I've got a 2000 Murray 42" rider (model 42514x8A) that I bought used from a guy who claimed it worked fine. It starts up every time, and runs like a top in nuetral, but the ignition cuts out as soon as I release the clutch with it in gear or try and engage the blade. I immediately suspected the seat safety switch, but upon examination the previous owner had bypassed the seat safety switch entirely. I checked the PTO and clutch/brake switches with a DMM and they seem fine. I also verified that the wire running from the front to where the seat safety switch was has continuity.

I am stumped. Anyone have any ideas?

Before we do too much diagnosis I'd recommend that you take it back to original standards and reconnect the seat safety switch. In gear and blade safety switches are two separate switches. The only thing I can think of that would kill the ignition when you engage the blade or the gear is the seat safety. Lets start there and then come back forr more help if the problem remains.

I have ordered a new seat safety switch (the previous owner removed it entirely) which will arrive tomorrow. BTW, I am aware that the blade and gear switches are separate; in my case there are two identical switches, one on the clutch/brake linkage and another on the PTO linkage under the gas tank. As I said, they both seem fine.

I will report back tomorrow once I get the safety switch installed.
Thanks!

If I'm on the right track both those switches would work fine. They both would have to go bad at the same time to produced what you describe and that's rare. I suspect he did not jumper the seat switch properly. Some seat switches are open when depressed while others are closed when depressed, he may have done it wrong.

Previously, there was a wire coming from the front that ran out to the seat safety switch in back. The switch was then grounded to the chassis at the same point as the negative battery terminal. The previous owner simply cut out the switch and tied the two wires together.

I have tried running the lawn mower both ways: with the wires tied together and with them separated. With them separated, the mower won't even start.