BillM Posted January 28, 2025 Report Share Posted January 28, 2025 When I turn on the ignition there is a short blip of power to the fuel pump down on the frame. Shouldn't there be constant power when the ignition is on? Bill Quote Link to comment
BillM Posted January 28, 2025 Author Report Share Posted January 28, 2025 Found my own answer- power comes on full time when the engine is started/running. Bill Quote Link to comment
datzenmike Posted January 28, 2025 Report Share Posted January 28, 2025 Can only be whatever the battery is. If going by the sound of the pump it will race slightly till pressure builds and it has to start working against the resistance. Quote Link to comment
BillM Posted January 31, 2025 Author Report Share Posted January 31, 2025 I lied, it has a carb Bill Quote Link to comment
datzenmike Posted January 31, 2025 Report Share Posted January 31, 2025 Fuel pump s a fuel pump. EFI ones are about 10X more pressure. 720 EFI engines have two wing nuts holding the air filter on. They also have an "Electro Injection' sticker on the air filter. Quote Link to comment
powderfinger Posted January 31, 2025 Report Share Posted January 31, 2025 If you actually have a carb then you should always hear the fuel pump. At least everyone I have ever owned ran all the time. If you have a throttle body the fuel pump will shut off after some time if the ECU doesn't get a signal from the crank angle sensor. Pretty sure that's how it works, haven't looked in quite sometime after converting mine from throttle body to carb. Quote Link to comment
datzenmike Posted January 31, 2025 Report Share Posted January 31, 2025 On 1/28/2025 at 2:50 PM, BillM said: When I turn on the ignition there is a short blip of power to the fuel pump down on the frame. Shouldn't there be constant power when the ignition is on? Bill No. There is a timer on the fuel pump relay. It comes on with the ignition for a length of time, but if you don't try to start, it shuts off when it times out. When starting even low oil pressure will keep the pump operating. If on the other hand the engine starts, a charging alternator OR oil pressure will keep the fuel pump operating. You don't actually need the fuel pump to start your 720. There is more than enough fuel in the carburetor, from the last time it was running, to start the engine and drive down the block. Once the engine starts a charging alternator or oil pressure will keep the engine running. If wondering if you are getting fuel to the carburetor just look on the front of the carburetor body. There is a sight glass where you can see the fuel inside. Quote Link to comment
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