Hi i have a 1954 ht4 traxcavator with a 7u motor HELP please

Low pressure at the injectors means the injection pumps are not responding to throttle position. Take the side cover off the injection pump and check that the rack is actually moving in response to the throttle and the lifters are actually moving..

I agree with everyone else, it is most likely not injecting fuel or not injecting it at the right time.

Always possible you have very low compression related to valve timing (did you have the camshaft out etc?) or valve adjustment. With the valve rocker covers off you can ensure the cam is timed to the crankshaft and the valves have about 0.012" clearance. But I guess if it will run on transmission fluid it has decent compression.

While you have the cover off the side of the injection pump housing to check that the rack is moving etc, if all that appears to be ok, you should at least do a rough check that the appropriate lifter rises as each cylinder comes up to TDC. It takes a depth mic to set them properly, but with unknown history on an engine you might find someone has timed the engine 1 turn of the crankshaft off. Sometimes things like that get missed in a change of ownership.

It is also possible that the engine is timed wrong because the flywheel is installed incorrectly. Flywheels on that age machines will go on equally well in any of 6 positions. There is only a chisel mark on the crankshaft flange to mark how it should be installed. You can pull the injector from #1 and run a wire down the precombustion chamber and touch the top of the piston the check the flywheel marks are lining up correctly.