Fixing the Army Missile Launcher locomotive - any experience/hints?

I have rebuilt many of the original Postwar units. I haven't done any of the reissues, but am somewhat familiar with the construction of the launch mech.

The typical problem with the postwar versions is multiple rockets firing together, which is caused by the foam under the mechanism decaying.

Sounds like the coil isn't pulling in the armature/pawl that rotates the firing cam shaft. Someone else mentioned the problem in the thread you linked. The Postwar one needs a fair amount of power to fire reliably. I've always used fixed voltage to test end  operate mine. 

There are no Postwar Lionel diagrams for the #44 / #45 missile locos. I think Lionel did something for the modern era ones.

By the way, the plunger pulls in and rotates the cam shaff. Similar to a 3 position e-unit.

What voltage is your transformer set at when running TMCC? Not enough voltage to the track?  The coil does take some power to operate reliably. When a missile doesn't launch, did the firing mechanism trip? Is the foam pad original and not too hard? When you launch in TMCC is the mechanism responding? Can you post a short video of it in operation so we can see what is happening?

The problems I have found is the shock of launching one sometimes will bounce the next missile off it launching cradle. The newer TMCC versions have weak launching springs and just 'dribble' the missile a few inches in front of the launcher. I took the launching mechanism apart and used the springs from a junked postwar 6544 missile firing car. Now it launches the 'Little John' missiles into enemy territory and explode the hidden ammunition bunker! 

Chuck Sartor posted:

What voltage is your transformer set at when running TMCC? Not enough voltage to the track?  The coil does take some power to operate reliably. When a missile doesn't launch, did the firing mechanism trip? Is the foam pad original and not too hard? When you launch in TMCC is the mechanism responding? Can you post a short video of it in operation so we can see what is happening?

The problems I have found is the shock of launching one sometimes will bounce the next missile off it launching cradle. The newer TMCC versions have weak launching springs and just 'dribble' the missile a few inches in front of the launcher. I took the launching mechanism apart and used the springs from a junked postwar 6544 missile firing car. Now it launches the 'Little John' missiles into enemy territory and explode the hidden ammunition bunker! 

Thanks very much for your helpful responses and answering Chuck's specific questions the position is as follows:

1.  It's a fixed command voltage of 18 volts. In case it matters, when I last ran this engine I had an MTH Z4000 but I have since gone over to a ZW-L because of what I had learned about Lionel/3rd Rail smoke units and sine waves. The voltmeters on both transformers have always registered at the highest end of the output range although when I measure it on the track with what I believe to be an accurate meter (I have tried more than one), it consistently comes out at more like 16 VAC. The track and power terminals are K-Line/RMT Super Snap although I used Atlas before.

2.  Yeah, I can hear the firing mechanism engage (coil energizes and the plunger moves) each time I use the F (fire) command but on the first launcher it does not seem to trip whatever mechanism releases the spring. The second time I use the F command the next missile will fire and usually the other two in sequence as well but not always. This made me wonder whether the camshaft was engaging correctly. I did not know that the plunger pulls on it rather than pushes.

3.  I never thought of checking the foam pad but then I forgot that it is meant to hold the various triggers in place. I'll have a look at that. It is original equipment. 

4.  Of course the only video I have saved of this unit in operation is one where it worked as it should (and blasted a special target representing two public figures I don't like)! I had it sitting right on the track with the power inputs. I'll see if I can get another one later in the week.

Thanks again.

I had to take mine apart and clean up all the actuating surfaces and "tune" the latching until they'd fire reliably and not fire two or three at a time.  Now I have it about 99%, maybe once in 20-25 times it may mis-fire or do a double-fire.

I never thought of checking the foam pad but then I forgot that it is meant to hold the various triggers in place. I'll have a look at that. It is original equipment.

The foam pad does more than hold things in place. It applies pressure to the locking mechanism.
On the last rebuild I did, I found it to be beneficial to slit the foam pad between the individual latches, so when the foam was compressed by one latch releasing, it didn't compress the foam under the next latch.

As I write this, I am wondering whether the foam pads that Lionel used on the reissues is too stiff. But if that was the case, the plunger wouldn't be able to pull in all the way, and rotate the cam shaft at lower voltages. 
On the postwar version, the pivot pin for the pawl sticks out of the body for manual firing. You can watch it to see if the solenoid is pulling the armature in all the way.

Well, I can't say I have had the problem of more than one missile firing at once or of one being bounced out of position by another one firing. (Probably should count myself lucky.) But I'll test it with the ZW-L this week and see how it performs - before I start taking it apart. I have had it apart once but could not see any readily user-servicable parts, especially in what I now know to call the solenoid that triggers the camshaft. 

I don't think they thought about service when this was designed, I remember it being somewhat of a PITA to work on.

The FOAM was Lionel's way of locking each firing sequence. It's pretty clever; but the foam doesn't last and dries up and shrinks.  Remember this is not an electronic processor doing the sequencing. . . it's  just foam.  

I think the hardest part of working on these engines is removing and replacing the shell without damaging it.
The front of the frame has slots that are inserted into slots in the shell, right where the bumper begins. Move the frame the wrong way, and the bumper gets broken off.
It's also a tight fit to get the shell over the launch mechanism.

As far as slicing the foam goes: cutting slits should also reduce the pressure to be overcome when the cam is trying to trip the mechanism. Trouble with this technique is if you mess up the slits, you need a new piece of foam.
I use foam window weather stripping to make my own foam. I guess that replacements are available from Lionel or Lionel parts dealers these days. But for many years folks had to make their own.

Well, guess what? I put this engine on a track powered by the ZW-L and the firing mechanism consistently works without a hitch. The amp meter on the transformer jumps up to about 1 amp when the firing coil is energized but I can't see that's excessive. Admittedly the track is an isolated section with power from the A-U terminals but it's several feet long. I think that this narrows down the issue to the power necessary to get the mechanism to trigger and I don't think I have anything to gain by opening up the engine to try to fine tune the mechanism. I can create a siding when I want to "launch" an assault on some target for the benefit of my visitors.

The engine still runs like a dog with no real slow speed control and it derails all too easily. But I guess with the Pullmor motor and the mounting of it on the front truck that's just the nature of the beast.

Thanks again to everyone who responded.