51 M38 - over my head

[Will Johnson]

Greetings I am new (I guess 65 isn’t that new) and a want be mechanic - still working so I have limited time and less knowledge

51 M38 - not started in 25 years - wiring shot but the motor turns, the fluids seem good - my first goal is to see if I can get it started

Has 24 volt alternator, starter, generator, voltage regulator - all to be waterproof, someone has changed the distributor and coil to 12 volt - so I got the 24 volt coil and distributor - that come as one unit and installed that along with the water proof plugs and wires ( hopefully got that right - firing order correct - the timing is probably off)
I have gerry rigged power the coil - from the voltage regulator

Still not getting power to the plugs - (as far as I can see)

My next move is to get the voltage regular harness as well as the connection the coil - just in case my connection to the coil is bad

Too much info yet?

I would love any tips -

I am in Chapel Hill NC - and still working - I would also like to conscider finding someone in this area or even in NC that could work on this - sort of get me a jump start - no sure how much that would cost -

Thanks for any info

Have a Blessed Easter!

[gmwillys]

We have one member on the coast of North Carolina. He is finishing up on his M38A1, and has become an expert in 24 volt distributors.

If nothing else, we can discuss some options to get you up and running. I'm currently starting a two year contract, and will be working 6 or 7 days a week, so time is tight. As a group, we can walk you through this project!

[Will Johnson]

THANKS!
any tips would be great-
don't work to hard - which is my problem as well

[bmorgil]

Love your Jeep Will! I am not at all familiar with the 24 volt system. This forum definitely has two Gent's that I have read, that know the 24 volt G.I. system. gmwillys and LarrBeard for sure.

For starters (no pun intended) I would UN-hook the Gerry rigging. Run a nice clean wire from the battery to the + terminal to the coil. Don't leave this wire hooked up for long periods of time. It will burn up your points. The ignition is now on and hot. With a GOOD spark plug well grounded and hooked to a spark plug wire, turn it over. A better choice is to use a good timing light. No flashing no spark. Let us know how that experiment goes.

[gmwillys]

As a good relevant read, check out Pelagro's "the darn thing is out" series on this forum. The M38A1 and the M38 both use the same military ignition systems. As a collective group we brainstormed through his issue. He figured it out, mostly through trial and error, but he has it down pat now. He kept a good record of what he tried, and what worked and didn't. LarrBeard composed an article in this year's Kaiser Willys catalog that covers bringing a hibernating Jeep back and ready to run. It's a step by step way to cover your bases.

As a piece of advice, I would look into purchasing the complete wiring harness, minus what you have already have purchased. It is expensive, but with all the headaches that come with trying to figure out a cobbled harness, it's worth every penny. Test lights are useless, because the bulb will be 12 volt, but a descent multimeter will serve you better.

[LarrBeard]

THANKS!
any tips would be great-
don't work to hard - which is my problem as well

You have a bunch of little jobs, don't let them overwhelm you.

[Will Johnson]

thanks -great stuff - my gerry rigging was getting power off the voltage regulator - but I wasn't getting spark off the new plugs when I hit the starter - I might not have grounded the plugs enough though I was touching them to the block
I think after reading another comment, I need to get the votlage regular harness and wire for the coil, the distributor lead and give that a try

[Will Johnson]

thanks - I took a look -that was a project! I feel a little better about what I have - but the appears to the same motor
I think I see if I can get the first part of the harness - I think it's called the volatage regular harness and the distrubor lead and give that a try -

it is really a neat machine- the starter is foot activated - hopefully I can get her started - Lord knows where I can go from there

[Will Johnson]

thanks - I am going to see if I get a hold of your article

[bmorgil]

Will, LarrBeard and gmwillys have a good direction to take. Get a voltmeter and the factory manual. Some studying and,that will prevent any more problems introduced by "quick" methods. I want to take back my "hot" wire comment. Get a Multi-meter and check for the correct voltage at the coil. A much better way to go about it.

