John, thanks for the recommendation (head swells)[especially coming from someone I think actually knows the difference]. BUT I do prefer that I answer on the forum, so that it is Google search-able and someone else with the same problem may benefit from the answer at some later point in time.
I DO try and give other folks a chance to answer some of these posts, if they want to, it is not my intent to monopolize the conversation.
I agree with everything 7777 offers up and while a serial number often helps, the description of the carb is good enough so that I know this is a tier 1 (2003) forklift at82d serial number series. (so it would be the electric lockoff) and of course, the first steps in troubleshooting an IC unit is (still, with or without computer controls) to find out if it has spark and/or fuel getting to the combustion chamber.
In this case, I would first recommend that you do NOT test the red and white wires at the vacuum control valve (mounted on a bracket on top of the regulator) as they are a pulsed signal to ground, and testing them with a test light or a meter may have just the circuit to let the smoke out of the ECU and then you would have the problem you describe as soon as the smoke clears.
I would also ask that 7777 and ed_h consider adding their e-mail addresses to their -profile-, so if someone wanted to send them something via e-mail, it would be possible to copy-paste a properly formated address.
When ed_h says "shot a little starting fluid down it and it fired right up" does he mean it ran until the starting fluid/fuel was used up, or it kept running until the key was turned off?
Has anyone messed with the accelerator pot? if so, it may have to be set using the computer program to set both the high and low sides of the pot, as this unit will not send a signal to turn on the fuel lock off or to open the throttle butterfly if the pot is too far out of normal setting, or has not been set up properly. also, has anyone pushed down on the accelerator pedal linkage without the floorboard installed? since that can also cause the ECU to consider it a problem with the pot reading being too far out of setting and may shut down the engine.
ALSO on this unit, there is what looks like a cable lug on the manifold mounting stud, that has 2 black wires into it. this is NOT a wire lug, it is a sensor for the engine temp to the ECU and putting those 2 wires together can cause this unit to not start (the ECU will consider the engine to be overheated to the second stage and shut it down).
These also do have a rod/valve in the lock-off/filter assembly that can get stuck and prevent fuel from flowing into the regulator, that I think was what 7777 was getting to when he mentioned "there are easier ways to check".
7777 used a blocked word where his post shows "****" and that word rhymes with truck, starts with the letter s, has 4 letters (or 5, if plural, as used here) and means "to draw a vacuum like we do through a straw".