Mahindra eMax25L HST blows fuses when starting

[Mike1955]

I wonder if it could be the starter relay?

Surely the relay itself draws way less than that. Maybe glow plugs might

 

[Mike1955]

If the glow plugs are labeled to the fifty amp fuse, stands to reason the 40 amp is labeled, somewhere. Got me wondering now

 

[bbocaner]

The 40A fuse that is blowing is the main fuse.

 

[Mike1955]

But the glow plugs are on a fifty. Maybe it’s been tampered with. Could the alternator be blowing it. There ain’t that many high current devices on there. Lights, to they come on automatically? Fuel solonoid? The stuff is so compacted it difficult to run down

 

[K5lwq]

Maybe replace the fuse with a light bulb and try it. If it is a short the bulb will light up. Then keep disconnecting things or wiggling wires till the light goes out. Once it goes out you found the problem.

 

[bbocaner]

But the glow plugs are on a fifty. Maybe it’s been tampered with. Could the alternator be blowing it. There ain’t that many high current devices on there. Lights, to they come on automatically? Fuel solonoid? The stuff is so compacted it difficult to run down

I traced out the basics...

A thick wire goes from the positive terminal on the battery to the starter.

The same terminal on the starter you have a wire coming back to the 40a main fuse (by the battery, in the front of the tractor)- the other side of this fuse goes to the ignition switch and the fuse panel (on the side of the engine, next to the ECU)- I think probably to power the glow timer which could be on if the ignition switch is not.

Then the terminal on the starter also has a wire coming back to a 50a fuse, the other side of which goes to the glow plug relay.

And then there's a fourth wire to the same terminal on the starter which has a wire coming back to a second 50a fuse, the other side of which goes to the alternator.

So if I understand correctly, the 40a fuse that is blowing does not have any relation to the alternator. The lights are off. I'll have to see if I can figure out how the fuel system works.

I have verified with photos I've found on this forum that other people with the same tractor have the same 40a,50a,50a (green, red, red) fuse setup in the front of the tractor - so I know it hasn't been modified.

 

[ning]

Could be a glow plug short? Unlikely, but... can you easily disconnect them and see if the fuse still pops? (how many fuses do you have left...)

 

[ruffdog]

So the alternator and glow plugs have their own 50a fuse circuits. The 40a fuse pops during the engine crank mode only? I'm wondering about the "pull" circuit of the fuel solenoid as that is activated during cranking. After starting, it would then go to the "hold" circuit of the solenoid.

 

[Mike1955]

Could be a glow plug short? Unlikely, but... can you easily disconnect them and see if the fuse still pops? (how many fuses do you have left...)

He doing some classic trouble shooting. And he is getting closer by isolating. I wish I was there to help him

 

[bbocaner]

Thanks for the moral support, @Mike1955 ! I wish you were here to help, too.

We got it running! We unplugged everything that we could get unplugged (a lot of the connectors were stuck and we couldn't get them apart) and plugged them back in one at a time until the fuses started blowing again. The culprit was a mysterious component about an inch by and inch and a half, with a small flange on it to be screwed to the frame of the tractor, on the right side of the engine just in front of the dashboard. It has a small nipple-shaped protrusion on the backside, facing--but not touching the air intake hose. I cannot find this part on any of the Mahindra or TYM (the tractor's OEM manufacturer) parts diagrams.

Here's a photo:

I think it may be some sort of air temperature or pressure sensor, but I can't find anything online about this model having such a thing. I did read about a temperature sensor that can sometimes short out and cause fuses to blow, but I thought that was a coolant temperature sensor, and I thought that was on top of where the coolant line comes out of the block to go to the radiator.

I'd like to be able to just order another one but I need to figure out what it is first. Does anyone know?

And in another wrinkle, the low oil pressure light was doing a little bit of flickering while we drove it up to park in the shed for further troubleshooting and reassembly. Could this sensor we unplugged have anything to do with oil pressure?! I don't see how, but I don't see any other sort of oil pressure sensor screwed into the engine anywhere else either. Or maybe what I thought was a coolant temp sensor (which is still unplugged) has something to do with it.

 

[ruffdog]

When looking at a parts look-up site, one of the wire harnesses had an item in that location...a Barometric pressure sensor. The thing is, that item, what ever it is, may not be the real problem. The problem may be whatever this is controlling. Maybe unplugging this puts the ECU into a different mode that bypasses the issue. The oil pressure light flickering is disturbing.....

https://parts.mahindrausa.com/dealerview/illustration.aspx

 

[bbocaner]

oh wow, thanks @ruffdog !! Which diagram did you see it on? I looked and looked and didn't see it!

 

[Mike1955]

So glad you got to that. Heck a dealer should be able to get one and know its purpose. Good luck and I’ll bet that oil light flashing has nothing to do with that. It looks like it would have to be something to do with temp or humidity. No oil line was attached to it. I hope it don’t damage it without it. Maybe it’s a capacitor to clean up the alternator output voltage or even a transistor. Were three wires attached to it? Looks like two. Thanks for sharing

 

[ruffdog]

Is the item in question near the ECM, fusebox, and relay? If it is, the only other item is the barometric pressure sensor.

 

[ruffdog]

oh wow, thanks @ruffdog !! Which diagram did you see it on? I looked and looked and didn't see it!

It was under chassis and one of the wire harnesses.

 

[bbocaner]

OK, so this is really weird.

My wife and I did an oil change and put a new filter on, hoping to solve the oil pressure light. No good, the oil pressure light was still flickering, even after running a few minutes and starting a few times.

So, I plugged the barometric pressure sensor back in, and after about 10 seconds the light went out and stayed out. Unplugged the sensor and the light started coming on again. This sensor is attached to the frame of the tractor and isn't anywhere close to oil... so I'm confused as to what the connection is.

And now it's starting just fine without blowing fuses with the sensor plugged back in again!! So weird...

 

[ruffdog]

You fixed it!