[gmwillys]

Your engine is an L134 in your M38, then the M38A1 had a F 134 engine. The difference is that the L head is a flat head configuration, with the spark plugs going centered vertical in relation to the head. The F head is configured with the intake valves over the head, under a valve cover. The spark plugs are angled into the side of the head. Both use the same military ignition sets and charging equipment.

Kaiser Willys will send you out a free catalog. I'll look to see if I can dig up the original posts used in compilation of the article.

[Will Johnson]

thnaks - i do have the catalog and read your article - good stuff!
so - I have purchased the rebuilt destributor and coil unit, new plugs and wires for the 24 volt waterproof set up - $$$ - not getting fire to the plugs at least holding one plug to the block to ground it

I did see some posts that suggest the firing order may be wrong - but I have that plugs in order that they were when I got it -

I think i am going to get the lead connector for the distrubtor and the voltage regualar harness and try that -

[gmwillys]

Firing order is 1-3-4-2 .

Here are some helpful links to look through when it comes to timing;

https://www.youtube.com/watch?v=il7nKhbjwVo

[bmorgil]

With the key on, what voltage do you have at the coil + ?

[gmwillys]

24 volts to the distributor. The coil has a resistor built in to keep from burning up the ignition system. As we learned through Pelagro's exploits, the military distributor has to have air flow via the vacuum system to aid in the cooling of the distributor.

[Will Johnson]

I only have a tester that shows current and not the amount - I do have current going to the wire to the coil, but I have a gerrry rigged connection there - going to get that connection

[Will Johnson]

that makes sense - becasuse that assembly is water tight - I will need to see if I understand how that vacuum system is connect to the distributor

you guys have not idea what a novice i am ----- so i appreciate the comments

[gmwillys]

We all learn something new just about every day on these critters. None of us knew about the vacuum system cooling the distributor until doing some research on Pelagro's troubled distributor.

The distributor receives the vacuum through one of two sources on the water proof military systems. One source is via the vacuum pump that is mounted to the top of the fuel pump. Now with that being said, over time the fuel pump may have been changed out with a non double action fuel pump (an ordinary fuel pump). The vacuum pump portion of the double acting pump not only supplied vacuum to cool the distributor, but mainly to supply vacuum for the windshield wipers. Without the pump, you can still use vacuum off the engine, but when you accelerate, the vacuum decreases. When the wipers are in use, they will stop when you accelerate without the vacuum pump.

The second source for vacuum can be tapped into at the PCV (positive crankcase ventilation) valve. On your application, the PCV valve is located at the intake, directly beneath the carberator. There will be a metal tube from there that goes to the side tappet cover. This line can be tapped into with a T fitting to supply your vacuum needed.
Don't be afraid to ask any questions that you may have. There is honestly no such thing as a dumb question. We are here to help, and learn some along the way. None of us are subject matter experts on everything Jeep. It's all problems and difficulties that we have run across on our own Heeps.

[Will Johnson]

Thanks - I will circle back on this topic - as the fuel pump has been removed and willl likely going to get a new or rebuit one - but good stuff!

Right now i am just trying to fire to the plugs - I have ordered the voltage regulartor wiring harness - hopefully getting propper connections to the distributor / coil assembly will get my plugs sparking and i will go from there......

time & money...... - thanks for the info and your time

[gmwillys]

Sounds like a plan.

[Will Johnson]

greeting and Happy new year

without going into to much detail on my M38 53 24 volt

I got new fuel pump, new distrubitor and plugs - I did get it started but it was rougth

I think - my distributor was set incorrectly - so I am trying to re install it with the proper oil pump alginement - getting everything set to #1 plug and TDC (it took me a while to understand that)

my current problem is that the new distributor really won't go in or it won't go down far enought to reach the slot on the oil pump

has anyone had that issue? and if so how did you get it to go?

thanks - I am afraid I am way over my head - running of of time or patience

thanks again for any tips!

