Cat 416c. Had an issue with dash lights turning themselves on while keyswitch was in off position, or when it was running all dashlights would come on, randomly. Keyswitch was old and very sloppy, replaced with new switch from Cat. Problem solved. For one month. Last night i was in shop and heard a machine start so i went outside and 416C had started itself, no key in ignition, and in off position. Despite running dashlights were all on. I put in key, turned on and shut off, it turned off fine. Went back inside and about half hour later machine starts itself again, again with no key in ignition. This time it kept randomly engaging the starter, grinding it against flywheel. Shut off with key again, but kept trying to start itself, and keyswitch was very hot to touch. Disconnected batteries. Anyone have any ideas, outside of the obvious, which would be a defective key switch. I find that unlikely, although possible. Is there another solenoid other than starter that could be backfeeding keyswitch? Other thoughts?
Mice chewed up a wiring harness? If you can't find any obvious damage visible, then it might not be that hard to replicate by bending the wiring harness, wiggling connections, tapping the key switch, etc. Do this with the battery hooked up, but loose to remove it quickly, a hose nearby is not a bad idea either.
Sounds like you have a short in the wiring harness
It’s a ghost. Only sensible explanation.
worked through the whole wiring harness with an ohm meter looking for shorts. did not find any. reattached batteries and went through harness bending, looking for shorts, etc. machine continued to randomly start itself, and, once started, starter would attempt to engage. keyswitch continued getting very hot. narrowed it down to one wire on the relay circuit, yellow wire. would get very hot with key just in RUN position, not running. very hot, hand burning hot, and always at keysitch connection. replaced keyswitch with new one i had in stock. wire continued to get very hot. removed all relays from machine, wire remained hot. traced that wire to injector pump fuel on/off solenoid. removed wire and keyswitch cooled right down. connectors at fuel pump are slip on spade connectors, wire appeared to be barely on, perhaps backed of due to vibration, although it certainly did not affect running. i pushed wire down solidly on spade, connection at key switch cooled off. my working theory at this point is one of 3 things, will spend more time on this tomorrow but got darked out. 1.first thought is that spade connector was loose, and was thusly drawing way more amps than it should. this eventually overheated keyswitch to point where it warped connectors inside, causing random start situation as temps cooled and exacerbated warpage. 2. second thought, perhaps in moving spade fitting i moved wire enough that bare wire somewhere was no longer in contact with chassis and thus no longer grounding, although it could not be grounding too much as it was still sufficient to power inj pump solenoid. but a short could cause same scenario in keyswitch as above. however, could find no bare spots, harness is in exceptional condition w/ no mouse dmg etc. 3. in the process of pushing spade fitting down i moved something inside solenoid that was shorting out, this one seems highly unlikely to me. i would entertain all other theories.
Welcome to HEF, James ! Be suspicious of the IP shut-off solenoid.
what are you basing that on, your experience or mine?
Theory #2 sounds plausible. I’m with Tinkerer on maybe the IP solenoid is drawing too many amps. Sounds like you know your way around a dvom. Test it. The resis No, I don’t have the exact spec handy. But, the resistance of the coil should be 3.5 to 4 ohms. So, 14.6 volts divided by 4 ohms, should give you a amp draw of 3.5 amps. Not enough to burn up a ignition switch unless there is a short to ground somewhere on that circuit. I’m kinda curious why it didn’t toast a fuse. Maybe it is a ghost. IDK?
Ghosts don't cause shorts Coaldust, that'd be a gremlin, deal with them rotten little ba$tards all the time.....Sorry Jim
Do you need the electrical schematic diagram ? Even if you don't I will post for anyone that may searching for it in the future. It has to be enlarged quite bit to be readable.
Is the cold advance solenoid or the shut-off solenoid getting hot ? Couple thoughts about the gremlin starts. Follow the 304 starter s terminal wire to the start relay. Along the way, 304 shares a connector with adjacent hot-all- time 101 at connector 39. Maybe that connector is full of green goo corrosion? Maybe a short to power? I would test the starter relay, too.
thanks for all the answers, just got back to computer after a few days getting caught up. went over entire harness again, it is in remarkably good shape, i really expected to find some mouse chewings or some corrosion, but in the end i found ....nothing. i did put in new battery cables with cole hersee 75908 shut off switch, which i generally install on my machines anyway. i was suspecting the new keyswitch to be faulty, but then replaced it and that one started to overheat also. in the end the only thing i could find out of line was a loose spade terminal on the injector pump fuel solenoid. with it on firmly i have had no problems, but given the randomness of the whole thing the batteries get shut off when not in use. i did check all relays. for me the confirming factor was that when i fully detached wire from solenoid it stopped getting hot, and when placed on firmly, it stopped getting hot. i think that caused the keyswitch to melt down while running, and warped contacts enough to random start while off. but again, there is always the possibility that i moved something inside solenoid whilst pushing on. thanks for all the thoughts on it. and i did have the schematic, but thanks. at this point i am thankful i was there to witness the random starting, and wasn't made aware of it by fire engines going by.
I had this happen to a 416b backhoe, It started after I briefly welded on the door. The backhoe would just randomly start up all by its self. I unfortunately didn't fix the problem correctly and ruined the starter.
and what do you think the welding caused? what did you find to be the issue? did a new starter solve the problem? i really don't understand how, if the machine is not running, welding could cause any problem on a machine without an ECM. i have welded on dozens and dozens of older machines and never seen or caused any issues. why do you think there is causation?
ok Last night I couldn't remember what it was that we fixed but I asked my mechanic this morning and He couldn't remember for sure if it was a rely or a solenoid that went funny on it. I'm not sure what welding had to do with messing them up but thats when the backhoe started to to start on its own. so if I weld on my machines now I prefer to disconnect the batteries.
What about the starter itself, could you disconnect the solenoid on the starter and see what happens.
You should always disconnect the batteries when welding. Any vehicle with electronics is especially susceptible to damage from a welder.