So I seem to be having an issue with glow plugs activating on my machine. Initially I tested for 12v at the glow plugs and had nothing. I checked the fuse and it’s good, and when I jump the relay the glow plugs get power as well. I’m noticing my trigger wire for the glow plugs relay is only showing 9v which makes me think it’s not enough to trigger the relay. Manually wiring the relay and putting 12v to it triggers the relay as it should, so the issue is the trigger wire (orange). Any thoughts? Thank you
Got a Serial Number.? That gets you the electrical schematic.
EDTB03529 Appreciate the help
Check your message inbox. Wire F793-OR comes from the Engine ECM connector J1 Pin 24, marked "INTAKE HEATER RELAY COIL +(POS)". Between that point and the Glow Plug relay it passes through one major harness connector, marked CONN 28. I would start by backprobing the Engine ECM connector J1 and check the voltage at that point.
Got a Serial Number.? That gets you the electrical schematic. As Nige has sent you the schematic, I had a look at it also. Not going to highjack the thread Nige but wanted to figure it out for myself. Might be wrong, but from my search Engine ECM 436-0821 has plug J1 with 80 pins. Pin #24 is the Intake Heater Relay Coil Positive feed. This wire will power up the glow plug relay. Would backprobe that wire F793-EJ11 OR-18 with the red test lead of your meter and touch your black test lead to the center of the negative battery terminal while turning the glow plugs on. Should have close to full battery voltage, like 12 plus volts. Then move your Black test lead to the glow plug relay orange trigger wire and activate the glow plugs again while watching your meter. Should probably be a reading maybe around 0.5 volts maximum less than the previous test. If you are loosing like 1-3 volts from the original output at computer, you probably have a bad connection in between. If I have missed some Nige, all ears to your experience. Simon C
Sorry Nige, did not look up to see you already posted. Hard to keep up to you. Simon C
Simon and Nige, appreciate all your help this far. So with a second set of hands I was able to determine that the relay does get 12v and the glow plugs do turn on when the indicator shows but only for a split second. Is there a way to change the temperature settings to cycle them longer or for them to come on at higher temps than they’re set to? For reference the machine was at about 37-40*F ambient temp today. The relay trigger had 12v when the key was first turned and the indicator came on the deluxe screen, but it wasnt nearly enough time for the glow plugs to activate and get warm. Machine did start fairly easily without them but it's when the temp is lower that I have an issue. Any input would be greatly appreciated.
Something is wrong in that case. The operation of the glow plugs is controlled 100% by the coolant temperature switch. That should be your next port of call. Is the switch working.?
Do you know the temp the glow plugs should activate at? And for how long? If imagine the time varies based on temp. I will investigate the coolant temp switch to see what it’s reading compared to the actual temp.
See the text & illustrations below. When the key is turned to "ACC On", the lamp and the glow plugs are activated per the time and temperature strategies listed in the Illustration. Once the machine is started, the glow plugs will remain on according to the strategies shown. All durations are dictated by coolant temperature shown. (A) Pre glow (glow relay ON) duration (B) Afterglow (glow relay ON (C) Water temperature (Celsius) (D) Water temperature (Fahrenheit) (E) Time (seconds) Note: Monitor boot up may take up to 8 seconds. Any pre-heat less than 8 seconds will not illuminate the cold start aid light.
This is a huge help, thank you. Let me investigate the water temp sensor and take it from there. Could this also be something that was addressed with software update? Or unlikely
Not AFAIK, but I've been wrong before......... I certainly can't see any service publication announcing any sort of changed glow plug strategy.