[okiemark]

From what I understand, unless the oil pump has been pulled or replaced, nothing changes the timing and the distributor shaft can only go in one way. Maybe someone can correct me if I'm wrong. You should be able to rotate the distributor one way or the other to smooth out the run if that's the problem. Make sure spark plug wires are in the right places.

[okiemark]

Does the distributor housing fit smooth in the block? On the one I'm working on it was rusted in but I got it freed up and it moves smooth now.

[bmorgil]

Will, okiemark is correct. The distributor will only go in one way. The oil pump is geared to the camshaft and the distributor has an offset slot that fits in the top of the pump shaft. The distributor will only go in the pump in one spot. The cam and the pump shaft move together. It is difficult to get it in. Don't give up. Take a look down the distributor hole with a small light and you will see the top of the pump shaft. Insert the distributor and push down gently as you you turn the rotor on the distributor. You will feel it engage the pump and drop down the rest of the way.

The timing can be checked a few ways. But, first I would be sure the wires are on in the proper firing order. Pull out #1 spark plug and take off the timing inspection cover. Put your thumb over the spark plug hole and have someone "Bump" the engine by inserting a socket and a long extension through the bumper and turn the motor over clockwise as you are looking at the fan from the front. When you feel and hear the piston coming up on compression, you should feel and hear the air, you are on the compression stroke. Watch for the flywheel mark to appear. It is tiny and hard to see but its there. There is a mark at 5 deg and 0 deg. As the piston comes up to the top, the mark will line up with the line in the motor plate. You can also insert a 6" long pencil into the spark plug hole and watch it move up and down with the piston. At the point when the piston is at the very top on the compression stroke (TDC), where the rotor is pointed on the distributor is now number #1. Make sure the wires follow the firing order from there. If number 1 is not where it is supposed to be by the book, don't be surprised. Many mechanics stopped bothering with where the oil pump went back in. They just insert the distributor wherever it lines up, find where the rotor is pointed and insert the wires in the correct order from there. It doesn't make any difference as long as when #1 is on compression the rotor is pointed to the right wire, and the rest of the wires are in order from there.

Frequently rough running after distributor or oil pump work is a firing order thing!

[Will Johnson]

thanks guys!! good stuff
right now I can't seem to get the new distrubtor down the point where it end touches the slot in the oil pump - I am temped to take a rubber mallet tap the distrubutor with the top on - the old one fit right in -

part of the story on this jeep - is that it was my fathers (desea - 25 years ago he gave to a friend - it hasn't been run in 25 years but keep in a shed, i purchsed the jeep back from the friend for $4,500 - it had 24 volt regular, generator, alternator - but 12 volt disbributor - so I go got the 24 volt distributor and plug set

hopefully I can get it in - and try out these suggestions

thanks again for the tips
best - will

[LarrBeard]

[QUOTE=Will Johnson;10447]

right now I can't seem to get the new distrubtor down the point where it end touches the slot in the oil pump - I am temped to take a rubber mallet tap the distrubutor with the top on - the old one fit right in -

This is a case where you use as small a hammer as you need - not the "use a bigger hammer" approach. The shaft should fit down the tunnel with no interference. Take the light and look again - there may be something broken off in there.



- but 12 volt distributor - so I go got the 24 volt distributor and plug set

You are to be commended. Most folks would leave the 12-volt stuff in place just because of the cost

hopefully I can get it in - and try out these suggestions

It will go. She's just being a stubborn old beast, paybacks for being ignored for 25 years. Let us know how things work out

[okiemark]

Take a look at the end of both distributor shafts and make sure something didn't break off the old one. If you didn't have any trouble getting it out it shouldn't have.

