I thought I would just bypass this starter relay switch. There is a wire (yellow arrow) that goes inside the starter. Does anyone know what this wire does. I put 12v to the solenoid and the starter engaged but it will not stop. I thought maybe it was a fluke so I disconnected ant wires to that terminal on the solenoid and tried again still keeps the starter engaged when voltage is removed from that terminal.
I'm trying to understand why you are attempting to bypass the starter relay switch (magnetic switch). The switch is there to carry the high load current from the battery directly to the starter. Before we go any further, some extra information may help. 1. What is the S/No of the tractor? There are multiple wiring setups/diagrams for the D3, depending on the S/No. 2. What is the make/model of starter? Nippon Denso or Delco Remy? Do you have a P/No for the starter? 3. Is the engine a precombustion chamber engine or direct injection engine? Does it use glow plugs? 4. Have you changed the engine from the original? (i.e. - gone from PC to DI or vice-versa?) The starter looks like a ND starter to me, and it's difficult to source a wiring diagram for the ND starters. Delco-Remy have a good supply of technical information, but the wiring setups for ND starter are vastly different to the D-R starters.
To me the magnetic switch is redundancy. It doesn’t carry heavy load it sends the voltage to the terminal that would normally be going to the starter button. As I said I hooked the starter button to that terminal but the starter stays engaged. So I removed the wire from that post and jumped it same result the starter comes on as expected but doesn’t cut off. The solenoid is pretty much like a Chevrolet solenoid in how it works. Why the wire at the yellow arrow is there and what does it do is my question. If I can’t do this way I’ll just switch it back
The magnetic switch nuts on the picture look kind of rusty. Possibly the wire with the yellow arrow pointed at it is a ground wire for the magnetic switch. That rubber boot over everything needs to come off to clean up all the connections and see who is who. Have seen magnetic switches like you have with welded contacts before. Not 100 percent on what you have. Need a schematic as OzDozer said. Simon C
That is the Delco Integrated Magnetic Switch, or IMS it prevents the key switch from engaging the starter when the engine is running. It’s not necessary, but it’s a nice feature. You can go to the Delco website and see a wiring diagram. I’ll try to post a link. It may not be a perfect match, but it will give you an idea. The wiring is mostly the same. Or, cross reference your Cat starter number to the Delco number. Looks like a 30MT? https://www.delcoremy.com/documents...-magnetic-switch-(ims)-(relay)-installat.aspx
That’s not mine it’s just a pic I grabbed to show the magnetic switch. It is the same setup as mine though.
Okay. Thanks for clarifying that. They are all wired the same, 99% of the time. But, it might be a Nippon, like Mr. OzDozer said. I can’t tell. But, please consider not bypassing it. Especially, if other people run it.
#2 wire goes to the terminal on the solenoid that engages the starter, as you would when you turn the key or push the button. #4 goes to the battery terminal on the solenoid. This powers this relay. #5 I haven’t figured out what it does. This may be the safety wire. The second from the top unnumbered wire goes to that post with the yellow arrow. I was hoping one of you had been down this road and could tell me what that terminal does. I’ll hook it back up tomorrow and see if that has anything to do with the starter staying engaged after I let go of the button. The starter was working great I just took the end off of the solenoid and dressed up the copper contact because it wasn’t making a good connection and you would have to bump the starter button to get it to engage.
#5 should go to the ground on the solenoid. That is an ND. What’s that other wire doing? Hmmmm. Let’s grab a wiring diagram.
Nige has worked with me on figuring out the serial number. It’s around 24y1500-1700.
Sure looks like a ND starter to me. Under the plastic cover is a copper strip that sometimes can be flipped around to get better contacts. Maybe it isn't needed if you want to jump start at the starter. One of the wires is also a fusible link. I found that out by fluke when the starter button wouldn't work.
Having a difficult time locating that diagram. I think it’s the key switch wire just like you said.
Keep an eye on your messages for an incoming schematic. It's not the greatest as regards clarity but it's all that exists.
Curious if a 931B might for some reason have a better schematic, 25Y or 29Y.
I believe the wire your inquiring about is the starter field connection
This diagram of the switch and solenoid looks like a stick people family tree to me. Maybe when I’m look8ng at the starter it’ll make more sense. I have seen some mention that the wire in question energizes the other end of the field. Don’t know what that means.
