Hello everyone, I have a 2018 259d last eight of the serial number FTL14669. The problem that ive been trying to figure out is that the glow plug system is not activating the glow plugs, ive been trying to find a wiring diagram to help with diagnose, So far i have tested the glow plug relay and it is good, I also checked the 50 amp fuse and is good has power on both side of the fuse, it look a little crusty so i removed and clean all the connections even the 100 amp crank fuse while i was there, still no glow plugs. I then removed the 1 blue wire that goes directly to the glow plugs, had helper turn on the key while checking for power whit a test light it will light for 3 to 4 seconds then go out, when i reattached the blue wire back to the glow plug grid and retest again there is no power at all, remove the blue wire again disconnected from the glow plug grid retest it will light for a few seconds, I confirmed that the red wire from the fuse to the glow plug relay is good, the smaller orange wire sends power when the key is turned on, the small black wire test good for ground, the blue wire from the relay up to a 2 pin connector with a white wire I assumed the white wire is a ground I do not know for sure, but the blue has continuity all the way up to the glow plug grid, I'm struggling here i was trying to find a broken wire, but it seems to be ok in the engine bay, What controls the glow plugs the ECM???, Ive have read about the hydraulic temp sensor, and the engine temp sensor have something to do with how long the stay on, Also i removed the metal bridge that links the 4 glow plugs together, ohm each glow plug reads 0.8 all the same all 4, Any Help is greatly apricated
You do now. Check your message inbox. See Page 8 of the attachment for the theory of glow plug operation.
Relay sounds to not be carrying load or a broke wire one stran of the wire will light a test light but not carrry any amount of amperage.
Thank you very much for the wiring diagrams, and after reading the operation of the glow plug system with the temp scales, the machine is in my garage its 60 degrees the cool temp in the machine right now is 52 degrees, so according to that information would explain why we are not seeing a wait to start light, also want to let you know that this is a company owned they brought it in for a dead battery which i replaced with a cat one , did a 500 hr service on it, they complained about glow plug not coming on but it has not been cold enough, so is there really even and issue its been above 32 degrees F around here, the battery was 4 years old and weak, I wounder if the started got cooked from people cranking it with low voltage, last few months they were constantly killing the battery, and the starter isnt spinning fast enough say a 40 of 50 degrees, ohh dear your thoughts I used a halogen H4656 light bulb supplied power to the blue wire at the 2 pin connector put my own ground to the head light bulb and used the blue glow plug wire to active both the high and low beam to create a heavy amp draw and it stayed nice and bright both beams, and your thoughts as well thnaks guys
Are the glow plugs any good?
I tried to find a spec for resistance (or anything else relevant) for the glow plugs. No dice.
I find it easiest way to test the glow plugs, is to just take them out, one at a time and try them. They get hot, or they don’t. I have had them OHM quite low and still not work. I have also seen them scale up so bad, I either can’t get them out or they don’t produce much heat.
according to the mutilmeter they are, I will pull them and check the ol fashion way with my own power and ground, But reading the theory of operation that Nige sent me on how the glow plugs come on and for what length of time with temp of engine coolant, determining how long the wait to start light comes one for, According to the theory of operation at 50 degrees F the glow plugs will not activate, i have a some what heated shop its not cold enough in here, Right now this very moment the coolant temp and hydraulic temp in the machine is 50 degrees F, so the ECM says not cold enough for the glow plugs to be needed, all the wiring checks out to be good, feel like im on a wild goose chase with my shop not being cold enough,
Ill pull the glow plugs and check the ol fashion way, But the theory of operation of how the glow plugs work with the temp and duration of how long or at all if the glow plugs should be on for, Right now this very moment the machine coolant and hydraulic temps are 50 degrees F in my shop, According to the operation of theory the glow plugs will not activate because its to warm in here, the wiring seems to be good, im runnig outta ideas oh boy.....
im going to check em the ol fashion way, but according to the theory of operation of the glow plugs with the current temps of the machine being 50 degrees F the ECM will not activate the glow plugs because its to warm, customer stated the glow plugs to not be working maybe ill put it all back together and put it outside were its a chilly 25 degrees F out the and test, Running outta ideas... Help S.o.S
Yep maybe a case of tgere not workomg because we dont know how they work
Agreed im hoping that the information that Nige sent reading the operation theory on this 3.3 engine is accurate, ohh dear anyway enough for one day ill keep on struggling after the New Year, Happy New Year Everyone Thansk for the help,
Maybe @Nige can find it (I no longer have SIS privileges) but I vaguely remember there being a software update a few years ago pertaining to the cold start strategy on Cat skid steers. If my memory is correct it had something to do with the glow plugs. I guess the other thought I had was what is the machine seeing for ambient temperature?
I’ll have to look that up but it won’t be today…. Or maybe it will....... See SEPD1785, but by Serial Number that upgrade should have been installed on FTL14669 when it was built. However M0101157-04 does seem to apply. It affects machines up to FTL17324. I've highlighted the relevant parts.
I have a minature clamp meter with tiny jaws ( Extech 380947 ) that I have someone climb in and go to start while I clamp the cable feeding the grid heater or glow plugs. Know instantly how much is feeding or if none is. As Niges post #2 explains , don't expect any power to glow plugs if too warm. I have had operators before that claimed it use to work every day same temperature, was all their confusion and only that. System worked flawlessly when correct temperature. Told management the operator was nuts. Simon C
Where they having trouble starting machine, to begin with? At 50f it should start without heat. Does it? Cold start monitor boot up takes 8 seconds. Any pre heat less than that, will not illuminate cold start, according to theory of op. Maybe that's what they are basing their claim on, that its not working. All the years I've worked on machines, I always regard what the customer thinks is wrong, as suspect, and try not to let it lead me down a rabbit hole.
Yes M0101157-04 was the one I was referencing. I remember updating a lot of skid steers for that one since we're considered a cold climate.
I have found when working with my service techs to just tell them what the machine is doing(or not doing) and leave the guess work to them, I no longer say this is what I think the problem is