[Will Johnson]

thanks- not sure I need to be commended - the cost of a new 12 volt everything seemed outway keep what I had

I will double check to see if anything is down the tunnel - but I think it is just that the new is off enough so that last collar isn't going in - Like I said the old 12 volt distributor fits right in - Mike at Kasier said he didn't know it was running as it was set up - so we got the new 24 volt distrbutor

I will keep fiddling with this and see if I can get it to go - I did have in before and it was hard to get it in - but I was not timed correctly so I took it out - but was wondering if anyone had issues with them not going in

thanks again - will

[bmorgil]

Will, there are definitely people who have had trouble getting them out, but I haven't heard of a lot of trouble getting it to go in. If the old one doesn't have an issue, I'd have to guess the new one might be a bit tighter because of machining tolerances. It needs to go in easy enough that you can turn it to adjust the timing. It shouldn't be tight.

[Will Johnson]

I'm back.....
OK - I finally got the distributor in - as everyone said it only goes in one way.....
I think I have it set somewhat right as far as timing - using a pencil in the plug hole and turning the motor until it gets to the high spot and just starting to fall
However - no fire to the plugs - I have power to the distrubtor. If I remove the cover to the distributor and engage the motor - I see an arc as the gap opens - but then no spark on the plugs. I also checked to see if i could get a reading (just a light indicator) if I removed a wire cap on top of the distrubtor - no indication of power

any thoughts? - am I supposed to get that arc? would be condenser be bad (it's a new or rebuilt 24 volt distrubtor with the condensor inside)? not grounded?

thanks - definat

[bmorgil]

Will, are you using a voltmeter or a light bulb to set the timing? If you are and you see the correct voltage across the points when they are open, everything is good all the way to the coil as far as power goes. You should not see an arc. The purpose of the condenser is to prevent the arc when the points open. Going to the basics here, when the points close the coil is energized. As soon as the points open the charged coil discharges through the center electrode to the distributor cap. From there through the rotor to the plug. So if you have the correct voltage across the points when they are open, you can eliminate a lot of things.

[Will Johnson]

thanks!
I am use a light bulb and I do see an arc - so dose that mean I need to repalce the condenser?

that is a new rebuilt distributor - but I guess that dosen't mean the condenser is good

[bmorgil]

Does the light bulb light when the points open? If so you have voltage to the coil. The condenser (though it could be bad) is very seldom "bad". Unless it is shorted, the motor will usually run. Miss-firing and general bad running is the symptom. The points will be badly pitted and "burned" when the condenser is bad. Now if you have power to the coil, the light lights when the points are open, the Coil, Coil Wire and the Distributor cap become suspect. High primary coil current could also cause an arc accost the points. This can occur if the primary coils are shorted in the coil.

[Will Johnson]

Thanks - big time! I am learning -
so I belive this is a matter of the gap being to small and timing
see photos - showing power going to the coil when gaps are open and not when closed - new concept for me -
so I believe I need to set the gap
then the rotor is turned to clynder #4 plug at what I think is TDC based on pencil method
my understanding is the gap should just start to open after passining TDC (top dead center)
this is all new to me - so if I have this wrong let me know

I really appreciate this!!57075708570957105711
best will

[Will Johnson]

I did check the gap - .02 inch - at the most open spot

[bmorgil]

You are correct Will. The points when closed, close the circuit to ground and energize the coil. The instant the points open the coil is saturated with current and has to discharge. It discharges the high secondary voltage build up through the coil wire. You set the point gap first, it will affect the timing. Then you align the timing mark on the flywheel with the number one cylinder at TDC, and the valves closed on the compression stroke. Rotate the engine (a helper is good here) with your thumb over the spark plug hole on number one cylinder. When you feel the air from the compression stroke leaking past your thumb, watch for the timing marks. Align the mark on the motor to the 5 deg BTDC line on the flywheel. Rotate the distributor very slowly and watch the points and the light. The instant the light lights, there is fire to whichever wire on the cap the rotor is pointing to. That is number one. Tighten the distributor down, it is now timed to fire number one, at 5 degrees before TDC. Hopefully number one is where you want it to be. If not, it makes no difference. Just follow the firing order around from there.

If this all went well and there is no spark, I would suspect the coil, coil wire or distributor cap.

[okiemark]

Set the point gap about the thickness of a match book.

