OMC Dual Line Fuel Tank Pick-up tube

[Buccaneer]

Is there a check valve in the pick-up tube in the subject tank?
I’m fixing up a tank, and it had a lot of crud, scale, and goo in
it, including the pick-up tube.
I was able to remove the foot (with screen) from the tube.
There looks like there’s a disc inside the foot assembly,
but I can’t get it to rattle. I finally got some flow thru the foot
if I "suck", very little if I "blow".
I soaked it overnight in solvent, then "boiled" some WD40 in
it with a bottle torch and got a lot of crud out.
Still wondering if it’s partially crudded up, if there’s a check valve inside,
and if so, should it rattle?
Thanks!

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Attachments:

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[garry-in-michigan]

Yes – that disk is a check valve and should rattle when shaken. . . 😎

[Buccaneer]

I took the suction foot assembly apart via rod, pliers, and hammer.
Came apart easier than anticipated, and of course, whatever
was inside for a check valve disc went flying, never to be seen again.
I turned a tin aluminum disc on the lathe, and loosely assembled
everything. Disc works great to keep air flow (gas) in the correct direction,
but sometimes, if I suck hard enough, also blocks flow from the
"running" direction. Wish I knew what the original looked like,
or better yet, "find it!"
I thought I had the screen pretty clean from soaking and wire brushing,
but when I "popped" it out, I could hardly see light thru it, so made
a new one. Also plenty of crud remained in the check valve housing,
even after all that boiling out with WD40.
Thanks.

Prepare to be boarded!

[garry-in-michigan]

They originally used a stainless steel ball which always centered itself, but it seemed to get stuck down a lot. The disk was an improvement. The tank pump hopefully shouldn’t develop enough negative pressure to give you trouble. If it does, use stainless steel for the next one . . . 😎

[chris-p]

Probably MUCH easier to salvage one from a rusty tank.

[Buccaneer]

I didn’t get back to play around with the check valve anymore today.
Tomorrow I’ll play around with it. I was thinking about putting a
very light spring above the check valve disc so it couldn’t close
all the way and shut off gas flow. If the tank is only operating under 2-3 psi
to push the gas out of the tank, my spring would need to be pretty weak
I’m guessing. I’m sure some engineer used "math" to figure it all out.
I’ll have to "guess"!
I may have a pickup tube from a rust single line tank, but they look completely
different in the diagrams.

Prepare to be boarded!

[garry-in-michigan]

A single line tank doesn’t have any valves. The valves are in the primer bulb in it’s fuel line. . . 😎

[Buccaneer]

quote Garry in Tampa:

A single line tank doesn’t have any valves. The valves are in the primer bulb in it’s fuel line. . . 😎

That would make sense Garry!

I didn’t think about it until I had my dual line guts all back together,
but does the primer button pressurize the tank to move fuel,
or suck it up the pickup tube?

I got the homemade check valve disc to work good now. I must be smarter in
the morning. 😕 I realized the pickup tube protrudes into the check valve
body slightly, and the tube has a notched end, that keeps the disc from
opening too far, yet allows fuel to get into the tube.

I thought I had the original pickup screen pretty clean with wire brushing and
solvent, but decided to take the old screen out, and I was aghast at the amount
of crud in, and behind the screen. Decided to make a new screen!

Also, tore apart a rusty / crusty tank assembly from an OMC single line tank
to measure the O-rings. The two little valves behind the core plugs have
a tapered seat, and the o-rings I removed had a tapered ID.
Whether the taper in the o-ring was manufactured or just took that shape
from years of spring pressure on the tapered valve, I don’t know.
Anyone know for sure?
The closest I could measure these o-rings are…..
OD- .325
ID- .170
CS- .075 (cross section / wall thickness)
The closest I see in an O-ring size chart is OD- 5/16" x ID 3/16" x CS 1/16".

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Attachments:

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[david-bartlett]

Buc,

The primer does not pressurize the tank, just moves fuel to the motor to start it.

[fisherman6]

The primer button functions as a liquid pump by drawing fuel up the pickup tube and pushing it to the carburetor. The crankcase pressure from the engine is the only thing that pressurizes the tank. 😉
-Ben

OldJohnnyRude on YouTube

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