How purge the fuel system?

This was a PM sent to me and I thought it worthy of sharing.


txpower_ram wrote:I need to replace the fuel filter on my little jap truck. How important is to purge the fuel system? Why cant I just disconnect hoses, put a shop rag over the line to stop any gas and change out the filter. Like on my tractor? I feel nervous messing with relays,computers, and such.

You don't have to mess with any of that to purge the line. You can simple find the fuel rail on the engine and purge it with the engine off. All you are doing is relieving the pressure in the line. Fuel pressure runs at 35 to 45 psi. Enough to cause air bubbles to be forced through the skin and into the blood stream which causes certain death. Same reason they tell you not to use an air hose from an air compressor to dry water off your hands or any part of your body. A drive in car wash has enough pressure to do the same thing as well, so you don't want to point that at any one either.

Look for a schrader valve on the fuel line around the engine. Looks like a tire valve stem. Take a small screw driver and press the plunger down and let the pressure escape. Then swap the filters out. Less mess that way and more safe too. Put a shop towel over it too and don't push it all the way in, just enough to get it to start relieving the pressure.