sounds like you have a problem in the pot circuit
either a bad pot setting or some shorted wiring somewhere.

you can check the pot values at terminals R4 and R5 (with battery disconnected) and get the potentiometer readings.
with accelerator at creep range it should read around 4800 to 6000 ohms. With accelerator in top speed position it should read around 200 ohms or less.

also check the pot wires for shorts to the frame (ground).

there is also a rapid tune up proceedure that shows the general settings the pots on the control card should be set at from the factory, (these may differ from the lift mfg some)
creep - 7 *
c/a - 7
c/l - 5 1/2
1a time - 4
1a DO - 9
Plug - 8
FW PU - 3 1/2
FW DO - 6

I would pay attention to the creep setting mostly as the truck should only be barely moving or wheels slowly turning (if jacked off the floor). You can try turning this back to 0 and see if there are any changes in the speed.
If no change then as i mentioned above there may be other issues with the pot or its wiring or if everything is ruled out then the card may be bad.

The truck is running at full SCR speed.
The bypass command switch checks out and the accelerator potentiometer checks out.
When it first starts and you press the gas pedal, the motors immediately go into full RPM. if you keep driving, about 5 seconds later the two A1 contactors pull in and if you let off the gas they pull back out but the truck remains at full RPM.

Does it lurch and shut down, or keep on going? Also, you didn't answer whether it was closing the by-pass contactor or not.

You can search for the manual Flight Systems has on their web site. EV1 has safe guards that really doesn't let it let it lurch and take off full speed unless the control card is bad.

Yes you do. Directional lever in either forward or reverse, step on the pedal and the truck immediately lurches and takes off.

Don't you have to step on the throttle petal to get it to start moving, not just move the lever to forward?

Thank you for the response. I had one of the drive motors rebuilt because it was shorting. We are on the same page.

By going into high speed, do you mean that the by-pass contactor is closing, or that it's running at full SCR speed?

It's been a while since I've worked on an EV1 30sc, but I'm pretty sure that it will have two switches in the accelerator control box. One for start and the second for full speed by-pass contactor command. Check that the by-pass command switch is working, also check the accelerator potentiometer is working. These checks should be made at the input terminals at the EV card.

You did say this is a 30sc, but said you had "the" drive motor rebuilt, SCs are dual drive motor machines, I want make sure we are on the same page.