My craftsman 15.5 riding mower will crank, but not start when I turn on the ignition switch. I have traced all the electrical system, and everything gets 12 volts when it should. The solenoid works, starter turns, new spark plug fires. New battery, new ignition switch. Fuel line is clear and drains the tank well when disconnected from the carburetor with the fuel filter also still on the line. If the air filter is removed and the fuel is put into the top of the carburetor, the engine will start and run until this fuel is used up.

Seems to be related to the fuel shut off solenoid. An ohms check for continuity in the line from the "L" terminal of the ignition switch to the end of the hot line (not the grounded side) that connects to the fuel solenoid shows continuity. With this line disconnected from the fuel solenoid, a check across the two wires that go to the fuel solenoid (one grounded and one hot) shows 12 volts when the ignition is switched on. Also the engine fires and runs just fine if I just put a jumper in the end of this line while it is disconnected from the fuel solenoid. That grounds the line, bypassing the fuel solenoid.

Question: Since the engine will run with the fuel solenoid disconnected from electrical, why do I need it? Why do I need to replace it? What bad thing will happen if I just use the mower with it not connected to power? Also another odd thing: I get continuity with an ohm meter if I check across the two prongs of the fuel solenoid itself without the wires attached.

I've got a Craftsman 25HP POS and this solenoid is just designed incorrectly! It fills with gasoline and then the solenoid won't engage, it would need to compress the gasoline to do so.

I take it off and take it apart - it's only got a couple parts, and when the bottom is emptied, the solenoid can engage.

Now - the question is... can I just leave off the spring so it stays open all the time?

I wonder how important the fuel cut-off feature really is? I use to work on lots of motors in the past and they never had this thing, they shut off by grounding the eletrical system. It's probably required becase the newere motors run hotter and if the fuel is not shut-off they will probably diesel when you try to turn them off. I may have to try it.

Anyone know where to buy these things?

The fuel solenoid was designed for an anti backfire'you can bypass them but I would replaced it.
Luck

You my mower is doing this to it runs fine then after about 1 min of running it sputters and dies and then iot will work with the choke on full then it sputters and it won't run until you put gas in the carb then it will run on that gas only is that a bad carborator silinoid

I am the original poster of this thread. Since I asked this question, I have found the answer. Briggs and Stratton makes a carburetor identical to this carburetor, except it has no fuel shutoff solenoid. It works perfectly. The fuel solenoid is overkill to prevent flooding the engine, and too expensive to replace on a very old mower. I just unplugged the wire, left it hanging in a nonthreatening place, and installed the other carburetor. I got lucky and found a free used one that I cleaned up, otherwise cheapest I saw was $124. I suspect since the fuel shutoff solenoid is the only difference between the two (I compared the two closely), that you could just remove the shutoff solenoid and put a carburetor bowl bolt and gasket in its place and start mowing. Make sure the rubber tip on your carburetor needle (attached to the float) is in good shape and seals off good when the bowl is full, or you will have fuel flooding the engine and pouring out of the exhaust.

Another solution to this might be that if the solenoid is good, its needle might just need replacing if sticking, and then clean its seat. I just got rid of it.

After reading this, I went to replace my solenoid, but didn't want to pay the price of $63 for a new one! I took off the solenoid acouple of times and plugged it in to make sure it was working and it worked every time! Put it back into the carburetor and plugged it back in and it still worked! Could not understand why when I pulled the fuel line off, no gas, came out? Went to drain the tank and found out I had to take the cap off to do so! I decided the gas cap was either too tight or the vents on cap were plugged! So I cleaned the vented cap, and did not put it on so tight. Now it works fine! Try this before you buy a new solenoid!