[Al Skierkiewicz]

sanddrag,
The schematic shows a pretty simple wiring job for the feed motor. Both the relays (sometimes called contactors) K1, K2 are fed from a winding on the fan motor. Not sure if the motor is acting as a generator or just has a 24 volt winding. The completed circuit through the handle switch turns on both the feed motor relay (the one you opened) and the main relay which starts the arc and opens the valve for the gas. Please note that if someone has not rewired the control, then the arc circuit is also possibly turned on. Since you say you can hear something clicking when you depress the handle switch, the circuit for the maincontactor, K1 and the solenoid valve appears to be working. There is likely a short near (or in the the connector) marked J1 (handle) on the diagram. The two white wires labeled 5WT and 6WT should go back to the contactor K1 coil contacts. (K1 is the part marked "9" in the block diagram) I suspect that you will find that one of them is connected to S3, the thermal cutout switch, which is part of the transformer. It is likely a simple matter to remove this wire from the transformer and return it to the empty tab on the contactor, K1. Be careful to get it on the right contact.

An interesting side note. If you look at the schematic, the normally closed (NC) contacts of K2 short the output of the feed motor when the handle switch is released. This will cause the motor to stop quickly. The fan circuit is also a safety, if the fan fails and does not provide the 24 volts, then you cannot weld or feed wire.
A picture of the inside of your device might help.