whoop's..two steps backward on D-4

one step forward..after sitting for a couple hours the pony started back up..I guess I will try replacing the condenser..after doing a search on this forum I probably have my bypass valve full of junk from the bad fuel I fed it, so will check/clean that out...

One good piece of advice is to never leave the gas turned on to the pony, when the diesel starts shut the pony down by closing the fuel valve and let it burn the gas out of the carb until it quits, don't use the mag switch to shut it off. Those Zenith downdraft carbs are notorious for letting fuel leak into the crankcase, which can utterly destroy pony motors.

Welcome to the wonderful world of antique machinery 😄

My D4 had a similar fuel problem and it plugged up right at the fuel transfer pump. I simply removed the fuel line going into the pump and flushed all the crap out using the little red tube and a can of cleaner, any will do. Problem solved.

Sorry to call u out Mike, but the problem was not solved as I had to do it again a week later....

😊
CS

I can attest to the gasoline leaking down, same thing happened on my D7, must have left the petcock open. filled it right up and almost out the dip stick tube, old rule of thumb, checking things out before operating certainly pays off, as it would have done in that starting engine. On this model I noticed a plug in the bottom of the bowl, so I put a brass petcock in there, with short hose, turn off the fuel petcock, and drain the bowl with the hose, takes awhile to use up the fuel in the bowl, this is a little quicker and knowing the bowl is dry, no residual trace of gas, can drain down and contaminate the oil, also good to keep that oil changed often.

sidehill,
Regarding the low fuel pressure, there's a bypass valve at the bottom of the filter tower that gets junk in it. Turn the fuel off at the tank and remove the valve and clean it. Sometimes you'll find the spring or rusted. Cat still has the poppet and spring. .I replaced 'em on one of my critters a year or so ago at a cost of around $25 or so as I recall. That solved the fuel pressure problem. There was some discussion a year or so ago so if you do a search on this forum for "fuel bypass valve", I think that will answer that question.

I just rebuilt the transfer pump on two of my D2's. Same pump I think. I was getting fuel into the pump housing on one. The other had really low pressure and I had to do a lot to get the pressure back.

The way the pump is designed, you will know the outer seal has failed because fuel should run out of that drain line that comes out the back of the pump.

The posts above regarding the bypass valve are correct. That can get trash in it that causes it to leak fuel when it should not be bypassing, hence lowering the pressure. Clean out the junk and a quick fix is to pull the spring and make it longer, making it so more pressure is required to cause bypass. I guess this is a temporary fix since the spring must be losing its umph, but it does work to limit the bypass.

There are two seals in the transfer pump body that keep the fuel from getting to the injector housing. I bought parts from CAT to rebuild two pumps and it only cost about $20. You have to pull the drive gear off the shaft, remove the cup and then pry out the two seals. Not a very difficult repair. You have to be careful installing the new seals. It seemed a little tricky to me getting everything back in place and then pressing the gear back on. Needed three arms to hold everything.

On one of my pumps the outer plate was very scarred. I took my mill and milled the face to remove all the marks that were obviously made by the pump gears. I had to do a little hand scrape clean up of the surface and then the pump worked much better.

Regarding your no spark issue with the pony. I had a pony with the exact symptom and it was a bad coil. Spark when cold, none when motor was hot.