1957 7.5hp AD-11 starts but won't draw fuel…troubleshooting

[chri0891]

Not sure proper posting etiquette but I'm having a very similar issue to the person on this recent post (linked below) but that post didn't seem to get resolved. So rather than hijack that I thought I should start new.

I have great spark, newly rebuilt carb (float checked, ok), new impeller and seals, rebuilt (pressure) fuel tank with new fuel lines. Motor starts w/o fail w/ a bit of carb cleaner spray. Using the tank (~1/3 full, cap tight), the pushbutton fills the glass bowl and gets hard. After a couple pulls with choke out, motor tries to start. I push choke in 1/2way, next pull it starts (if I push choke in right away). It'll idle for 10-20 seconds, then dies. If I press the primer button on the tank every few seconds, it'll keep running. I've repeated this process dozens of times, enough that I've been able to adjust the slow speed screw - but since I can't get it running WOT in gear I haven't been able to properly set both throttles. High speed is out 3/4 turn and I notice small gas leak from that screw until it's running (despite replacing packing washers and tightening packing nut).

A couple things about the tank. Tank seems to hold pressure because I can pump gas into the motor and button gets hard when float cuts off flow (and cap will hiss if I loosen it at that point). But, when disconnected from the motor the connector sprays gas out the connector when button is pushed. Is that normal or should the spring hold the valve tight to the new o-ring?

My gut says the carb is ok but air leaving carb isn't making it to the tank, therefore not feeding fuel back to the motor? Is there a way to check for air problems at the carb and/or connector? Or a way to check the tank? Thank you-

-Brent

https://forums.iboats.com/forum/eng...inrude-outboards/10868236-fd-11-pressure-tank

 

[racerone]

The primer on the tank DOES NOT put pressure on the tank.------When motor starts , air is pumped into the tank to keep fuel flowing to the motor.-----The O-rings at the connecter must not leak.----The fuel filter in the glass bowl must be clean.

 

[F_R]

You said "My gut says the carb is ok but air leaving carb isn't making it to the tank, therefore not feeding fuel back to the motor? Is there a way to check for air problems at the carb and/or connector? Or a way to check the tank? Thank you-

You answered your own question when you said the air hisses out when you loosen the cap. But you also say it keeps running if you pump the button. So we are missing something here.

 

[chri0891]

I repeated the process today and tried to be a little more scientific in the approach:

1) I hooked compressor up to the air line (from the fuel connector) and injected a very light shot of air into the tank. I could hear a slight leak at the tank (more on that later), but after a few seconds, fuel started to drip out of the connector.
2) I disconnected the fuel line at the connector and plugged that end with a screwdriver. Again, tiny bit of air injected into the air line. I sprayed soapy water on the tank. No leaks around the edges or screws or cap but I DID have air leak around the glass bubble over the E-1/2-F gage. I find that put under pressure it sits up a 1/4" or so. I can push it down and it relieves the pressure in the tank; let go and it pops back up and builds up pressure again. Is this some sort of built-in venting system to avoid too much pressure build-up in the tank? Or should there be a seal there holding that glass bubble firm?
3) With the connector now off, I wrapped the finger of a latex glove around its stem like a balloon and shot some air into the valve (motor side). It inflates (no obstructions) and then deflates from the size of a golf ball to nothing in about 5-6 seconds (o-ring seal isnt perfect around the valve stem).
4) I hooked up the connector back to the motor (with fuel line ONLY, keeping the balloon on the air side). Primed the gas tank to firm, choke out, motor started for a second on the first pull, put choke in, motor started and idled on the next pull. Sure enough the balloon inflates to golf ball size within a couple seconds - so air is making it through the connector.

I'm still somewhat stumped (unless that glass bubble on the tank is not supposed to act like a pressure relief valve). Only other source I could think of is that round rubber gasket that goes above the glass bowl at the filter. BTW racerone, the fuel filter is brand new off ebay (mine had lots of rust on it). But I didn't replace the gasket, I thought I could use an o-ring but tried it and didn't like how the glass bowl wanted to slide around on the round profile, so I threw the original (flat) gasket back on. That said, you'd think if it was leaking there would be gas on the motor cover, and there is not.