Pony motor issue all over again.

[yrens]

Hey all, its been a long time since i have posted anything thing on here. My last posts I would have to look to see where I was at! Anyway Im back to square one with my pony motor. Previously my issues were that it would run on one cylinder at a time, but not at the same time with both plug wires connected?? Finally the mag failed and I had no spark. So i replaced the condenser no help, cap no help, the points and then all was good!!!! Along with rebuilding the carb before hand.

Fast fwd to now with one successful season of starting and driving the dozer and tweaking and greasing etc. only burning approximately 15 gallons of diesel over the summer the same problem returned
Any input I'll gladly take. What I have done and checked below.

1) good blue spark at both plugs ckd gaps
2) cleaned carb no help
3) put gas in both cylinders no difference
4) swapping plug wire no help
5) cleaned mag cap noticed some carbon erosion at one of the carbon pickup. Cleaned and coated with silicone just to see if any difference, none.
6) cleaned points,looks geat. No help.

Spent six hours and got nowhere covered it up and will get back to it in the spring due to winter coming.


The coil is original along with the rotor disk. The only thing I didn't check was timing which not sure would be off since i never messed with it. Again any advice greatly appreciated. I think whats frustrating is there is not much to it. Two cylinders with a carb and mag.

Jeff
1949 CatD4

 

[1693TA]

You don't mention a compression check on the engine cylinders. You could have a valve either hanging open, or carboned up precluding compression in the proper amount to burn the fuel.

 

[Joel59]

Ask yourself how important it is to you to retain the original integrity of the tractor. The single best change I ever made to an early Cat dozer was to scrap the pony motor and convert to direct electric start. Cat built amazing equipment back in those days, and then started them with washing machine engines! It isn't that hard or expensive, and I can't emphasize enough how "worth-it" it was to me to do!

 

[yrens]

You don't mention a compression check on the engine cylinders. You could have a valve either hanging open, or carboned up precluding compression in the proper amount to burn the fuel.

Yes you are correct haven't done that yet but was and will. I forgot to swing by and pick a compression tester up the day before i went to the tractor site. Last time i checked it was last fall or early spring when i got it running and it was about 70psi per side. The only thing i could do yesterday was use my thumb and they both felt the same amount on the compression stroke. I will take a reading the next trip.

 

[yrens]

Ask yourself how important it is to you to retain the original integrity of the tractor. The single best change I ever made to an early Cat dozer was to scrap the pony motor and convert to direct electric start. Cat built amazing equipment back in those days, and then started them with washing machine engines! It isn't that hard or expensive, and I can't emphasize enough how "worth-it" it was to me to do!

I've briefly thought about it and then thought I wouldn't have ever got this dozer running without the "pain in the ass" pony motor. Reason being, once I broke the main motor loose and everything else prepped it took me approximately 40 minutes to finally get the main started. Since then, usually the first start takes a few before it goes. The only time a direct start would work on " this dozer" is after the initial start and has been driven and all warmed up.

I watched Matt ( Pacific Northwest hillbilly) start his for the fist time and it instantly popped off and started with direct start! Mine would have never or ever do that. When I saw that I was in disbelief.

 

[epirbalex]

Hey all, its been a long time since i have posted anything thing on here. My last posts I would have to look to see where I was at! Anyway Im back to square one with my pony motor. Previously my issues were that it would run on one cylinder at a time, but not at the same time with both plug wires connected?? Finally the mag failed and I had no spark. So i replaced the condenser no help, cap no help, the points and then all was good!!!! Along with rebuilding the carb before hand. Fast fwd to now with one successful season of starting and driving the dozer and tweaking and greasing etc. only burning approximately 15 gallons of diesel over the summer the same problem returned Any input I'll gladly take. What I have done and checked below. 1) good blue spark at both plugs ckd gaps 2) cleaned carb no help 3) put gas in both cylinders no difference 4) swapping plug wire no help 5) cleaned mag cap noticed some carbon erosion at one of the carbon pickup. Cleaned and coated with silicone just to see if any difference, none. 6) cleaned points,looks geat. No help. Spent six hours and got nowhere covered it up and will get back to it in the spring due to winter coming. The coil is original along with the rotor disk. The only thing I didn't check was timing which not sure would be off since i never messed with it. Again any advice greatly appreciated. I think whats frustrating is there is not much to it. Two cylinders with a carb and mag. Jeff 1949 CatD4

Try taking off the rotor and covering the shaft end in insulation tape .

 

[yrens]

Try taking off the rotor and covering the shaft end in insulation tape .

I could try that. Has that worked for you? What would cause the need for that to be done?

 

[Joel59]

On direct electric start, mine only starts unaided on the warmest summer day. However, with a small shot of starting fluid, it takes off immediately in any conditions. I bet yours will surprise you too!

 

[epirbalex]

I could try that. Has that worked for you? What would cause the need for that to be done?

Mine won't run unless its taped , the tape wears after awhile and needs to be done again . My rotor leaks . Does yours have a switch to turn it off ? Suggest you remove the wire from the mag . First start ups after winter usually had the dozer (D7D , D47U's not much better ) started just in time to turn it off and go home for the day , alright following days though . You can set up the mag on a board with an electric drill driving a socket at slow speed to test it .

 

[yrens]

On direct electric start, mine only starts unaided on the warmest summer day. However, with a small shot of starting fluid, it takes off immediately in any conditions. I bet yours will surprise you too!

Maybe,just maybe. She is a cold blooded machine that much I know.

