Waking up a Texas M151A2

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Re: Waking up a Texas M151A2

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Re: Waking up a Texas M151A2

Postby rickf » July 31st, 2018, 7:35 am

Ok, time to get out of the sun. :roll: :roll:
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: Waking up a Texas M151A2

Postby m3a1 » August 5th, 2018, 10:56 pm

Ok, today I'm going to replace the Prestolite solid state ignition module in my A2 with a Swiss module. For many of you this is an old rehash but for some of you, you might not have ever been inside your distributor at all. So here's a chance to have a look without doing the work. If you've seen it all before, there will likely be nothing new here. If you have not, read on -

Here we go. These are the tools you'll most likely need for the job. The larger of the two flathead screwdrivers happens to be exactly right for the screws that fasten the top cover of the distributor housing onto the lower half. It's blade fits the slot in the screw heads fully, and perfectly. When we're in a hurry, or frustrated, we have a tendency to grab the first screwdriver that comes to hand. Using the wrong screwdriver can ruin an otherwise perfectly good screw head. 3/4" combination wrench is for removing those spark plug wires and for this job, you need only to remove them from the top cover.

A word on tightening these spark plug wires back down. Don't be a gorilla with a wrench. Make sure the threads are clean and in good condition and just run them down with your fingers. Then a light snug with the wrench is all that is necessary to complete the job. You'll see the small screwdriver, the tiny crescent wrench and the pliers in action in a bit.

As Rick will mention in a later post, a nut-driver is indeed the better choice over a small crescent wrench (which is for the nuts on the coil.) While it is true that small, cheap crescent wrenches are the kiss of death for fasteners, mine happens to be a very good quality wrench. Finally, having a small bowl or magnetic tray for all the little fasteners we're going to take out would also be a very good thing to have.

Image

Here's a nice schematic of what we're going to be working on. Take particular note of the bulges in the spring clip in this schematic and where they are. The bulges in the spring clip are what engage the relieved areas in the walls of the lower distributor housing and they serve to hold everything in place. Later in this article, I am going to refer to these bulges as being at the 2 o'clock and 8 o'clock position. Since I take photos at many different angles, to help avoid confusion clock references will be made as the distributor is oriented in this schematic.

If you are curious, "packing" refers to the rubber circumferential seal that keeps the unit watertight at the junction of the upper and lower halves of the distributor housing.

Also note that the figures for tightening down fasteners are provided on this schematic. To tell you the truth, I don't actually use those figures because I don't feel the need to check but when you see something measured in inch pounds, rather than foot pounds....well, I would hope you get the idea. Just be sensible when tightening things down. All we're trying to achieve here is to keep things together, not lift the whole truck off the ground by a single screw.

Image

Fast forward. With the screws removed and placed safely and securely out of the way, and with the spark plug shielded wires detached (from the top cover) and with the top cover of the distributor housing removed, this is what I found. Seems a piece broke off the rotor. Wow. I wasn't anticipating that because the truck ran like a champ. As it turns out, that piece came from exactly where the metal tab is placed on the interior of the rotor. Thus, the rotor worked just fine, even with a large piece of the resin missing.

Call me crazy, but I simply super-glued it back together and put it in the box of used, yet serviceable parts. I'll probably never ever have to use it but "waste not, want not" as they say...

Image

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Note the packing (rubber seal) and how it has a nice curved top face. Not flattened out anywhere, that seal might be good to go but take a hard look at the arc through the 11 o'clock - 1 o'clock position. Doesn't look like it's really completely filling the groove it lays in. So maybe it's not good to go, eh? In my estimation, this seal will turn water away under normal use but would not really be satisfactory for submerged driving.

Mine is an older truck and I wouldn't subject it to submergence under any circumstance so I think allowing the seal to stay as-is, for the time being, is a pretty good bet. All that said, this distributor design is essentially a bucket and it will hold water, or condensation. To top it all off, it gets pretty darned hot in there. If water gets in, it's going to wreak havoc and cost you quite a bit of money to sort it out. If you have a bad seal, or NO seal, seal it up, even if you have to use RTV. Do what ya gotta do. Ok, enough about that.

