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Are duel fuel check valves necessary?

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fishnfowlr

New member
First off, I have a 1994 Mercury 225/3/0L. Recently I've experienced low fuel pressure to the point of having to pump the hand bulb to get the motor running up to full speed. I rebuilt the fuel pump (but all the diaphrams, ect. looked good from what I replaced). I replaced all the fuel lines from the tank to the carb. I pulled all three carbs and cleaned all jets and inspected the float, needle and seat for proper operation. I replaced the fuel/water separator. Today, while Isaac rained on my parade, I decided to dig a little further. Thinking the hand pump check valve may have been faulty in the new pump, I replaced it again and went to a larger, 3/8 fuel line. Still, I couldn't get good fuel flow. I pulled the stem from the bottom of the valve from the fuel tank. The filter in the bottom of the stem is clean. I unscrewed the valve off the top and it has a spring loaded check valve where the main fuel line hooks to the tank. Is this check valve necessary? I took carb cleaner and did my best to clean it. It still takes a certain amount of pressure to pull fuel from the tank. I'm thinking that this extra pressure is what's keeping my motor from running properly. I have a check valve in the hand pump. Do I have to also have another check valve coming from the top of the tank? One thing I have not checked but have heard about is the reed vavle. Not sure where it's located but I do have the specs on the opening of each reed. Any help would be greatly appreciated. Brad
 
kimcrwbr1 said:
You did leave the cap off the fuel tank. if the vent is restricted you will get the same condition if the tank goes into a negative pressure or a vacuum.
Click to expand...

the vent does not appear to be restricted. When I fuel the tank, I can feel a good flow of air coming out the side vent and fuel will spill out if i continue to overfill. Still, my main question is not answered. Is there a major reason why there is a spring loaded check valve/ball coming directly from the tank? It probably takes a couple pounds of pressure to activate/push the spring/ball and allow fuel to flow out of the tank. I think I'll bypass that and use a non-check valve assembly that does not require pressure to allow fuel to flow from the tank. The fuel is fairly new and I keep stabilizer in the fuel. I only use premium and have gone through several tanks this summer. Thanks for the acetone suggestion. I'll keep that as plan b.
 
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