O.K. Your tractor S/No indicates a 1983/84 year of build. All the D3's and 931's were built in Japan, anyway - so they used the Nippon Denso starter as original fit. Many D3/931 tractors still seem to have the original starter, and it appears your starter is original. The D-R equivalent to this ND is a 37MT - but we're dealing with an ND here, so we can forget the D-R. The starter part numbers bounced all over the place as Cat went through about 6 changes of starter motor P/No. in the D3's and 931's/3204's. Regardless, they are all either F4 or F8 ND starters if they came from Japan. I have worked on the 4N-0241 starter P/No, which appears to be common to many of the D3's and 931's. The P/No number was upgraded later to 3E1865. The ND starter P/No is 028000-5961. You will find other (interchangeable) P/No's, both Cat and ND, but these ones are the common fit. A number of the starter P/No's are now obsolete. ND regard this starter as obsolete, they want you to buy the latest design planetary reduction gear (PGR) starter motor, and scrap this one. The PGR starters are better, but hey, we're working with what you got. I've uploaded a file that is the ND F4/F8 wiring diagram/disassembly/assembly. The problem you have encountered has been previously discovered - and here is the explanation .... "Owners have reported (D3/931 - 3204) starters that remain engaged after the engine is running. The problem is likely to be caused by an open shunt field winding. The shunt field winding is inside of two opposite field coils. Damage to the shunt field winding is caused by starter motors that have been overheated from extended periods of cranking, or by faulty (sticking) start switches. If the shunt field winding is open, the magnetic switch (starter solenoid) will not drop out. Use a Cat 6V3030, 6V7070, or 6V7800 multimeter to test the shunt field winding. Touch the negative test probe to the starter motor case and the positive test probe to the shunt field winding terminal. The correct resistance for the shunt field winding should be 0.6 or 0.7 ohms. If the shunt field winding is open, replace the field coils with a 4N7553 Field Kit."
Thank you Mr. OZ! That’s exactly what I was looking for. I don’t think my starter is bad, at least it wasn’t before my experiment. I think it sees the open shunt because wire 15, the shunt wire, is not hooked up. I’ll hook it up and report back. I had flipped the studs and refinished the copper strap in the solenoid for a new surface and thought maybe somehow with it being new it was welding together. But when I disconnected power it reset and did what it thought it was supposed to do. Many many thanks!
I read the disassembly instructions over and over (instead of wasting my time sleeping). It says remove the relay and talks about the shunt wire (15) and terminal 51. It never mentions the other end of wire 15. That wire is still present after the relay switch is removed. So I keep researching. Then I find solenoids for sale and low and behold they have wire 15 on them. Mine isn’t that way either using that wire from the relay or having been modified in the past. I’ve had 2 fires on this dozer while I’ve had it luckily being able to extinguish them before they became fatal. So some of the wiring is burned while other has just been abused over the years. So I’m going to give it one more try sans the relay but adding back in wire 15. I’m aware most of you if not all would say just leave the relay but I think it’s redundancy having it and the solenoid. This doubles my chances of having a relay issue on the starter. So I’ll give it a test with the added wire and if that’s not successful I’ll add the relay back in entirely. I have the new engine mounted and just about ready to fire. I do not have the nose and radiator on yet. I want to just fire the engine before I finish up the assembly. The previous owner of the engine attempted to rebuild it and stopped when they couldn’t get oil pressure.I found the end plugs missing from the oil galley. I think this was his problem. Before I hit the starter it crossed my mind what happens if the starter hangs on or the engine fires. I said one I don’t have fuel to it so it can’t start and two the starter isn’t going to hang up. I didn’t have the oil level full but I had primed it twice just to make sure I have everything prelubed good. On my second attempt on the starter I checked the oil level it wasn’t enough to register on the stick. So I hit the starter again and watched the oil pressure gauge. I had 50 lbs while the starter was stuck. Man am I glad I used the preluber first.
Some start systems may use a relay from the start switch to the starter solenoid because the start switch alone may not be able to handle the required current that the solenoid needs, especially in 24v start systems or even in heavy-draw 12v systems
Dodged a bullet on this. I hooked the wire from the solenoid terminal to the shunt terminal. All is well now. Luckily I didn’t fry the starter with my little experiment. I don’t understand why you have to wire it this way as that starter terminal only sees voltage when the button is pressed. When it’s released it sees no power. Something has to back feed through the windings to energize the solenoid and keep it engaged. Thanks all for your help.
Within the main solenoid is a pull in and hold in contacts and coil. The auxiliary solenoid pulls in the shunt circuit. These functions only work while in the start switch activation mode.