old style, new style gas tank diaphragm question

[huntleybill]

I am restoring an Evinrude Cruise a day 6 gal fuel tank. I have replaced the o-rings in the connector, replaced the dual fuel line, replaced the gasket on the tank itself, and put in a new diaphragm. The original diaphragm had a hole for the plunger, the new one did not so I punched a hole in it. When I pump it up, I get no pressure build up. I removed the mechanism several time to make sure everything is in correctly. Best I can tell, everything is in correctly.

What I was wondering is, are the diaphragms with the hole in them different than the one without a hole? Are they interchangeable or not?
Or, could there be another reason why a tank would not develop pressure?

[olcah]

Suggest checking to see that the new oring in the connector is seated. I have seen it written that the hole is the only difference in the gaskets.

[Mumbles]

Make sure the check valve at the bottom of the pickup tube is free and operational. This can be done by giving it the suck and blow test while it is off. If the check valve is stuck, the primer pump won’t be able to draw any fuel up out of the tank.

[David Bartlett]

When you say it doesn’t pressurize, are you saying it won’t pump fuel through the hose? The primer on the tank does NOT pressurize the tank. The running motor does that.

David Bartlett
Pine Tree Boating Club Chapter

"I don't fully understand everything I know!"

[ede]

Tank will not pressurize with the primer plunger. That is a fuel pump to transfer fuel from big tank to carb.

[wedgie]

Check that the fill hole cap is sealing. 301835 gasket could be bad or missing

[labrador-guy]

Mumbles has the answer for you! That check valve in the pickup is probably stuck. It is right on the end of the pickup tube by the screen filter.

dale

[huntleybill]

Thanks guys. Let me clear up some of your questions.

When I say it won’t pump up, I mean that it will lot pump fuel to the carb when pumping the plunger. (although I do have my pressurized “test Tank” that does “pressurize” the tank. I know this because it pumps up and I can then loosen the cap and it hisses to equalize pressure.

I have checked the check valve by taking it off and sucking and blowing into the tube. I have also replaced the check valve with a known good tank and got the same result.

I have checked the gasket in the cap and it is not dry rotted, rock hard, or missing. I “think” it is ok.

Also, I have attached the tank to a motor (in order to see if the connector is leaking) and I could not get it to pump fuel to the carb. (no fuel fills the glass bowl).

This is why I was asking if the diaphragm is different for the new versus old tanks.

• This reply was modified 4 years, 3 months ago by huntleybill.

[David Bartlett]

Do you by chance have the connector on “backwards”? I did that once with the fuel hose connected to the “Air” side of the connector. Same thing you are describing.

David Bartlett
Pine Tree Boating Club Chapter

"I don't fully understand everything I know!"

[huntleybill]

Thanks David. I was very careful when i put the connector on to get it right but when you mentioned it, I wasn’t sure. So, I went out and double checked. The connector is on correctly. However I tried pumping it again for a minute or so and could not get it to pump up. So I then pushed in on the fuel side of the connector with a small screw driver to open the passage. The tank then pumped up and squirted about 6 feet across the room! The connector was NOT bound up but even if it was, I don’t see why it wouldn’t pump up??

I’m confused but I guess I shouldn’t look a gift horse in the mouth!
Take the win and run with it!

Thank you all for the help.

[Author]

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