Thanks Bill and Mownie for the tip to replace trouble solenoid. Today I put in new solenoid, engine start right away, Gas idle at high and low RPM are very smooth. I released the brake and shift into forward gear the mower did not move and engine die either high or low RPM, Shift to reverse gear, mower moved few inches and engine die. This mower have automatic transmission and the brand is Peerless. I did not use mower for almost 2 years. The drive belt look OK. what should I do ?

faolan, in your opening post you stated, "my wrench contacted both poles on the solenoid, sparked and tried to start (left the key in, in starting position..."... I doubt your wrench "touched both poles". Most likely your wrench bridged from the BATTERY + solenoid terminal (input to solenoid) and the small control (or "trigger") post . In doing this, you caused the solenoid to engage electrically (just as it does when the ignition switch is turned to the cranking position. The fact that it did try to engage sort of hints that a safety interlock switch circuit is open (due to a broken or unplgged wire or defective safety switch), OR the ignition switch itself is defective. You really need to see a schematic to tell exactly what safety interlock switches are on your machine that could inhibit the solenoid (and thus starter) from activating on command. In lieu of a schematic, the usual suspects are "brake/clutch pedal switch", "neutral switch" and "mower blade engagement switch (or indicator)". These switches can be located and "jumped around" with a small piece of insulated automotive wire with about 1/4" of the insulation stripped from each end. Insert the bare ends into the unplugged wire connector (chassis harness side)and try to crank the engine using the ignition switch. As I stated before, your problem could be an unplgged or just loose fitting connector to a switch so check to see if wiggling the connector on the safety switch has an effect on the cranking as part of your investigation.

Try rigging up a gravity fuel tank to your engine, and isolate the stock tank. This might solve the worry about the fuel tank. Also, make sure the breather hole in the fuel tank cap is open--mud wasps love to drop an egg in the leetle hole, and daub it shut with some "poo" until it hatches! Ever see "mud" in little holes in anything that sits outside, uncovered? Thats mud wasp work! Check the spark plug for carbon build-up. It could be the coil/ ignition system, too. I had a lawn tractor here that would run great! I would let it run for a long time, or mow my yards with it, and then it would just shut down, and not start again until it cooled down! Sound familiar? And, a replaced coil fixed it!

@walt2002, hey i was wondering if you were still here, i have read many of your replies and was hoping to hear from you and mownie, you 2 seem to have a wealth of knowledge on these things, i will try the carb first, because it is the easier than the head, but how would the carb cause fire to pop in the carb? im no genius but it seems compression is coming through the carb, and with the few parts in the carb, even no diaphragm, i cant under stand how it would be bad, do they have a ball and spring behind a welch plug like the old model walbro carbs?, i remember years ago when i worked on them a rule of thumb was if you shook them and heard no rattle they were no good, it had something to do with a barometric pressure adjuster valve, you didnt have to adjust the carb in higher locations as you did a b&s carb, just wondering, because i cleaned the carb twice, i put it in a bowl of water while disassembled and used a small straw to blow air through every hole, got bubbles on all, but i will swap them anyway and see, i just want to know what it is, thanks for your advice man