. 4. *See #2. 5. Charge or replace battery.
Loose, corroded, or defective battery cables
1 brand- Generac: 1. Correct short circuit condition by replacing 7.5 amp fuse in generator control panel. Contact an Independent Authorized Service Dealer (IASD) if fuse continues to blow. 2. Tighten, clean, or replace as necessary.* 3. *See #2. 4. *See #2. 5. Charge or replace battery.
Defective starter contact
1 brand- Generac: 1. Correct short circuit condition by replacing 7.5 amp fuse in generator control panel. Contact an Independent Authorized Service Dealer (IASD) if fuse continues to blow. 2. Tighten, clean, or replace as necessary.* 3. *See #2. 4. *See #2. 5. Charge or replace battery.
Defective starter motor
1 brand- Generac: 1. Correct short circuit condition by replacing 7.5 amp fuse in generator control panel. Contact an Independent Authorized Service Dealer (IASD) if fuse continues to blow. 2. Tighten, clean, or replace as necessary.* 3. *See #2. 4. *See #2. 5. Charge or replace battery.
Common questions
What causes engine will not crank?
Common causes, most-reported first: NO VOLTAGE MEASURED 12 VDC MEASURED; Low battery output voltage or discharged battery.; Indicates possible fault with control or starting system. Check for the following conditions: a. Fault lamp on. Correct fault and reset control. b. Poor battery cable connections. Clean the battery cable terminals and tighten all connections. c. Discharged or defective battery. Recharge or replace the battery. d. Emergency stop button (if equipped) pushed in. To reset, pull switch out and move Run/Stop/Remote switch to Stop position. Then push test switch to Reset/Lamp position. e. Contact an authorized service center if none of the above.; 15 ampere fuse element has melted open; PTO drive is engaged, Battery (if equipped) is discharged, Safety interlock switch is engaged, Loose or faulty wires or connections, Faulty key switch or ignition switch, Faulty electric starter (if equipped), Retractable starter not engaging in drive cup, Seized internal engine components; Blown fuse..