Generac GT-990 — Testing Starter Motor Performance
Testing & diagnosis
For the Generac GT-990, from the Generac service manual.
Applies to: Generac GT-990 engine
Procedure
- A fully charged 12 volt battery is required.
- Connect jumper cables and clamp-on ammeter as shown.
- Activate the starter motor by jumping the terminal on the starter contactor to battery voltage.
- Note the reading on the clamp-on ammeter and on the tachometer (rpm).
- Take the reading after the ammeter and tachometer are stabilized, approximately 2-4 seconds.
Tools required
- clamp-on ammeter Amazon
- tachometer capable of reading up to 10,000 rpm Amazon
- fully charged 12 volt battery Amazon
- starter motor test bracket Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Minimum rpm 3250
- Maximum Amps 62
Source: Generac service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.