Mine won't run unless its taped , the tape wears after awhile and needs to be done again . My rotor leaks . Does yours have a switch to turn it off ? Suggest you remove the wire from the mag . First start ups after winter usually had the dozer (D7D , D47U's not much better ) started just in time to turn it off and go home for the day , alright following days though . You can set up the mag on a board with an electric drill driving a socket at slow speed to test it .

so your able to slide the rotor on no problem with tape? Do you have spark without the tape? Cause I have spark, just doesn't want to run on both cylinders at the same time. This was the same symptom at the first time I had to get the pony running. Was only able to fix it after the spark finally quit. Then I was able to get it fixed by replacement of the points. With very little time on the points and a good spark Im at a loss.

 

[epirbalex]

Maybe,just maybe. She is a cold blooded machine that much I know.

so your able to slide the rotor on no problem with tape? Do you have spark without the tape? Cause I have spark, just doesn't want to run on both cylinders at the same time. This was the same symptom at the first time I had to get the pony running. Was only able to fix it after the spark finally quit. Then I was able to get it fixed by replacement of the points. With very little time on the points and a good spark Im at a loss.

In mine there was a little brass clip that holds the rotor firm , that needs to be removed , the tape holds the rotor firm . There was no spark till it was taped . Frustration till the penny dropped , all the other things had been checked over and over . The condenser and points were replaced , the condenser was darker than it should have been , I have been told its a crook condenser that causes the points to pit / burn , been told to thats its the coil . A cracked cap will leak as well , crook leads won't help either .

 

[yrens]

In mine there was a little brass clip that holds the rotor firm , that needs to be removed , the tape holds the rotor firm . There was no spark till it was taped . Frustration till the penny dropped , all the other things had been checked over and over . The condenser and points were replaced , the condenser was darker than it should have been , I have been told its a crook condenser that causes the points to pit / burn , been told to thats its the coil . A cracked cap will leak as well , crook leads won't help either .

I don't have a clip on mine and have a spark. Compression and timing are all thats left.

 

[epirbalex]

I don't have a clip on mine and have a spark. Compression and timing are all thats left.

Unless there is no compression that should be alright . You should be able to hear if a cylinder has nothing when the motor is turning over . Timing is easy depending on what drives the mag , if its the key and slot type you can change your leads over to test , while the cog driven one there are dots on teeth to find . I like the big key drive one , if its dark and the x can't be seen its a 50 / 50 chance of getting it right with a simple lead swap and its away . The jets in the carburetor need to be clear and enough flow to the carb needs to be sorted as well . Sometimes it looks like enough petrol is getting there but its just enough to flow to fill the carb while its sitting , check that by allowing the flow through it . Catch that fuel , as its a serious fire risk . Check it for rust .
Sometimes one side can have a weak spark but once the other cylinder gets the motor going it drives the mag fast enough to fire up both

 

[yrens]

I swapped the leads and when i did that it would run at all. I can't believe the points could be bad already after only a few months of use? But its the same game as last time and that is what fixed it.

 

[Dave Neubert]

It takes more power to create spark under compression so you might have spark when the plug is out but not under compression

 

[yrens]

It takes more power to create spark under compression so you might have spark when the plug is out but not under compression

Well that would make sense according to what im experiencing.If thats the case what is your best guess? Condensor, coil or points? Coil I have not replaced yet. Now remember that I can run each cylinder one at a time but not together. Go figure.

 

[epirbalex]

I swapped the leads and when i did that it would run at all. I can't believe the points could be bad already after only a few months of use? But its the same game as last time and that is what fixed it.

You have the timing right if its the key type fitting . If you have had a few months of starting you have done well and I'd be back at the points . Very fine wet and dry paper folded so both sides done at once and it'll be right .

 

[yrens]

You have the timing right if its the key type fitting . If you have had a few months of starting you have done well and I'd be back at the points . Very fine wet and dry paper folded so both sides done at once and it'll be right .

Yeah the timing is key type Bosch mag. Im thinking of just buying a new set and eliminate that before i replace anything else for that fact. Its doing exactly the same as before so I just feel its a mag issue even though I got spark.

 

[bccat]

C

Ask yourself how important it is to you to retain the original integrity of the tractor. The single best change I ever made to an early Cat dozer was to scrap the pony motor and convert to direct electric start. Cat built amazing equipment back in those days, and then started them with washing machine engines! It isn't that hard or expensive, and I can't emphasize enough how "worth-it" it was to me to do!

Cat starting engines are not washing machine engines, far from it, I have started Cat engines in -20f with the pup, where the the direct start machines fell flat on their face, Starting engines where designed to heat the main engine and build up oil pressure for easier starting , it also puts less strain on the main engine. A properly setup and maintained starting engine can’t be beat, used them to load dead machines onto lowboys. Don’t forget these machines are 60- 70 yrs old, now days most people don’t understand these engines. They are very simple If you know what to look for. Do you have a service manual?, Did you put a little oil in the cylinders to bring up compression, is there compression when you turn the engine over by hand?, put your thumb over the spark plug hole while turning the engine over by hand. Are the sparkplugs wet or dry. Do you have electric start on the starting engine. Matter of opinion on the direct start isn’t expensive, horse m**** in my opinion . I would check the spark plugs, I had a lot of problems with Champions, I switched to NGK AB-6 ,
no more problems, also had problems with the magneto coil , would fire outside the cly, not inside. Sorry for the rant about starting engines, it just makes me mad at people that don’t understand these engines.

 

[epirbalex]

Yeah the timing is key type Bosch mag. Im thinking of just buying a new set and eliminate that before i replace anything else for that fact. Its doing exactly the same as before so I just feel its a mag issue even though I got spark.

Its alright to clean them rather than replace , mine have had two layers and once the top layer has been cleaned too many times I then replace them . Usually with Lucas parts that I adapt .