I've got a 1956 Caterpillar D8 15A series G that I'm trying to get running again after sitting stuck for about 7 years. I did have it running twice during that time but maybe 30 minutes total. Prior to this I have ran this dozer clearing my land so I know it's a decent runner. I'm trying to reprime the fuel system. At some point in the past the torque converter was replaced and new fuel lines ran so it's slightly different from factory from what I can tell. I pressurized the fuel tank and spun the engine over. I'm getting fuel to the torque converter fluid filter housing and also leaking a lot of diesel at the converter from somewhere. I can not get any fuel up to the filter housing on the injection pump, but I do get sir when I pressurize the tank. Im not sure which line is supplying fuel to the converter and taking fuel away. The T fitting in the upper left of the first picture goes to the back side of the converter. The line runs as follows Leaves fuel tank the T fitting to the back of the converter Other side of T fitting to fuel pump under injection pump The 2nd picture that line comes from the torque converter filter housing and starts at the fuel pump under the injection pump. I would like to isolate the torque converter to try to get the engine primed and running first using a pair of valves and when I get the engine running open the valves so the entire system can flow. Here's a clip of getting my D8 out a few after I had gotten it buried to the top of the tracks seven years ago. Only took a PC400 to get it out.
I am not familiar with the CAT fuel system but I don't know of any reaso why fuel would be supplied to the Torque converter
They were fuel torques they used fuel in the torque instead of oil haven’t heard anything about them in years
Hopefully @Old Magnet sees this thread. He is one person likely to have the information you are looking for.
I was thinking seem to me there is a bleeder on the torque maybe you have a big air pocket in torque
if the torque is leaking it is most likely keeping you from getting primed i would run a line from the tank to the filter housing. i tried to get parts for a D9 convertor but had no luck junked the 9 because could not repair
Yes, there is a bleeder,
Here's some info on the fuel system......
Learn something new every day! What was the purpose of this type of fuel system design?
the torque convertor uses diesel instead of oil to make it work
Goes back to early day applications of torque converters, looking for higher torque outputs prior to Cat Powershift transmissions. Cat used a "Twin Disc" three stage torque converter along with a special conventional type clutch. Diesel fuel was acceptable as a fluid when it still had lubricating properties unlike today's modern fuel. Unfortunately Cat left out the reserve tank portion that recaptured seal leakage opting to just let it leak to ground.
I had one of these machines in a fleet of old equipment. It leaked as well. It had another issue that I never solved as it was spare iron and seldom operated. The converter ran cool when pushing heavy loads continuously. If you were just walking from one place to another it would overheat something terrible. I was told by one old timer in those days that this wasn't really a torque converter but actually was a fluid coupling. Don't know if that was true or not. I had enough issues with old machines that actually had to run all the time so this never got looked at seriously.
We had the same problem on a Brown Hoist RR 150 ton crane, that we rebuilt, Cat D337f with a Twin Disc torque, torque ran hot While traveling, finally we hooked a box car to it , ran cool, they used it sparingly for a year or so, then it was donated to a museum, I was told the engine is stuck, this was in the late eighties sad indeed, cheers
How hot are we talking about? 250 deg F. is tolerable for limited time?
those 3 stage diesel fuel charged twin disc converters had a narrow working band. The torque converter needed to 'work'. Too low a load and they would overheat and same with an extreme load. But they had massive torque multiplication, 5-1 in many cases. Because they needed to work the transmission gearing in the likes of D8 15A and 35A and D9 19A and 50A was fairly fast; 1st gear in those machines was 3.5 mph . they were phased out around 1961 when cat went to single stage oil charged converters .
Found this info amongst my stuff!!!!!
and page #2......
Are there any accessible parts pages that show the internals of those converters?
I have a lot of diesel running out of the bottom of the converter housing. A decent steady stream. I tried putting air in the tank and could never get fuel up to the filter housing on top of the injection pump. I do however fuel running in line #20 between the tank and transfer pump. This afternoon I tried adding an electric pump in line on the #20 line and still no fuel into the filter housing. Seems like I have two different issues to overcome. #1 converter leaking diesel #2 some sort of internal issue with the fuel pump.
That would be interesting. I have a 2nd converter that I was told was junk and was thinking about opening it up to see what's going on.
The Service Manual for the 14A/15A does a pretty good job of showing the torque converter innards. If the TC seals are shot that's a bit of a problem although I believe I heard they are still available from "Twin Disc" for a "ransom".