Fuel pressure
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Cruiser
Joined: Sep 2013
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From: florida
Fuel pressure
Hello All; Probably a dumb question but when i get home from a ride i always top off my gas tank so i'm full for the next ride. so of course the pressure in the tank is gone till the next time i ride. Does it matter one way or the other if theres pressure in the tank/lines while sitting?
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Joined: Apr 2010
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From: Western MD
totally normal for fuel injection to hold pressure between pump and injectors for a certain amount of time. over the course of a few hrs it should bleed down to very little pressure. if it drops off quickly theres a problem. as long as theres enough fuel in the tank to cover the fuel pump pickup and there are no leaks, the pressure readings will be the same regardless of how much fuel is in the tank.. 1/8 to full it will be the same pressures.
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From: Rolla
Hello All; Probably a dumb question but when i get home from a ride i always top off my gas tank so i'm full for the next ride.
so of course the pressure in the tank is gone till the next time i ride. Does it matter one way or the other if theres pressure in the tank/lines while sitting?
so of course the pressure in the tank is gone till the next time i ride. Does it matter one way or the other if theres pressure in the tank/lines while sitting?
As you know, the fuel pump is inside the fuel tank. The pressure is from the fuel pump (outlet side) to the injectors.
The inlet side of the pump (fuel in your tank) isn't pressurized.
And as mentioned, once you shut the engine down it will slowly bleed that outlet pressure off.
To prove your tank isn't pressurized, you can remove the fuel cap with the engine running and nothing will happen.
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From: Honah Lee
Your tank is vented by a hose at the top front just in front of your speedometer. The hose looks like an electrical line coming down at the fork triple tree neck and is routed back and down in front of the rear tire. The fuel cap is not vented. On a car, the hiss you hear is not pressure but a vacuum. There are three lines on most new cars. A pressure fuel line going to the engine fuel rail that the injectors set in and a return since the fuel pump runs all the time the engine is running maintaining about 60 lbs pressure and bleeding off excess back to the tank. The third line is a vacuum to the charcoal canaster that purges to the intake. On a car, that is why it will throw a code if you leave the gas cap loose. Your Harley will maintain injector pressure for a short period but on key on, the fuel pump runs for 3 seconds from a timer in the system relay. Once the engine starts, it fuel pump runs all the time or as soon as the ECM reads the engine is turning. If the bike is dropped, there is a kill switch called a bank angle switch in the signal light and or alarm that turn the fuel pump off. You can see my vent hose in the lower left just above left shock. CA bikes and maybe even new ones have canisters on the end. The bank angle switch and my alarm is what the large white plug is hooked to. Just below it you see another unused plug for the optional alarm siren. The upper red and yellow connectors is the charging circuit breaker.
Last edited by Jackie Paper; Nov 27, 2013 at 07:05 PM.
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