Hello folks, I have an early Cat 315L that suddenly no longer started when I turned the ignition. Here are the details surrounding the situation, hopefully, there are some clues for you experts that may point me in the right direction. I was working on removing the hydraulic cylinder for my thumb (it had been leaking and needs a rebuild). I set my bucket on my trailer to make it easy to drop the cylinder on the trailer after removing it. I turned off the excavator while removing the hydraulic lines and pins from the cylinder. Once completed, I went back to start the machine to move the bucket off the trailer. The panel came up, the alarm started beeping, I could hear relays and pumps, but when turning the ignition to the end, there was no starting of the engine--it was silent! What I did next may have caused more damage than good. The ignition switch was 'wonky' since I purchased the machine (used), the key did not go in well and it stuck on occasion. I thought, perhaps the ignition switch finally went out completely. I opened the panel to look at it (I did not realize the switch is completely enclosed) and while doing so, I set it down. Not having disconnected the batteries or turned off the power switch (which is frozen closed) BEFORE I started tinkering, I saw some sparks when the ignition switch was set down. I immediately tested the switch again and not only did the not machine start, but it was also now completely dead. No panel, lights, alarms, or any sound occurred--very dead now. So, I suspect I have two problems. The first is to restore some basic power, and the second is to have the machine start. I did check the fuses in the panel but did not see any of them blown. One of my questions is around the removal of hydraulic lines--does the drop of pressure in the system cause it to eliminate starting? Is there a safety cut-off for that purpose? I thought was quite a coincidence that starting problems and the removal of the hydraulic lines occurred at the same time. Thanks for your help!
hi, As i know there is no such thing related to starting circuit. Double check whether all the fuses are good. specially fuses for Key switch, monitor and controller(ecu). Check whether B+ voltage is available at the key switch and controller fuses . There should be battery + voltage at least at one side of these two fuses. if the fuses are good then this voltage should present at both sides of the fuses. if voltage is present at this fuses correctly then check whether battery voltage is available at the main relay( between red & purple wires) and check whether is it working properly. check whether key switch signal ( battery voltage ) presents at the two small wires (between yellow & black wires) at the main relay when you turn on the key switch.
Anuradha, thanks for reaching out with suggestions. I will be onsite with the machine next week and will take my multimeter with me to start tracing the voltage back to where you identified that I should look. I will also have a fresh set of fuses for replacement, just in case I missed a blown one on the first inspection. Thank you.
I sent you a copy of the electrical schematic. You may find it useful.
Folks, thanks for the response from the forum. I used the electrical schematic that I downloaded to my iPad to use onsite while I'm working on the machine. With it, I was able to follow the current flow (or lack thereof) to the starter. I finally narrowed it down to a faulty start relay which led me to replace the entire starter assembly while I was at it (rebuilt from Cat, no Chinese replacement). In addition, I found that the (yellow wire) ground wire from the safety switch was not closing correctly--I saw that the previous owner has put a ground wire bridge to the start relay. With that in place, the machine started. I do notice that it does not want to shut off at low RPM, but will shut down from at higher RPM--not sure what is going on there. Nonetheless, it is good to hear the engine run again. I want to communicate that people that have these older machines should purchase a parts book. I found an original in good condition from eBay. It allowed me to identify the parts I needed quickly and order them directly from the Cat parts website, upon which they were waiting at my local dealer after two days. Cat service is great and the prices on rebuilt parts (when you hand in your core) are fair and well worth the extra cost over Chinese copies.
Cat allows parts book access for no charge if you have a store account. I find "avspare" extremely useful too, both for parts and service. It's not complete on service side, and somewhat counter intuitive to use, but it has been extremely helpful.