[Will Johnson]

thanks guys!

I belive the gap at .02 is to small - going to go up to .03 and try the timing advice

I will report back -
thanks again!

[bmorgil]

The correct gap is .030".

[gmwillys]

A quick farmer's gauge would be a match book cover as okiemark stated. The match strike can also touch up the points in a pinch. Bmorgil is correct, 0.30" is the gap for the points.

[bmorgil]

gm, you missed a zero!

Will, we are both trying to say "Thirty Thousands of an inch."

[gmwillys]

I did miss a zero. That would be one heck of a gap at .30".

[Will Johnson]

thanks!!!

.03 inch - I can't wait to try this - I think that is my problem - may be the weekend before I get back at it......

[Will Johnson]

good morning and thanks guys - I reset the gap to .03 - apparently a bit more and I was getting constant power to both leads on the coil - that is my tester was showing light on both leads as I rotated the motor - and i got no spark to the plugs - or one plug I checked

so i closed the gap to a tight .03 and the light would go off on the one lead as the gap closed - however still no spark to the plug

the plugs and plug wires are new (those confounded water proof sets) - the distributor is new - or a rebuilt one from Kaisers -

I wonder if I should set the gap to .025 inch or could it be that I got a bad coil?

as always I appreciate the advice

thanks will

[bmorgil]

OK Will, check for spark at the coil. Pull the coil wire from the cap. Turn the key on and close the points and open them. The instant they open there should be a solid snappy spark at least 1/8" long from the coil wire across an open gap to ground (a bare spot on the engine block).

[Will Johnson]

I maybe confused - but there is not a coil wire that I can do what - I think that is inside the distribtor cap - this is a 24 volt waterproof system so all the wiring to the plugs is tightly sealed coming off the top of the distributor, if you go back a few posts, you can see what the top of my distributor looks like - I wonder if there is another way to check for this particular distributor weather current is coming off of the coil?

thanks again!

[bmorgil]

Yes it is contained on yours. You can pull the coil and check the resistance of the coils primary and secondary windings. I am not sure what the Military coil should have for value. gmwillys or LarrBeard might know.

If you are getting voltage across the points when they are open and, there is 24 volts or so at the coil between the positive terminal and the negative terminal when the points are closed and no spark at the end of the plug wires, it sure does seem like a bad Coil, Rotor or Cap.

[LarrBeard]

The M38A1 ignition system is a lot harder to work on than the civilian Jeep ignitions because it is sealed and waterproofed. In civilian ignitions, we can pull the high voltage lead out of the center cap of the distributor and look for a spark out of the coil, but in the M38A1 the connection from the high voltage terminal of the coil to the rotor is buried in the cap. That makes checking out the system a lot more difficult, but with a bit of ingenuity – it can be done.

Now, I have to make a disclaimer – I’ve never seen one of these in person; but I did stay in a Holiday Inn Express one night or two and I’ve read what people who know what they are doing have written about this thing. Let’s look at the attached picture I found and try to understand just what is going on here.

The normal distributor things are located on the upper right of the picture. The lower left is the coil, buried down in this little waterproof housing. The whole distributor is tied into the vent system by the vent line at the lower left corner. This is not a vacuum advance line, just a waterproof feature. Power from the 24-volt system is connected to the threaded connector at the lower middle of the assembly. The square box is part of a radio interference filter (it is a capacitor – but not THE condenser. )

The center pin of the threaded connector goes to the lower terminal of the coil. If you use your continuity tester, it should light if you go between the two points. With the ignition ON there will be 24-volts on this terminal. (You probably will need a voltmeter to check this; a 12-volt test light may burn out if you apply 24-volts.) The upper terminal of the coil goes over to the points. (You can see the points; we have talked about setting the gap to 0.030 inches when the lobe of the rotor is at its peak.) That terminal has a wire that connects to the screw terminal where the rotor is pointing. The wire of the condenser connects here as well as the arm of the point assembly.