Observe how neatly the leads from the Prestolite module are stowed, by use of the clamp. Now, loosen the nuts on the coil's terminals. We do those first so as not to have to wrestle with it with the coil loose. Wires first, clamp second.

Image

With the fasteners off, you would think now would be a good time to remove the leads. As this is set up, there is not a smidge more wire than is necessary to put everything together and so, those wires aren't going to want to lift off the terminal posts just yet.

Image

And so, now is the time to remove the clamp. This gizmo serves to organize the leads and keep them out of the way. It also is what helps hold the coil firmly in place, suspending it in the well of the distributor's lower housing.

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With that clamp loosened up and removed, the wires come right off.

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Up and out comes the coil.

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You may have read some comments about potting material in USGI coils. That's the black, asphalt-like stuff there on the bottom. It should be firm. If it is growing soft, that may be as a result of heat, heat created by the resistance in the coil going bad, or exposure to some type of solvent. Having an extra coil in your Oh S**t Kit (even a Chinese coil, which is far better than nothing) is really a necessary part of M151 ownership.

Image

This tang serves as a ground for the Prestolite module, whereas the Swiss module has a third, black wire that grounds to either of the screws that hold the clamp in place.

Image

Here is the spring clip that holds the Prestolite module in place. I am using the small flathead screwdriver to bring the wire out of the retaining groove cut into the wall of the distributor's housing. There are two of these retaining grooves. One located here at the 8 o'clock position and another, located at the 2 o'clock position.

Image

Image

Work it up a bit, but don't yank on it. It's not quite ready to come out yet.

Image

Now tip the Prestolite module up just a bit. You can lift it by the grounding tang. It should tip up easily. If it doesn't, something isn't quite right. Go easy, here. Tipping the module up will allow the spring clip the additional space necessary to come out the rest of the way with ease. There is no tipping of the Swiss module, however. They are a very close fit and only go in straight up and straight down. Notice the tooth, or key, at the 2 o'clock position?

Both the Prestolite and the Swiss have this key, which orients the modules to the precise position required in the distributor housing. Since you are wondering - switching modules doesn't require you to reset the timing. Someone will come along and argue about that, to which I reply - If you have to reset the timing, your timing was off in the first place or your distributor has some other problem.

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And, out comes the spring clip...

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...and off comes the module! Note the rather prominent key at the 2 o'clock position.

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Take a look at the resin on the bottom of this Prestolite module. It is soft and malleable....and yet, this one works fine. Clearly, you don't want your module to be exposed to solvents of any kind.

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The resin on the bottom of this Prestolite module is in terrific shape (hard and flat) and yet, this module works only intermittently. In fact, this is the module where my gremlin lived.

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Now is a very good time for a general tidy up and to make sure everything here moves freely.

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And, it does move freely. Terrific!

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This black lead goes to the capacitor. which is located in that boxy looking bit in the lower right corner of the photo. Think of the capacitor as a bumper for solid state components. During an electromagnetic pulse, huge amounts of energy are released. Your distributor housing acts like a Faraday box but there is a way for the energy to get inside and that pathway is straight through the hot lead going into your distributor. The capacitor collects that energy like a bumper on your car (and yes, I am grossly oversimplifying this) and theoretically, it doesn't allow EMP to fry your ignition components. Pretty cool, huh? You can run these without a capacitor but I keep my capacitor in place because you never know! :wink:

Note the generally clean condition of the inside of this distributor housing. I cleaned it out some time ago. If yours is dirty, DO take the time to clean it out. Do it right and reap the rewards; many happy, carefree miles of motoring....unless, of course, you just prefer tinkering around in your driveway. In which case you should still do it right.

