E Units

More information in Lionel Service manuals on E units

The Lionel Mechanical E-Unit is a simple 3 way mechanical switch.  

Understanding how the unit works is important.   Left and right in the description are based on the images below. 

Position 1  Power runs from the pickup to the "left" of the drum,(1) to the "top left" armature brush (3), through the left armature brush through the armature windings and back out the "right"  brush, back to the "right bottom" side of the drum(4) on to the field winding (2) and ground.

Position 2  In position 2, the bottom and top fingers make no electrical contact, interrupting the circuit.  The engine is off or in neutral.

Position 3  Similar to position 1, but the direction of power through the armature is reversed, while the field winding has the same power flow.  This causes the motor to reverse direction.

Power runs from the pickup to the "left" of the drum,(1) to the "bottom left" armature brush (4), through the armature right  brush to the armature winding  and back out the "left"  brush, back to the "right top" (3) side of the drum and on to the field winding (2) and ground.


E-unit including the plunger wiring.

E unit repair

90% of the E-unit problems I have run into are fixed by proper cleaning, a good drum and good contact fingers. 

What do I use for cleaning fluid?  Mineral Spirits and cotton swabs.  I use only a teaspoon amount at a time in little metal cups I have.   A pint may last a lifetime.  It burns so no smoking or open flames around, but you know that since you read all warnings on chemicals you buy, right. I think it is a little safer than the carbon-tetrachloride originally recommended in the service manuals.   Make sure the cotton swab end is tight.  Clean and then use a dry swab to clean off any excess. 

E-unit tools

You can take an E-unit apart and re-assemble it without special tools, but I recommend having the E-unit tool to hold everything in place during re-assembly.

First tip, NO OIL on the e-unit

I have had to clean e-units that had been oiled.  It attracts dirt and clogs them up.   The plunger should move easily and cleanly.  Clean off any rust on the plunger.  Fine sandpaper to get it smooth if needed.   If there is rust on the plunger, you need to check the barrel of the e-unit coil for debris and clean as needed.

The drum needs no oil.  It should have a little drag so it doesn't move, but not hard to turn when assembled correctly.

Age causes problems

The primary enemy of the E-unit is age.  Every pre-war, still original e-unit I have seen needed the drum replaced.  The plastic had rotted or become so brittle the easily broke.  Green corrosion on the contacts is the other problem.  Contact cleaner may help, but be careful, the drum may not like it.   If you tear the e-unit apart and replace the fingers, you may want a new drum also. 

Corrosion and time can also effect the tension on the contact fingers.  I have had the tips of the fingers fall off from wear causing a flashing spark fireworks show as the engine went by.  It lasted a few times around the track. After many attempts I have learned that in 95% of the cases the only way to fix the fingers is to replace them with new ones.     Make sure the new fingers are all at the same "tension" or same alignment.  You should not have to add tension to the fingers if they are level and aligned.  Be careful, even a little bend the wrong way can cause loss of contact.  The drum and E-unit design should add the proper tension.

Age is an enemy to the wiring insulation.  Old plastic coated wiring has the insulation harden and crack off.  The woven-cloth insulation fairs better, but may not be much better if disturbed. 

Buzzing of the E unit

For diesel engines, many like the buzzing as it adds to the Postwar "diesel" sound.   This may be a problem for others.   The buzzing is fundamentally caused by the 60hz AC cycles causing the plunger to "buzz" and toy tolerances.   Many recommend putting a small, thin (about 1/16" .8mm thick) rubber bumper to the top of the plunger is a good method. I haven't tried it yet so can't add any comments yet.

Some use a small full wave bridge to convert power for the e-unit coil only to DC, no or little buzzing of the plunger since it remains constant magnetic direction.  I need to do tests to see if the coil heat/temperature is effected before I comment more on this.

Sticking plunger

On Vertical E-units, gravity drops the plunger when power drops.   Sometimes the plunger wont drop.  First make sure there is nothing hanging it up.   Are the plunger and coil barrel clean and smooth?  Almost anything can cause it to hang up.   NO OIL.    In stubborn cases I have cut off 1/4 of the Horizontal E-unit spring  and used the 1/4 spring to get the plunger to start dropping when power is off.   Be careful if too much spring is used it may drop too quickly at low power when you don't want it to. 

Funny stuff

I did run across one E-unit from an engine made in the 1950s.  It was original but only worked in 1 direction.   I tried everything to make it work forward and reverse.  It never would.  On inspecting the barrel in the switch it was slightly different than a standard Lionel one.   A few months later I came across a service bulletin that warned of this.  Lionel had received a batch that were not the Lionel parts, but the standard ones the supplier made for other things.  The result was some engines had been made with the wrong piece in the E-unit.  How many were made, it didn't say but it was caught at the factory before the complete order had been used.   I was lucky enough to find one and replace the barrel to make it work to Lionel specifications.

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Last update Aug 14 2022