OM606- Sanity check fuel line air leaks
OM606- Sanity check fuel line air leaks
I think you might be right but then I guess I don't understand how it can function without some type of one way valve? In my mind, the main spin on filter, well...the entire supply side of the system really, is on the "suction" side of the pump. If there is a passage from the spin on filter (fuel supply- suction- side) to the return line (which does have air in it), than under suction it would be more likely to suck in air from the return line than expel air to it... being that the supply side is at a lower pressure than the return side... no?
In one of my many attempts to purge the system of air after a no start, I disconnected the rubber return line from the plastic tee where it ties into the filter housing. I put about 5 PSI of pressure in the return line (and as a result into the tank) to force fuel through the supply side of the system in the hopes that it would purge all the air and fill the filter and all the plastic lines. I disconnected the last supply line that feeds the injection pump. It didn't work. I was getting fuel under pressure out of the return line TEE where the rubber hose normally goes so I suspect your correct that there is a connection between the supply and return sides of the fuel system at the filter housing. the filters and lines never filled with fuel. I'm pretty sure you can't force fuel through the lift pump and/or SOV this way so the filters won't accept the pressurized fuel due to the back pressure from either the lift pump or the SOV. I tried both with the SOV energized and de-energized so I suspect it's the lift pump that resists flow.
Also- I bypassed the pre filter completely. I read on another site the line that goes from the pre-filter base to SOV CAN be removed from the pre-filter base and connected directly to the fuel heat exchanger if you just rotate the fitting about 20 degrees. That did work and it looked like a good seal. The next day, that line was full of air. I'm not sure if I had retightened the return line at the TEE and think perhaps the air came in through there??
My next attempt is I'm adding a fuel check valve in the supply line near the tank. I hope this works as I really don't want to add an electric lift pump.
Thanks Alec-
I think you might be right but then I guess I don't understand how it can function without some type of one way valve? In my mind, the main spin on filter, well...the entire supply side of the system really, is on the "suction" side of the pump. If there is a passage from the spin on filter (fuel supply- suction- side) to the return line (which does have air in it), than under suction it would be more likely to suck in air from the return line than expel air to it... being that the supply side is at a lower pressure than the return side... no?
In one of my many attempts to purge the system of air after a no start, I disconnected the rubber return line from the plastic tee where it ties into the filter housing. I put about 5 PSI of pressure in the return line (and as a result into the tank) to force fuel through the supply side of the system in the hopes that it would purge all the air and fill the filter and all the plastic lines. I disconnected the last supply line that feeds the injection pump. It didn't work. I was getting fuel under pressure out of the return line TEE where the rubber hose normally goes so I suspect your correct that there is a connection between the supply and return sides of the fuel system at the filter housing. the filters and lines never filled with fuel. I'm pretty sure you can't force fuel through the lift pump and/or SOV this way so the filters won't accept the pressurized fuel due to the back pressure from either the lift pump or the SOV. I tried both with the SOV energized and de-energized so I suspect it's the lift pump that resists flow.
Also- I bypassed the pre filter completely. I read on another site the line that goes from the pre-filter base to SOV CAN be removed from the pre-filter base and connected directly to the fuel heat exchanger if you just rotate the fitting about 20 degrees. That did work and it looked like a good seal. The next day, that line was full of air. I'm not sure if I had retightened the return line at the TEE and think perhaps the air came in through there??
My next attempt is I'm adding a fuel check valve in the supply line near the tank. I hope this works as I really don't want to add an electric lift pump.
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