So right now I have the machine inside to service it (machine is new to me) and the coolant temp was above the threshold where the glow plugs would kick on pre start. I do notice a voltage drop when it first starts for 10 seconds or so which coincides with your diagram above regarding glow plug timing. Once I figure out my other issue (listed below) I’m going to leave it outside to test the glow plug circuit once again. Performing service on the machine (all new filters oil change coolant flush etc) I believe I may have found the culprit for the hard start. I changed the fuel filters and they wouldn’t prime. Check the pump fuse and it’s blown. Replace it and it fills up the main filter and the pre filter halfway. And then it blew the fuse again after I cycled it a couple times. Now it blows it instantly when I turn the key on. So it seems like I may have a restriction in the tank. I believe I saw a fuel drain near the inspection plate so I plan to drain the fuel tank and perphaps blow the line clean from the tank to the pre filter/pump. In your experience can that transfer pump being bad cause a long crank?
It appears that you may be suffering from a very common issue known as "contaminated fuel system syndrome". Quite simply people don't take care to use clean containers when refuelling and contamination gets everywhere. You are right to start with the tank. After that blow all the lines through to the inline screen just below the priming pump. Then replace the screen (see attachment - P/N is on it). It's not worth trying to clean it. Then move to the fuel filter assembly. Remove the complete assembly from the machine and disassemble it. Remove all the fittings. Blow through each fitting and the passages in the head of the fuel filter assembly using compressed air to ensure that they are clear. Ensure that the check valve is working correctly and is not stuck. Then put everything back together and see how it goes. What you should be aware of is that the priming pump ONLY runs for a limited time when the key is turned to the ON position simply to fill the fuel filters after a filter change. The HP fuel pump on the engine contains an internal transfer pump which is responsible for sucking fuel from the tank through the filter to supply the injection system while the engine is running. Seeing as this machine is new to you I assume that the Operation & Maintenance Manual that normally lives in the pocket behind the seat is AWOL.? If it is then you need to get hold of a replacement. SEBU9084 is the publication reference and here is a link to one on eBay
Nige is onto it. Only thing I will add is that your transfer pump is probably toast. They don't like bad fuel. The fuel pickup at the bottom of the tank is easy to remove also. This allows you to suck out any crud/water sitting on the bottom of the tank. If hard starting continues after that please report back and we'll try a few other things.
One thing I failed to mention in Post #14 above, that "contaminated fuel system syndrome" could easily cost you an HP fuel pump, a fuel rail, a set of injectors, and all the associated hardware, etc, that is necessary when they are replaced. For all the aforementioned items you probably won't get change out of $6k+. Should focus the mind wonderfully........
New small electric pump on order. At this point it keeps popping fuses and is completely dead when I put 12v to it. I drained all the fuel today and the tank was actually pretty clean, much less sediment than I expected so I’m optimistic, it seems like whatever was in there was caught by the prefilter. Despite the filter being new I am going to purchase another new one anyway. I also noticed whoever installed the old large fuel filter put the oring in the front spot, so it’s likely it was sucking in some air until it primed. Had to be sealed somewhat decently as it didn’t leak at all, but I’m sure it did not help.
I did find the manual today, I wasn’t even aware of the small pump not working until I had to prime the filters. Luckily the machine hasn’t seen much use and runs perfect once it’s starts so I’m optimistic. It’s a low hour machine, spent more to avoid these issues and here we are ha! Luckily it didn’t go straight to the job site I was doing service on it first so I’m hoping no damage has occurred. Machine runs perfect besides a longer crank on cold starts.
@04yfz Did you solve your glow plug issue?
Where in SIS did you find that start aid chart (post#10). We now have SIS, and not being familiar with it, I am having a heck of a time finding that chart. Thanks for posting it. It is a help for me and the machine I am working on.
Nige has a lot of secret weapons in his archives. LOL Simon C
I wish I could remember where I foun dit, but unfortunately I have slept since then..........
Depending on the glow plugs not all are 12 volt. The NGK glow plugs on my skid steer are rated at 10.5 volts. There is a resistor/glow indicator that lowers the voltage. My machine was hard to start and turned out 1 glow plug was bad. I think at least 1 more was getting weak. New glow plugs and all is well.