Well, Case backhoe troubles actually. I think it's a CK 74. Anyway, here are the symptoms: The 1970s engine (gasoline) starts right up, idles well, and runs OK when it's not too warm. After fifteen or twenty minutes it starts running poorly. It misses badly. If I let it die it is very hard to start until the engine has cooled some. What I have done: replaced the plugs, rotor, cap, coil, and wires. At first I thought it was the coil. I had another laying around so I swapped coils. This seemed, at first, to solve the problem. When I replaced the plugs the only brand available on the island that were the proper type were Champion plugs. I have been told by several mechanics to avoid Champion plugs. The old plugs were Champions and they looked like they were burning correctly when I pulled them. Now maybe the replacement coil I had kicking around is junk and I need to get another one, brand new. The ignition system uses a ballast resistor and the coil is just warm to the touch, not hot like it would be if the coil was wired wrong and getting the full 12 volts all the time. I checked that too. The ballast resistor is only bypassed when the starter motor is energized. The engine is not getting so hot that it boils over, in fact, sticking my finger in the radiator neck to feel the coolant temp tells me that the engine really isn't running too hot. Steam and bubbles don't come out of the open radiator neck when the engine is running so I don't think I have a bad water pump that is letting the engine cook while the coolant in the radiator stays only warm. I do have to run the engine with a little choke for it to run half way well. I have adjusted the carb, which is a very old design similar if not exactly the same as the one on my '39 Ford 9N, according to the directions for this type of carb. That seemed to help some, but even if I adjust the carb so that it runs rich I still get the missing problem after the engine has run for 15 or 20 minutes. I am going to buy a carb rebuild kit but I don't expect it will fix the problem. So, any ideas? I'm stumped and I know there several folks here who know about old engines. Thanks, Eric
- posted
11 years ago