It's normal for the wire loop resistors connecting the glow plugs to glow red (this can more easily be seen at night). The early 300D's have the "loop" style glow plugs and the connecting wire loops are part of the circuit. The later 300D's have the "pencil" type glow plugs that have individual wires running to each glow plug. The wires running to the pencil type GP are large diameter wire to handle the current flow.

Check list for hard starting problems:

battery (a new battery must be charged up before using since it has been sitting on a shelf for who knows how long);
charging system not working;
starter turning too slow;
glow plugs not working:
fuel system flow impaired (change fuel filters, clogged fuel line, algae in system, etc.);
fuel pump pressure low;
fuel pump check valves and/or springs failing;
bad fuel;
air leaks in fuel system;
water in fuel system;
wrong oil viscosity (too high like a straight 40W);
restricted air intake flow (badly clogged air filter);
injection pump return fuel line check valve spring collapsed (take out and stretch to ~ 25mm);
injector nozzles failing;
injection pump start of delivery is out of spec;
valve adjustment needed (low compression if too tight);
low compression.

Good Luck!
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.