Hi, the 333 marx was a good engine , i worked on restoration of lionels and marx for over 28 years. that 333 is a simple engine. here are a few tips . clean the e-unit rod and it is easy to remove to clean using some blue magic metal cleaner found at walmarts and auto parts stores. also put some cleaner on a q tip and spin it in the e-unit bore get that clean , check the e-unit contacts if not clean use the same cleaner very gently to clean the contact points. the check your motor brushes if in question buy new ones and clean the bores out same method then check the brush plates [ commutataer] and clean it also and check for warpage from over heating. then check all solder joints for cold solder or loose connections . 1 other thing to check is the armature for shorts. simple to do use an ohm meter from the brush plates to metal armature plates. you should not get any reading , then go from brush plate to brush plate make shure you get a circuit. then check after you remove the armature check inside where you took out the armature for any wires that could have worn insulation. good luck , TM
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