Starts off good then eventually dies

[WinnerCougar74]

1974 Chrysler 135hp, has run good before, now it starts very well, idles very well for about 10 min, yesterday ran the engine up to about 3\4 throttle and it ran well for about 30 min then it seemed to miss a little for 5 min as we headed back to the dock, then it slowly died, started up with a lot of cranking then ran bad, tried to adjust idle needles, bottom carbs was weird, it ran faster and faster as I turn the screws into about 1\2 then died, top idle screw reacted normally, compression and spark is good on all cylinders, when I check the plugs they look fouled, I'm careful to use REC gas with 50-1 quicksilver oil,

My best guess is float levels or float seat not right or maybe resurculation circuit not working right and pooling of fuel flooding cylinders.

My fuel bulb is before my spin on filter. Is the a problem? Should it be after the filter?

 

[WinnerCougar74]

#4 plug - bottom


#3 plug - second from bottom

 

[WinnerCougar74]

#2 plug - 3rd from bottom

#1 plug - top

 

[foodfisher]

Check for fuel tank vent line plug. Sounds a bit like you are building up a vacuum.

 

[WinnerCougar74]

Found it. The fuel pump diaphragm was torn somehow. Is it possible to tear a fuel pump diaphragm by squeezing the fuel bulb to hard?

 

[Nordin]

I have not tear a diaphragm my self by squeezing the bulb, but if the diaphragm is old and brittle I think it is possible. Have you changed the diaphragm recently?
If you have, then maybe the diaphragm do not manage the ethanol in the fuel.
I am in Sweden Europe and we just have 5% Etanol in our fuel right now.
It might be more in the future.
I think in US the mixture of Ethanol is more then 5%.

 

[jerryjerry05]

One tiny backfire or cough can ruin the diaphragm.
Most likely the age is the problem??
Up to 10% Ethanol here

 

[WinnerCougar74]

The diaphragm is new. I use stay-bil this week because I can't get REC gas. Fuel is only a few days old. Fuel pump seems to be a week point on these motors.

 

[dingbat]

My fuel bulb is before my spin on filter. Is the a problem? Should it be after the filter?

Filters go on the vacuum side (in front of primer bulb) of the fuel system. Otherwise you pump the water that has accumulated in the filter back into the system.