If you put a test light on that screw, you will get a voltage (light ON) when the points open and nothing (light OFF) when the points close. You can verify this as you have a helper crank the engine. This ON-OFF verifies that the points are opening and closing. If you have a voltage on the lower terminal of the coil and no voltage at the screw as the points open and close – you probably have an open coil. An ohmmeter can verify that – the 7-dollar Harbor Freight meter.

Once you verify points opening and closing, it’s time to try to check high voltage out of the coil. The high voltage terminal of the coil is inside the two circles in the middle of the picture. Here is where my ignorance comes into play. I do not know if the bottom of that well is a solid metal contact, or if the little hole is the only contact, but somewhere in there is the high voltage contact. But, if I look at pictures correctly, the whole well is the contact.

Get a normal spark plug wire, with contacts on each end. By whatever means you need to do, rig up a connection that plugs into that center terminal of the coil. A normal spark plug wire just might plug in, or you may need to strip off a bit of insulation to get a piece of bare center conductor, fold it back and wrap aluminum foil around the wire until it plugs into the hole. Or, just wrap the connector on the wire with foil until it plugs in. This is Jeep engineering at its best! Once you get that done, have someone crank the engine. You should get a hot blue spark that will jump 1/8-inch or so to the engine block.

If you get that spark, you have a good coil and points. If no spark here, you may have a defective coil. Next, check the cap well. Pictures I see seem to show a contact pin that plugs into the high-voltage terminal of the coil. There is a connection over to a contact that rides on the rotor tab. Make sure that those are clean and connected.

Once you have done that and get good results, you should have spark at the plug terminals. Use your test wire to check.

I hope this helps. Keep us in the loop – we feel your frustration – we’ve been there too!

[LarrBeard]

As a group, we take these topics and use them for an excuse to go do some studying on our own. Well, BMorgil gave me a research assignment so off I went.

As with just about anything on the ‘net, there is a bunch of stuff that you have to take with a grain of salt, but the g505 Forum has the best source if you can sort through it.

There is a LOT of chatter about after-market coils, the summary of which is that they tend to be junk so many times you are much better off with a NOS or even Old-OS GI-coil than an after-market, Made in China rip-off. I found an image of a 1950’s Prestolite Service Bulletin that talked about 24-volt ignition systems as they applied to the M38-series vehicles.

The two things we were most interested in were the primary and secondary winding resistances. It was interesting to note that these readings are for a coil at room temperature, about 75-degrees. A hot coil just off an engine will read differently, but no specs were given for hot/cold conditions.

Primary resistance (measured between the two terminals with nuts): 6.2 to 6.5 ohms

Secondary resistance (measured from center terminal on high-voltage connector to case): 10,000 to 11,000 ohms.

Isolation between primary and secondary: Not specified, but should be beyond the range of any handheld meter – many millions of ohms.

Two other specs that showed up, just for information:

Value of the “capacitor” in the 24-volt input radio interference filter: 1.8 to 3.0 microfarads

Value of THE CONDENSER: 0.18 to 0.22 microfarads (same as a 6-volt or 12-volt system).

In each of these, their DC resistance should be many megohms.

Oh by the way, look in the bottom of the coil well. If there is oil in there, the coil is leaking and it's toast. Just to add to things, old OEM coils probably had PCB's in their insulating oil.

Now we know a few more things about the M38A1!

[bmorgil]

Nice stuff Larry! On its way to the Tech Section.

[Will Johnson]

good stuff - thanks!

I have tried putting my light bulb meter on that center well - and have not gotten a reading - it seems as if when the gap points are open - that should be giving a reading - do you think I should try your other method of checking?


to me it seems like I have a bad coil - seems unlikey since this a new rebuilt distribtuor - but as I am reading your notes - it may well be bad

thanks again - I appreciate the notes and encouragement!

[LarrBeard]

"I have tried putting my light bulb meter on that center well"

Even if the coil and points were working perfectly, you would not see anything with the light. But,if you got a jolt that knocked you on your backside - that would be a good sign.

