I have a 500 amp battery jump-starter # j5c09ca i know i have to charge it for 40 hrs before first use. after that do i have to charge it for 40 hrs.each time

The flashing "FL" indicates that the internal battery of the Peak Performance Jump Starter # PKC0AZ is fully charged and is ready to be used.

then buy a new starter

Not sure what the question is. These units have a sealed gel cell battery that can be replaced (Have done that) and they do fail after several years. Is yours charged? https://www.stanleytools.com/products/automotive-tools/other-tools/power-station/500-instant-1000-peak-amp-jump-starter-with-compressor/j5c09 BE sure last connection when jumping is negative and body to body - away from battery

http://media.wix.com/ugd/217982_8aaa2b786e2a4579baf84c342011767f.pdf

The only difference between this model, and the j7csr is this:

• Bonus Priority Auto Assistance road-side service

Roadside Assistance program information and activation are included with the Jumpstarter. Whenever you travel, you'll like the secure and confident feeling of knowing that you are protected by Priority Auto Assistance.
12 Month Membership Includes:
24 hrs Emergency Roadside Assistance, 24 hrs Towing Service, 24 hrs Mechanical First Aid, 24 hrs Tire Change Service, 24 hrs Emergency Delivery, 24 hrs Emergency Battery Service, 24 hrs Lost Key Service, Rental Car Discounts, Map Routing Service and Theft/Hit & Run Protection Services

Depends how long the unit has been just 'sitting' without being used! My neighbour had a similar problem after leaving his for over a year unused. The battery that's in it simply died. In order to maintain these units in good working order they need to be used regularly - that is charged and discharged. The unit may need a new battery I'm afraid!

The starter has to throw it's gear out using centrifugal force. The speed of the starter has to be enough to overcome the spring inside. It is either a little seized and needs to be rebuilt and greased up, or the battery isn't powered up enough to get the right speed to engage properly. In that case clean the battery posts and clamps well, then charge or replace the battery. To know if the battery is bad wait till it is charged... if it still doesn't engage try again with booster cables from your car etc. and see if it suddenly works fine.

If the battery is real low, It takes about 8 hours to recharge it,

I can't find any reference to a Homelite model 720 generator but most battery charging systems do not supply enough amps to run a car starter. Battery chargers usually work in the two (trickle) to ten amp range. Car starters need way more amps to have enough power to turn an engine over, depending on the size and number of cylinders in the motor. Some chargers have a switch with a 60 amp 'start' position to help the battery turn the motor over, but without that there is little chance the charger side of your generator will supply enough amps to help your battery.

Could be one of two things.

1. Your starter motor is no good.
2. If you turn on your lights and try to start the car and they dim to almost black, then you need to check the battery connections.