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Here is the new kit which consists of a new ignition module, rotor/chopper, spring clip, clamp and even a new seal for the distributor housing. I like the look of that rotor! It's built like a tank! Also note that, with the Swiss, the resin is on top (facing upward where you can see it) unlike the Prestolite, which has its resin on the bottom.

Image

Time to install. Note the switch (sensor) sticking out of resin of the module. It has a gap in it. That gap is where the choppers on the rotor pass through. Also note the key for properly orienting the module in the housing. (Remember, resin side and wire leads are UP for the Swiss module.)

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And note the keyway in the housing.

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As I said earlier, it is a very close fit...far closer than the Prestolite.

Image

Installation is obviously the reverse process of taking it apart. I do have some comments about the installation.

Putting the spring clip in place is a bit of a bugger on the Swiss module because of the very close tolerances and the larger size of the bulge in the spring clip which makes getting it in somewhat difficult, so go easy. Putting the spring clip in is the time for patience and great care. (I had so much trouble with it initially, I decided to walk away, get something to drink, and then went back to it and that's how things go sometimes.) Wires are organized with the clamp and the black wire from the module goes to ground at one of the screws holding the clamp in place.

I found that the Swiss module had just a little bit more wire than I was used to. Do NOT over tighten the nuts on the terminal posts of your coil. If you are afraid they may come loose, then use a tiny lock-washer and if you don't have one, go get one. This is not the place for Loctite, either. The rotor/chopper goes on just as a regular rotor does but the blade of the chopper is oriented in the gap of the switch/sensor. You can't really mess it up...just be a bit thoughtful when putting the rotor on.

Image

After this installation, the truck was hesitant to start and when it did it was clearly firing on only three cylinders whereas before it was running very happily on all four cylinders. What had changed? Well, chiefly, the relationship between the new rotor and the distributor cap was what had changed. I pulled another top cover, already equipped with a used distributor cap and put that on. Everything ran smoothly after that.

Unfortunately, I cannot tell you precisely what the difference was between the two. So, from this we can conclude that this may be something that comes up when you swap modules. It's not a deal breaker by any means. My point is this.... having another cap, even a used one, might be just the thing to have on hand for a module swap.

Cheers,
TJ
Last edited by m3a1 on September 21st, 2018, 10:45 pm, edited 51 times in total.
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Re: Waking up a Texas M151A2

Postby rickf » August 6th, 2018, 8:28 am

Oh I am going to have fun with this one! Now here is a man who takes great pride in his tools and also pointing out that you have GOT to use the RIGHT tool for the job. He is sure to point out that he is using the PROPER screwdriver for the distributor cap screws. This is the sign of a great mechanic. I love people who show this kind of detail in their work. Now comes the fun part. What tool did he use that was totally inappropriate for the job? I know a lot of you saw it. I know TJ is either cringing or more likely laughing because he knows what is coming :roll: ..................................................... Wait for it :wink: ............................................................................ it's coming :arrow: ........................................................................... almost here :roll: ....................................................................................................................................................................you ready? :twisted:


AN ADJUSTABLE WRENCH ON THE COIL POSTS! :shock: :shock: :shock:

Yup, he did it, big a**ed adjustable wrench on the little tiny brass coil posts! Those things will break in a heartbeat with a small wrench. I always use a nutdriver and I use it very gently on those 200.00 coils!






To anybody new to the forum who thinks I am degrading TJ, Not so, We crack on each other constantly. You ought to see some of out pm's! :roll: :twisted: :twisted:
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: Waking up a Texas M151A2

Postby m3a1 » August 6th, 2018, 9:16 am

Well, none of you are going to have and "wrench envy" with that little guy! It's only three inches long! Hey, three inches goes nicely with two tiny little nuts! It's not the size that matters. It's what your do with it....and I handle my tools so carefully....

