I think I need a gas check valve

[bigoledave]

Greetings,

My Colulumbia 29, 1965 has a nice aluminum fuel tank just below
the cockpit. I have an electric fuel pump, a spin on gas filter.

Whenever I disconnect my flex fuel line from my carn....then re install
iit after cleaning carb....I SOMETIMES need to suck or apply vacuum
to the line to start the fuel flowing to the filter....which is lower than
the gas tank bottom. I guess the problem happens because I shut
off the 90 valve on the tank exit line....then I disconnect the line to the
carb and I guess the residual fuel in the line drains out. So,,,,when
I connect it up and turn the tank on....there lledis no flow to the filter.as
the line in filled with air.

Sooooooo...I think I will buy an eight dollar check valve from Amazon
and mount it right at the carb inlet...
Comments appreciated..thanks

[Peter]

If you go this route make sure you use a metal check valve - plastic can melt/burn...

If I had this issue I would plug the fuel line while working on carb. I feel the fewer joints there are in the fuel line the more robust it will be.

My raving paranoia about spilled fuel hard at work.

Peter

[Sam]

Similiar set up in my 1966 Morgan - tank under cockpit, filter even with bottom of tank, electric fuel pump lower than filter but higher than carb [bulkhead mounts]. Because gas enters low side of pump and comes out high side when ever [and it is not often]I disconnect the carb fuel line gas only drains from that section of line - rest is still full resulting in no start up problem. Rather recommend 10 micron polishing filter and or fuel pressure gauge in front of carb inlet.

[Al Schober]

Check valve at the carb inlet? Why would gas try to be getting out of the carb?
Better might be at the outlet of the fuel tank or perhaps the inlet to the first fuel filter.

[bigoledave]

Ok.....I have had this boat since 1989...and never wanted a check valve before...sooo.fuugeddaboudit.

I had this recent "episode". I have a separate momentary switch in my cockpit which powers the electric fuel pump. Whenever I start the engine, I have
the large engine cover off ( easy on my boat) as I must access the 90 degree
valve at the fuel tank exit. Sooo..to start it up:

1) Remove cover
2) Turn on fuel
3) Reach up to cockpit and press the momentary switch.
4) ****Listen to the fuel pump...it SHOULD make a fast ticking sound
for a few seconds at most...then slows to a "tick" every few seconds.
If it does this, "all is well" as it indicates the fuel line entering the carb
is under pressure.
IF.....the pump just continues at a fast frequency...it ALWAYS means
there is no fuel entering the electric fuel pump.....which means either:
1) There is low or no fuel in the tank.
2) There is no fuel....just air...in the line coming down from the tank.
3) There is some obstruction in either the tank exit area or in the line.
****** Today when trying to start it up...the fuel puennmp just ran fast.
I disconnected the fuel line entering the fuel filter from the tank. This
connection is LOWER than the fuel tank, NO fuel dripped or flowed out.
Trying the simplest remedy first, I just disconnected the tank line at
the fuel filter and blew hard into the line. I then heard
loud bubbling in the fuel tank. As soon as I stopped, I lowered
the line to reconnect it...and fuel flowed out at high velocity. I quickly
re-attached it....then turned on the momentary switch. The pump
frequency slowed after ten seconds or so....and virtually stopped.
The engine started immediately. (YES..I do have a normal oil
pressure switch besides the momentary one.)

Conclusion....for some reason, there is possibly some type of loose
blockage in my tank...which I cleared by blowing in it. ?????????

[JOHN COOKSON]

Originally Posted by bigoledave

Conclusion....for some reason, there is possibly some type of loose
blockage in my tank...which I cleared by blowing in it. ?????????

Here's a possibility.
Crud in the tank at or near the bottom of the outlet hose is pulled up against the end of the hose while the pump is operating blocking the flow. When the pump is not operating (or you blow into the tube) the crud drops off.
If there is a filter on the end of outlet tube in the tank try removing it.
You can also try directing a hose to the lowest corner of the tank and pump out whatever might be causing the problem.
This sort of stuff can drive you nuts so.

ex TRUE GRIT

[Sam]

Well let's see - 1965 boat & you have owned since "89". If you haven't done so recently I would empty the tank and add fresh or at least filtered gas from the top 3/4's. Dump the bottom 1/4. A cheap sacrificial electric fuel pump mounted on a board connected to a battery to the battery and hose to the tank. I did this a couple of times few years ago on my 1966 when I was having irregular motoring problems. It cleaned up the tank fairly nicely but more importantly I was amazed of by the bottom "non-gas" and the gunk that came out. Due to local covid restrictions my boat sat in the yard an extra season so this year I emptied the tank again with a D cell battery stick transfer pump [found one with an extendable rod if your tank is deep from cockpit] and the bottom gallon was mostly water etc. Afterwards I filled the fuel lines to and from the bulk head mounted fuel pump using a turkey baster [good prime]. Engine started right up.

[joe_db]

Originally Posted by bigoledave

Conclusion....for some reason, there is possibly some type of loose
blockage in my tank...which I cleared by blowing in it. ?????????

I had that problem once and it drove me nuts. I found it by putting a vacuum gauge on the input side of the fuel filter. Vacuum on both gauges indicates a clog back at the tank, vacuum on just the output side of the filter is a clogged filter.
When I took the tank out I discovered the 1973 fill hose was dissolving and dropping rubber bits into the tank.