1 Troubleshooting a 1985 K100 that won't start/stay running Wed Nov 11, 2020 6:36 pm
TrailKlaus
active member
According to the previous owner, he had the bike running (after having replaced the fuel pump and probably cleaned/replaced the fuel injectors), and had taken it out for a test drive. He had it idling back it his place, when a fuel injector (apparently not adequately clipped in place) separated enough from the fuel rail to start leaking fuel, from a which a small fire occurred. This somewhat damaged the wiring harness in that area.
My efforts: The previous owner gave me a replacement section of wiring harness that I was able to use to replace the fire-damaged sections (being the wiring to the fuel injectors principally). I made sure the fuel rail was squared away and all of the injectors properly secured. I purchased a new battery, changed the oil, and put new fuel in the tank. And then I began trying to crank it up.
The electronics power on when the key is turned to on. When the ignition button is depressed, the fuel pump is heard for a second or two, and the starter begins turning the engine over. On my 2nd attempt the end of the hose that returns fuel from the fuel rail to the pressure regulator fissured a let out an alarming jet of fuel (at least I know the system is pressurizing, right?). I replaced the hoses, and kept trying. Essentially the bike sounds like it starts to fire up and then cuts off. I've pulled the fuel rail off and tested the fuel injectors to confirm that they actuate when you press the ignition button. I've also pulled the plugs and verified that they each have a healthy spark.
The air flow meter is new me, and I think my current concern is that there is some sensor or system that is, upon startup, sending signals that are effectively shutting the bike down.
I've also thoroughly cleaned the common ground that is found under the fuel tank.
There are probably a few other things that I've done to try and diagnose this, but which currently I don't recollect.
I welcome any thoughts or advice, and I can certainly answer any questions that might provide additional useful information.
Much thanks!