D17 Series 3 Gas, fuel concern

I replaced my gas cap with a new one and now with the cap tight it vapor locks. When I open the gas cap I can hear the air go into the tank. This maybe your problem too, mine will stop and I have to take the cap off for it to restart again. Hope this helps you.

I would second the stuck needle in the carb. If the tank was vapor locking I wouldn't think cracking the line at the carb would fill the inline filter. I would also wonder if the inline filter is big enough for a gravity feed system. You can get them with enough flow. I ran my d17 serries 1 that way for years but the inline filter has to be for gravity feed.

Open the main jet on the carb 2 full turns and try it. If the problem remains the same, remove the plug from the bottom of the carb bowl and with a funnel, catch the gas running out of the carb drain plug hole. IT HAS TO BE ABLE TO FILL A 5 GALLON PAIL IN ONE HOUR OR LESS. If the fuel flow doesn't meet this 5 gall per hr (or more) rate, you have a fuel flow problem somewhere. Then, determine if it's the carb or fuel line/sediment bowl with the same type of testing.

Most easily found inline filters are for pressurized systems which isn't gravity flow. In a gravity flow system they will restrict fuel flow.

There are several possible causes of poor fuel flow. Modern gas caps won't vent, though venting caps are made. Most tractors depend on the gas cap for the vent. Usually if there's a lack of venting in the cap, the engine will run fine for 10 or 15 minutes then run lean and stall.

The main jet adjustment has to be made with the engine running, not just to the book setting. The book setting is just good enough so the engine will run to allow proper setting for maximum speed with the throttle held fixed (else the governor will hide the effects of mixture adjustment).

Many tractor carburetors have a screen on the inside of the carburetor inlet fitting. I've see that clogged to the point the engine would only idle for a minute every 15 minutes. When pulled it wouldn't pass air from my portable air tank at 65 psi.

Floats can get bent and drag on the side of the float bowl. Needles can stick to the seat, but both of these problems usually mean they don't shut off, but they can stick nearly closed. Passages in the carburetor like the lines to the jets and the air vent can get plugged with varnish and grunge and restrict fuel getting to the engine.

Air leaks between the venturi area of the carburetor and the intake valves, like the shaft seal of the throttle valve, the gasket from carburetor to intake manifold, and the gasket from intake manifold to head or block can rot, and occasionally an intake manifold can rust through killing intake vacuum, then the carburetor won't work well. And on some engines there is a little valve on the intake manifold either used for cold weather priming or for supplying vacuum to a cow milking machine.

Ignition power and timing also has a big effect on engine running.

Gerald J.