[Will Johnson]

I got a new coil -same results....
Dumb question first - as I am getting readings with my bulb test across both sides of the coil - that power is gong to a the condenser and then to the rotor - right? - should I get a reading on the end of the rotor? I am not

I am thinking when the rotor hit the contacts the circuit is complete and shoots to the plug - but it seems the grounded light bulb would do the same

When turning the motor and watching the gap opening, it doesn’t appear to open when passing the contacts in the cap of the distributor- and I can’t turn the distributor enough to make that work. It seems that gap should be open as the rotor is passing the contacts -

Could the distributor be set wrong?

I think the distributor could only go in one way - but perhaps I should put it and try to reset another way?

I see some stuff about resetting the oil pump but that seems like a big job and I don’t think this one has been altered

Thanks again!

[bmorgil]

Will, I don't know if you have seen this but start here. https://willysjeepforum.kaiserwillys.com/showthread.php?2277-TM9-8014-1-4-Ton-4x4-Utility-Truck-M38A1-and-1-4-Ton-4x4-Front-Line-Ambulance-M170 Page 167 begins the Ignition Section for the M38 24 volt ignition. This is the A1 but I think it is the same for all the 24 volt systems.

The basics are this:

When the ignition is on 24 volts positive is applied to the positive side of the coil Primary.
Think of the coil as two parts, one side makes energy the "Primary". One side discharges this energy the "Secondary". There is more to it than this but, think of it this way.
The points provide the Negative "ground" for the coil Primary. Think of them as a switch to ground.
The condenser provides a clean voltage break. It does not handle much current. Unless it is shorted, its not the problem.
When the points close the coil's primary has a complete circuit and the Secondary side "fills with Energy (voltage)".
The instant the points open the storage of energy in the secondary side of the coil is so large it must exit somewhere.
It needs a path to ground. It discharges this energy out the coil wire and into the cap.
The rotor is the director of the energy pulse. The coil wire transfers the energy to the rotor. Wherever it is pointed, the voltage is headed that way.
The spark plug wire takes it to the plug where the energy is dissipated across the gap of the plug to ground (negative).

If you look at the circuit diagram, use your meter to be sure you have the correct voltage where it needs to be.

[Will Johnson]

Thanks - I have reading and stuff to check and report back

Thanks for your patience - and sharing of knowledges

Best

[LarrBeard]

Thanks - I have reading and stuff to check and report back

Thanks for your patience - and sharing of knowledges

Best

The high voltage spark from the coil (the contacts in the center) get carried from those center contacts to the rotor by a bar in the distributor cap. With the cap off, there is no connection from the high voltage to the rotor.

As the rotor turns, it does not actually contact the connection to the individual plugs; there is a small gap that the spark jumps across from the tip of the rotor to each plug terminal.

Your light won't tell you anything on the high voltage (secondary) side.

[Will Johnson]

https://willysjeepforum.kaiserwillys.com/attachment.php?attachmentid=5853&stc=1https://willysjeepforum.kaiserwillys.com/attachment.php?attachmentid=5854&stc=1https://willysjeepforum.kaiserwillys.com/attachment.php?attachmentid=5855&stc=1

thanks for the info! so the power somehow goes up to the cap - I am betting thru the hole in the middle of the coil - via a spring in the cap - then out to the contacts in the cap - correct?
not sure I completely understand - but somehow the rotor makes contact with those contacts in the cap and then out to the plugs

If I am off base - let me know

It seems looking at when the gap is open and I am getting the power to the contacts, they are past the point where they would be hitting the rotor -
I can't adjust the distributor to a point where that would

this why I think the distributor may be set wrong

check my photos -

thanks for your knowledge and patience

stay safe

[bmorgil]

Will, I think you have it. The rotor "sweeps" past the contacts on the cap. They are seldom lined up perfectly. As Larry pointed out, they do not actually touch. When the spark travels via the "Bar" (or coil wire in a non military), from the coil to the cap (the instant the points open), The energy travels down the cap through the center electrode. From there it travels to the rotor directly through the rotors contact at the middle. It then travels across the rotors electrode and whichever Distributor electrode is closest, it travels to. Then out the cap and so on to the plug the rotor is pointed to. As you adjust timing, you move the position of the rotor in relation to the points opining point, retarding or advancing the timing.

