Kabota L 3901 Help
- Thread starter G.R.D.
- Start date
Back up a bit, first, and review how a relay works. It's just a switch operated by a small electromagnet. You'll have two terminals which connect to the switch, and two which connect to the electromagnet. (Often you'll have 5 terminals. Don't worry about that unless all 5 are connected. Often it's just 4, and that should be the case here.)
Let's see if I can post a diagram from The Twelve Volt .com (an excellent resource!)
When we provide 12v to the electromagnet, it pulls the switch over (against a spring) and connects the two switched terminals. That's all - it just connects the other two terminals.
So, we give 12v to one side of the electromagnet, and we give 12v to one of the switch terminals. Good so far?
Then we connect the other side of the switch terminal to the fuel pump. Now, if we ground the last terminal, the other side of the electromagnet, we get current through the magnet, which pulls in the switch, which connects the 12v to the fuel pump, and it runs and squirts diesel into your eye because you were looking into the output hose to see if anything would come out. That was dumb!
So, if everything is workign correctly, if we ground that last terminal, we should get power to the fuel pump (and some other things). OR, if the ECU connects that terminal to ground, we should get power to the fuel pump (and some other things).
Now, find the relay. Using your multimeter, find two pins which have power when the key is on. According to that diagram, two pins should be hot when the key is on. Note which two pins they are. We'll call these Pin 1 and Pin 2. (Kind of like Thing 1 and Thing 2, but without the Cat.)
Now, check the other two pins. There should be no voltage present on either one. One of them is likely a smaller wire than the other. (I'm expecting two larger and two smaller wires connected to that relay. Probably.) Let's call them Pin 3 (big) and Pin 4 (not so big).
The smaller one, Pin 4, is probably where you can find the ground signal from the ECU. (The larger one should be the output to the fuel pump.)
To test it, connect your multimeter hot lead (red) to 12v somewhere (anywhere), and then to the ECU ground pin, Pin 4. You should NOT see any voltage. Now, with your meter still connected, turn the key on and try to start. You should see 12v now. If so, this proves that the ECU is sending the correct ground signal to the relay. If not, you either have the wrong terminal or the ECU is not sending the ground signal.
To test the relay, simply ground that terminal and see if 12v appears on the 4th terminal. It should, if the relay is working. (You should hear it click.) That should get you fuel. If not, the relay is probably the problem.
(In all of this, if you are not taking detailed notes AS YOU GO, you are shooting yourself in the foot, You CANNOT remember it all. You WILL confuse yourself.)
Let's see if I can post a diagram from The Twelve Volt .com (an excellent resource!)
When we provide 12v to the electromagnet, it pulls the switch over (against a spring) and connects the two switched terminals. That's all - it just connects the other two terminals.
So, we give 12v to one side of the electromagnet, and we give 12v to one of the switch terminals. Good so far?
Then we connect the other side of the switch terminal to the fuel pump. Now, if we ground the last terminal, the other side of the electromagnet, we get current through the magnet, which pulls in the switch, which connects the 12v to the fuel pump, and it runs and squirts diesel into your eye because you were looking into the output hose to see if anything would come out. That was dumb!
So, if everything is workign correctly, if we ground that last terminal, we should get power to the fuel pump (and some other things). OR, if the ECU connects that terminal to ground, we should get power to the fuel pump (and some other things).
Now, find the relay. Using your multimeter, find two pins which have power when the key is on. According to that diagram, two pins should be hot when the key is on. Note which two pins they are. We'll call these Pin 1 and Pin 2. (Kind of like Thing 1 and Thing 2, but without the Cat.)
Now, check the other two pins. There should be no voltage present on either one. One of them is likely a smaller wire than the other. (I'm expecting two larger and two smaller wires connected to that relay. Probably.) Let's call them Pin 3 (big) and Pin 4 (not so big).
The smaller one, Pin 4, is probably where you can find the ground signal from the ECU. (The larger one should be the output to the fuel pump.)