:lol: :lol: :lol: Ahhhh... The bon mots are coming so easily today! :lol: :lol: :lol:

But seriously, I have to admit, (and agree) you're almost right, Rick! A nut driver would be the perfect tool but there is one little fly in the ointment. As you know, I have several 151s. Thus, I have several coils (more than a few, actually) and I have found that a few of those coils have nuts that are oddballs, not only in size, but in shape....especially the Chinese ones whose nuts were apparently made by some Chinaman who must look like Quasimodo because he certainly no eye for uniformity. So, I have been proof-testing those coils (they get put in...run...and taken out) and I never seem to make the time to go out and get uniform sized nuts for them. Thus, my go-to tool around here (when it comes to coils) has become that little crescent wrench; one size fits all. A man's gotta do what a man's gotta do! :D

Cheers,
TJ
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Re: Waking up a Texas M151A2

Postby rickf » August 6th, 2018, 11:02 am

Touche, You are on your game today! :lol: Well, I just took out all THREE drive shafts from the motorhome and I am off to the driveline shop. I HOPE they can find the source of the vibration that has been driving me nuts for years now. And yes, I know about the hose clamp trick but at 6 MPG I just cannot afford to keep trying, driving, trying, driving. On top of that this thing sits VERY low to the ground and I don't fit under it without blocking under the tires.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: Waking up a Texas M151A2

Postby m3a1 » August 6th, 2018, 11:07 am

Well, I hope you find the source of your troubles! It took me long enough to get down to this ignition module. Sweet success!
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Re: Waking up a Texas M151A2

Postby Surveyor » August 6th, 2018, 11:49 am

BTDT but always informative posts TJ. Thanks.
1960 M151 Run #1 (working on it)
"She ain't a Cadillac and she ain't a Rolls, But there ain't nothin' wrong with the radio" - Aaron Tippin
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Re: Waking up a Texas M151A2

Postby Mark » August 6th, 2018, 12:04 pm

Ya, I say the same very good post, the pictures very much so Thank you for the info,
mark


1968 m274A5
1960 m151
1981 m151A2
1964 m416
1971 m416
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Re: Waking up a Texas M151A2

Postby m3a1 » August 6th, 2018, 3:32 pm

By the way, some of you may notice I am running a FRAM oil filter on this rig. Rick made some comments some time ago that he thought FRAM was of lesser quality than many other oil filters out there. As luck would have it, I recently saw a video of some guy who took his FRAM oil filter apart and I did NOT like what I saw and now, I share Rick's opinion on the matter. So, next time around, I'm switching to another brand...something other than FRAM. If any of you have an opinion on the matter of what is a GOOD quality oil filter, I'd love to hear about it.

Cheers,
TJ
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Re: Waking up a Texas M151A2

Postby rickf » August 6th, 2018, 3:52 pm

Wix filters are about the best out there.NAPA used to sell Wix under the NAPA name but I don't trust anything from NAPA anymore. Just another Autozone or Advance Auto to me, with the same caliper of people behind the counter.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: Waking up a Texas M151A2

Postby irvin2202 » August 7th, 2018, 1:18 am

Would m3a1 's post not be beneficial to include in the WIKI ?? Great details for future adjustable wrench owners
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Re: Waking up a Texas M151A2

Postby rickf » August 7th, 2018, 8:14 am

It would and he is welcome to add it. I would but I would have to copy and paste I would probably screw something up in the process. plus right now I am jammed up getting ready for a trip.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: Waking up a Texas M151A2

Postby m3a1 » September 21st, 2018, 10:52 pm

I would not presume to be any sort of guru on any topic here so, no, I won't be moving it to the Wiki.. But, If you decide to put it on the Wiki on your own, perhaps folks might be able to find it easier.

Here's an ex post facto report on the work I did replacing that module. The truck is still running strong and never lets me down.

Cheers,
TJ
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Re: Waking up a Texas M151A2

Postby rickf » September 22nd, 2018, 4:00 pm

You shouldn't have said that! :roll: :roll: :roll:
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
rickf
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