Troubleshooting the Caterpillar 3116 Fuel System
With some water in the fuel the engine was hard to start, but once the tank had an inch of antifreeze in the bottom, then nothing but antifreeze was being delivered to the engine and she died completely.
I cleaned out the fuel tank. Then filled a hose full of clean fuel and connected one end to the fuel line out from the filter and the blew air into the other in order to push clean fuel through the pump and rail. With the return line directed into a beer bottle I could get the engine to run just enough to move her out of the way until I get my gantry built when and can then pull the engine.
- Found the fuel solenoid on the fuel pump and make sure it clicked open when the key was turned on. Put about 5psi of air pressure in the tank and check for fuel leaks, and found none
- Disconnected the fuel out line from the tank a took a sample of the fuel, and also took a sample from the fuel filter and cut the filter apart to look for debris.
- This was some worrisome looking diesel. I am completely stumped as to what the white stuff is floating on the fuel tank. I the posted the photo the Yahoo origamiboats group. Turns out only the top layer is diesel with lots of water in it, and the bottom layer is mostly antifreeze.So now I'm wondering what idiot put antifreeze in the fuel tank. I printed out the photo and took it to MHC, a local truck service station and and Ernie confirmed it was water. When I told him it was from a CAT 3116 he immediately asked if it had used more coolant lately
- The 3116 as well as other CAT engines use mechanical injectors. They are located between the intake and exhaust valves and the work on the same principle. A push tube pushes a rocker arm and the other side of the rocker pushes on the top of the injector which compresses the fuel that is then injected into the cylinder. The fuel is delivered to each injector through a passage that is drilled though the center of the head. Because the work to compress the fuel is done at the injector the the fuel pressure from the pump and through the rail is only 29 to 58 psi depending on the engine speed. The coolant too of course travels through the head and actually passes around each injector that is sealed only by a thin brass sleeve which is pressed into the head. When the sleeve cracks or comes unsealed the fuel leaks into the coolant when the coolant pressure is low, and coolant leaks into the fuel when the coolant is hot and the pressure is high.