Do you mind posting the info on your spark tester? I seem to have more and more trouble seeing a spark jumping a plug gap. Plus, many small engines have hardly enough plug lead length and room to even put a plug in it when it’s not screwed into the cylinder.

"Neil" wrote:

There's a couple of really good places that rebuild mags - they come back looking like new. The one I've used twice is Mainely Magnetos in ME. You'd swear my RC-2Q was brand new off the shelf, and it worked exactly like the book said.

How much did they charge to do your mag Neil, and what did they do, like was the coil rewound, and the armature too? It's almost a year since we enjoyed lunch together at Niagara Falls, hope you are going well!!

One thing that confuses me about the problem we are helping fix is the mag was supposedly serviced and tested already by a respected mag guy wasn't it?
Thanks
Mike

i had similar problems on my D4 pony. all went away when i replaced the spark plugs. also check to make sure that a mud wasp hasn't plugged your intake.

Spoiler alert. IT RUNS!!!!

I have been busy at work for the last 2 weeks, and finally got back to it yesterday. My father and a friend's father-in-law of his that owns a 7J D2 came out. He brought with him a spare mag and a spare carb/venturi setup. The other mag was a WICO XH 1907. That is the direct replacement for the Eisemann RC-2H. Anyways, we put that on, and it would now cough and sputter, but still not run. We swapped the carb/venturi setup, and same thing. At this point, I am starting to get really frustrated, thinking that it has to be something stupidly simple that I have overlooked....

So at some point since this pony ran last, (probably 15-20 years ago,) someone put a new intake manifold on the diesel engine. According to my parts book, and the pictures of other RD4s I have seen online, the pony motor exhaust should blow right out the side of the engine. This is not the case. The diesel engine has a NEWER intake manifold on it that is designed like a tube-and-shell heat exchanger to preheat the diesel intake air charge with pony motor exhaust. This obviously requires a different exhaust pipe for the pony that was on it. Well, when someone did the transition, they did not open the other end of the intake manifold up and put the rest of the exhaust on for the pony, so essentially the exhaust was dead headed....

When I first discovered this, we couldn't believe it, so we pulled the exhaust pipe off the pony, and tried firing it. It started right up, no questions asked. Fast forward an hour, and we had removed the plug when the exhaust from the pony should exit the intake manifold for the diesel engine, and put everything back together with the exception of still using the WICO mag instead of the Eisemann. The thing fired right up and purred like a kitten at idle and higher RPM.

I will attach pictures of the intake manifold that that is on the diesel showing the plug we had to drill out. My next job, (probably next weekend,) will be to swap back to the Eisemann mag to see if that will run the pony motor, or if there is still a problem there, because withe the WICO, it was coughing even with the exhaust plugged up, when the Eisemann was doing nothing.

I sure hope this helps anyone else who is having pony motor problems. There has been a HUGE amount of information put into this thread by lots of very knowledgeable people. I will keep people updated on how the project goes. All the fluids and filters are going to get checked, changed and cleaned before I fire the diesel up and drive it out of the shop for the first time in 5 years.

Hi Jake,
to the best of my knowledge there is no other outlet for the pony exhaust on that style manifold--the elbow at the radiator end of the manifold is for the Diesel engine air inlet and where the Diesel engine air cleaner system bots on--The inner pipe/inlet manifold is separated from the pony exhaust and so receives its pony exhaust heat assist for easier starting, but is separate from the Diesel Inlet manifold so the pony exhaust does not contaminate the incoming Diesel filtered air.

They likely thought that dirty air was getting into the diesel engine and blocked it off--pony likely never ran again and the Diesel was started by towing. Parts Book says 3 L-2288 Plugs--2 others are around on the back side of the manifold from memory.
Left field issue caused by the unknowing. Well Done those men for sorting it out and, thanks for coming back to tell us your finding as it adds to the list of oddball issues.
Cheers,
Eddie B.