To test it, connect your multimeter hot lead (red) to 12v somewhere (anywhere), and then to the ECU ground pin, Pin 4. You should NOT see any voltage. Now, with your meter still connected, turn the key on and try to start. You should see 12v now. If so, this proves that the ECU is sending the correct ground signal to the relay. If not, you either have the wrong terminal or the ECU is not sending the ground signal.
To test the relay, simply ground that terminal and see if 12v appears on the 4th terminal. It should, if the relay is working. (You should hear it click.) That should get you fuel. If not, the relay is probably the problem.
(In all of this, if you are not taking detailed notes AS YOU GO, you are shooting yourself in the foot, You CANNOT remember it all. You WILL confuse yourself.)
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Another poster said you don't have a fuel shutoff solenoid. If you jump the fuel pump you should get fuel, but if the ECU is not happy, you still won't start because it won't fire the injectors.
Check to see if the relay is okay (my post above) and if the ECU is providing ground to the relay.
Once we know that, we can go from there.
you do not have a fuel shutoff solenoid so forget about trying to mess with it. You can't mess with it if you don't have one!
Your tractor's engine is controlled electronically, like almost all new cars
it shuts the engine off by removing power from the injunktors I mean injectors, high side pump, all the sensors, and scv. The low pump will continue to run up to 30 seconds or so after you cut the engine off with the key. This is normal. It is to cool the injectors among other things. it still pumps fuel through the injectors to cool them but the injectors are not firing. The injectors are electronic and not mechanical.
because it's electronic you don't really need to be "jumping" anything. In doing so, it'd be real easy to fry the ecu via backfeed. And ecu's are not cheap, easy to get, or fun to replace.
ideally you need a wiring diagram and also need access to the hardware and software that will connect to the tractor's ecu, so it can be read and then you can figure out what ain't doing what. But since you don't have that, you have several choices. Throw parts at it. Hire a certified shade-tree mechanic. Fiddle around with it using certified youtube mechanic's guiding, or take it to a dealer and let them figure it out. Option #1 and #2 could very easily cost you a few thousand dollars. Option 4 could too...or they could have it figured out in about 10 minutes...never know.
I didn't read all the replies. Did ya check the fuses?
Your tractor's engine is controlled electronically, like almost all new cars
it shuts the engine off by removing power from the injunktors I mean injectors, high side pump, all the sensors, and scv. The low pump will continue to run up to 30 seconds or so after you cut the engine off with the key. This is normal. It is to cool the injectors among other things. it still pumps fuel through the injectors to cool them but the injectors are not firing. The injectors are electronic and not mechanical.
because it's electronic you don't really need to be "jumping" anything. In doing so, it'd be real easy to fry the ecu via backfeed. And ecu's are not cheap, easy to get, or fun to replace.
ideally you need a wiring diagram and also need access to the hardware and software that will connect to the tractor's ecu, so it can be read and then you can figure out what ain't doing what. But since you don't have that, you have several choices. Throw parts at it. Hire a certified shade-tree mechanic. Fiddle around with it using certified youtube mechanic's guiding, or take it to a dealer and let them figure it out. Option #1 and #2 could very easily cost you a few thousand dollars. Option 4 could too...or they could have it figured out in about 10 minutes...never know.
I didn't read all the replies. Did ya check the fuses?
Ok my new Orange friends, I tested the relays and found that I was not getting a ground signal from the ECU to the the relay for pressure pump and fuel switch solenoid. So i jumped the ground to the relay and the pump came on and the solenoid had power. Unfortunately, it would not start... From what I gather, this is an ECU issue. Do you agree? So what is protocol from here?
Good work. Yes, it's an ECU issue.
Now, what ECU issue? I see two possibilities:
You can start by verifying function of your safety switches. But you could have a good switch that has a pinched wire leading to the ECU. That means you could test the switch and call it good, but still no worky.
Gotta get a wiring diagram.