First set the point gap, then set the timing. Check the firing order. Keep us posted!

[Will Johnson]

thanks - I am starting to understand - I assume this concept work on old tractors - I also have a 50's International Harvestor tractor my son is working on - I am hoping I can use what I am learning on that

back to my issue - I have the gap set, and firing order - but the I can't get the timing right - the distributor won't advance or retard enough either way for rotor to be in the direction of the cap contacts, when they are in the open position.

that is why I think I have set the distributor incorrectly or perhaps the oil pump is set wrong...

thanks again for your help!

[LarrBeard]

I was finally able to find some good pictures of the M38A1 distributor cap. Yes, the spring fits down into the “hole” terminal of the coil and there is a bar in the cap that brings the spark over to the little button in the center of the cap. That button rides on the tab atop the rotor.

[bmorgil]

Same concept as "the old tractor" as long as it's a gas engine! I have an IH 184 low boy in the barn.

[bmorgil]

back to my issue - I have the gap set, and firing order - but the I can't get the timing right - the distributor won't advance or retard enough either way for rotor to be in the direction of the cap contacts, when they are in the open position.

that is why I think I have set the distributor incorrectly or perhaps the oil pump is set wrong!

Will, mark the number one spark plug terminal location on the distributor so you know where it is with the cap off. Take off the cap. When the points just open (light lights), the rotor MUST be pointing to number one, when the Timing mark is at the 5 deg before mark and the engine is on the compression stroke at Top Dead Center on number one cylinder. Make sure you have this condition. If you do it is timed correctly. If the rotor is not pointed to number one, move the wires around until it is and the order is correct. With the rotor now pointed to number one and the firing order correct it should run just fine. There is no "law" that says number one has to be in any particular location to run. It will work anywhere as long as the rotor is pointed to a plug wire headed for number one. If you have the light lighting when the points open, there should be spark. How are you checking for spark?

[Will Johnson]

Thanks -you may be on to something as far as moving the wires around - keeping the order - I can’t wait to try that

I have been checking for spark by holding plug against the block and looking for spark when the motor gets cranked

I will report back

How did you guys get so smart?

[LarrBeard]

"How did you guys get so smart?"

We made the same mistkes so many times we fugured out how to do it right - or at least some way that works.

[okiemark]

No kidding.

[bmorgil]

Not smart, old.

[5JeepsAz]

Old, not smart, but happy!

[Will Johnson]

greetings youngsters!

still no luck...... I did mark the sides of the distributor - where the contacts on the cap are. Here is what I think is the problem. When the rotor passes that point where the gap is open, it is not at the contacts on the cap. I took the distrubor out and checked, turned the rotor, as that contact point passes the contact location on the cap, the gap is closed, just after it passes that spot the gap starts to open. Does that make sense? - that seems to be something fixed from the factory - or is that something I can adjust or should I see about getting another distributor?

thanks again! best will

[bmorgil]

Will, this is getting harder as we go over the internet. Can you take some pictures of what is going on? There really isn't much to these things. Bring it up on number one compression stroke Top Dead Center. Rotate the distributor back and forth, and take a picture of where the rotor is pointed when the points JUST open and the light lights or the meter shows voltage across the points. Lets see if we can't get a general idea of what is going on.

Remember that the instant the points open the spark is generated. As long as the rotor is within a few degrees of the post on the cap for number 1, it is where it is supposed to be.

[Will Johnson]

thanks - will do - eventhough I am old enough and should be retired - I am still working - so maybe a few days or weekend before I get this back to you -

thanks for the brain power!

best will