Gas boiler control problem

I have a no heat call. The boiler is an older Weil McLain Gold GV (painted blue)the control is a 1013-200 integrated boiler control that had been installed to replace the original, about 2 years ago. It has been working fine until now. When I first saw it the green power light was on and the red limit circuit light was flashing. on call for heat, the control would sequence as normal, but the limit light would still flash and the burner would shut down after 30(approx) seconds and then sequence again. After going through Weil McLain troubleshooting,that brought me to the return water sensor; this older boiler had no return water sensor, and the plug in on the control was blank. I found a blank male plug in for the control, that I assume is for boilers without the sensor, and installed it.
That stopped the limit circuit light from flashing, so I was sure it was fixed. On call for heat, the boiler sequensed properly and I was packing up to leave, when the main burner shut down again, and properly sequensed etc. It keeps shutting down the burner. I isolated the aquastat and flame roll out switch to see if one of them was bad. Still no good. This boiler also does not have a flame sensor. I have one to install, but there is nothing to connect the wire to. The power vent is clear. There is mention in weil Mclain guide of a cast iron block switch, which I see no evidence of. Any help or directions to help will be appreciated. Thanks, Brant