Now, what ECU issue? I see two possibilities:
- The ECU is fried. Not common, but it does happen. Not cheap, either.
- The ECU is not getting some signal it wants to see before it will allow the engine to start. That could be a safety switch or maybe an engine condition sensor of some kind. This could be cheap, or low cost. Much cheaper than an ECU, anyway.
You can start by verifying function of your safety switches. But you could have a good switch that has a pinched wire leading to the ECU. That means you could test the switch and call it good, but still no worky.
Gotta get a wiring diagram.
The ecu is not trying to trigger the relay. i checked all the connections from the ecu ect,. I'm pretty sure it is in the ecu. would this be a programming issue? how can this be fixed? is the ecu bad and need replaced or fixed? I was told that the ecu has to be reprogrammed while on the tractor, but I don't trust the source. how do i fix this?
As far as the safety switches< hst,pto, clutch , brajke, ect, seem to be working because it will spin over or not depending on the switch on or off and i checked them individually. I am trying to be as precise as possible as wiring is a nightmare to me. i understand it mostly but i can never be sure if I'm overlooking something. is there a place i can send the ecu for testing?
The ECU is not providing a ground to the relay. I jumped a ground to it and the fuel pump came on . i tried to crank it but it will not fire. Does the ECu send its signal to the injectors individually?
the ecu ground issue could be a fault in the ecu or a software strategy if it sees another concern else where. Yes the ecu controls the injectors individually. You are basically pissing into the wind without having a scan tool to see what is going on…
Yes, according to another poster on this thread. My guess is that it's providing ground to the injectors when it wants to fire them. If that's the case, they should have 12v to them whenever the key is on. You can check that easily.
But since it's not providing ground signal to the relay, it's probably safe to assume:
1. The ECU ground is not grounded properly, so cannot provide a good ground, OR,
2. The ECU is not getting some signal that it needs to give the go-ahead, OR,
3. The ECU is fried.
#1 is not likely, as it seems to be working otherwise. Gauges work, correct?
#2 is quite possible and would need a shop manual to diagnose.
#3 is also possible. It's a bit expensive to just buy a new one in hopes that it will fix the problem, so I suggest you do a quick check for #1, and then get that shop manual so we can move forward from there to see if #2 is the problem.
Before you cost yourself a lot of money screwing around with a system you don't understand, even though learning by doing is usually a useful strategy, re read lugbolt's advice. He actually has spent a lot of time repairing this model tractor as a job. You need software and hardware to connect to the ecu. Something small may have gotten screwed up when you replaced the ignition. You can easily wreck an expensive pump or an expensive ecu jumping things. Unless you are marooned on a tropical island, consider hauling it to a dealer.
I understand and you are right. I dont have a way to load it right now. Ill need another tractor to do so.
Injector voltage will be around 110 volts… I would also guess it wouldn’t even try to power an injector if it’s not powering the pump.
Interesting. Where's it getting 110 volts? More importantly, why, on a 12v system? 12v will power an injector without any problem.
Agreed. The ECU clearly isn't happy, so it's not letting anybody have a good time. I mentioned it really as a matter of curiosity.
Providing a ground ("jumping" a ground) won't hurt anything. Jumping 12v here and there might, but not ground. And as long as he's using a meter to measure voltage, and not a test light, he won't hurt anything that way, either.
Certainly having diagnostic software is the best way to get from A to B, but since that's not an option, he can get there by doing simple measurements and tests, IF he has the manual so he knows what he should be seeing.
Thank you! I'm guessing they are using a singer circuit to raise the voltage, then. Not complicated.
So it looks like they are supplying voltage constantly, and switching ground to actuate the injectors. That's a common configuration.
I'm with you - I'll bet he won't find that 110 at the injector, either.
So it looks like they are supplying voltage constantly, and switching ground to actuate the injectors. That's a common configuration.
I'm with you - I'll bet he won't find that 110 at the injector, either.