Hello, I have a 2015 Cat 308 S/N FJX02738 that developed a bad parasitic draw which was killing the battery pretty quickly, and was needing a jump to start each time. I swapped out the old battery with a new one as I could no longer start the machine with the old battery even when jumping. The draw problem had been going on for about 2 months and killed the battery. When reconfirming the parasitic draw value with the new battery, I heard a pop or click, I thought it was either a fuse popping or a relay clicking it was hard to tell but the draw went to 0. Now the machine will crank, dash lights up, but will not start. I went through all of the fuses and relays that I could find and here is where I am at: 1. No fuses or relays in the attached pictures are blown, they are all intact an function correctly. This includes those inside the cab and the fuses and relay located next to the battery 2. On the in-cab fuse panel, with key on, there is 12v power to the ignition, cab screen/radio, horn, 30a computer (guessing on the symbol), joysticks (10a and relay), beacon/strobe light, and what looks like an engine timer or hour meter relay. Everything else has no power with the key on, including the ECM relay. See picture marked with power/no power 3. I connected a diagnostic tool to the 9 pin connector, it powered on but could not communicate with the ecm 4. I confirmed the fuses by the battery (see picture) are intact 5. The relay by the battery which is part of the ignition circuit is working. I swapped it out with a new relay just to be sure and nothing changed 6. The 12v fuel pump by the fuel tank gets no power with the key on, likely due to the ecm getting no power I would think From here my questions are: 1. Are there other fuses/relays I should check other than those pictured? I found a diagram on the Cat central app that shows additional relays related to the fuel pump but I cannot find them. 2. I have not checked for power, key on or off, at the fuse terminal by the battery, is that worth checking? Again they are all intact when doing a continuity test 3. If no other fuses/relays to check, what do I do next? Thanks all
Sounds as though you do not have an electrical schematic. Would you like one.?
Yes please!
Check your message inbox. Kudos for posting the Serial Number by the way, because there are three different versions of the document depending on the Serial Number.
In the picture of the fuse box you have a note that says 86 and 30 both have power. That is good but, 86 has to go through 85 and back to ground or no relay switching. Also pin 30 goes to 87 then must have a good path to wherever the schematic shows it feeds power to. I don't have the schematic, but Nige sent it to you. Best check on these items before firing the parts cannon. Simon C
You do now.
Was looking at the fuses below the seat. The fuel priming pump is powered by a 10 amp Travel Alarm/Fuel pump fuse. Need to verify if the fuse is okay and check all the fuses with a load if possible like a test light. Is there the possiblity that the glow plugs are not working also, cause you stated the engine cranks but don't start. No power to ECM Relay I will have to check on. Simon C
There is 3 relays next to the battery. The Engine glow plug relay is number 1, and powers the Engine Relay Power 3. They are all side by side and if one fails the other will not go from what I figured out. Pull those relays out and make them run a 10 amp lamp remotely. If they fail, garbage can. Need to prove they don't fail under load. The Engine Relay Power3 is fed by the Computer Engine ECM Relay Coil output . I think I have it correct. Maybe someone else will correct me. Simon C
I appreciate your interest in my problem, I have solved it. First, thank you to Nige for the schematic, I figured out this issue in about an hour with it in hand and would not have without it. There are some errors in my original post as I had googled some of the symbols on the fuse panel and got bad info. I apologize for my lack of electrical knowledge and terminology, but there is an "always on" 12v wire to the ECM, which was on, and a "key on" wire that was NOT on. The schematic helped me determine very quickly that the issue was somewhere in the "key on" circuit as all of the fuses not getting power only get power with the key on, and the fuses/relays that had power were those that have it all the time. I was able to follow the wire group 308 (the number happens to be the same as the machine model) from the ignition back to the main power relay that is next to the battery. Simon, you were correct this was the place to investigate. This is embarrassing but I had created my own problem, when I was checking the fuses at glow plug relay, the main power relay and engine power relay (the three next the battery) I switched the plugs for the main power relay and glow plug relay. I could not get the fuses out without removing the plugs. When I switched them it started up just fine. Which was great because the machine got put on a water main job yesterday! I have a small company and my 308 is definitely the most important machine that I have. There was some stress/panic when I was doing the initial diagnostics without a schematic and I'm very glad I was able to get it sorted out. Thank you again for your interest and help with this.
What about the original problem with the parasitic draw. Was the old battery just bad?
It is not there anymore. The battery that went bad was less than 2 months old. I measured a ~300 milliamp parasitic draw but that was on the old battery after it had been charged/jumped many times. The machine had just returned from the dealer for service when the draw started happening and a number of my employees use the machine. I am thinking that something was left on and no one realized it, myself included, and when I was going through the machine last week I switched something off without really thinking about it.