B7510 intermittent start problems

[Ldfd5701]

Hey everyone I’m scratching my head on this one. In other forums people have commented that the fuel shut off solenoid receives power to kill the engine. This B7510 is opposite. I’m having intermittent start problems. Engine turns over every time I turn the key. Sometimes the fuel shutoff solenoid clicks when you turn the key to on. When it clicks it will start. If it doesn’t click, no start. If it doesn’t click and I apply power to the fuel shutoff solenoid it will click and start.
I’ve checked all the safety’s and they are good, even temporarily bypassed them to confirm I didn’t have and intermittent switch problem. I’m tempted to bypass everything and add a switch to power the fuelshutoff directly but I’d prefer to keep the safeties intact since I’m not always the one on it. Help!

 

[GeoHorn]

sounds like you need to find the intermittent connection to the fuel solenoid.

 

[Ldfd5701]

sounds like you need to find the intermittent connection to the fuel solenoid.

Gee thanks for the help

 

[Dave_eng]

Gee thanks for the help

No need to get frustrated. Everyone on this forum works hard to keep things polite.

I can offer some comments which may help. The stop solenoid on your engine is more complicated than you might realize. It has two internal coils and each is powered at a different time during the start cycle.

There is a PULL IN coil which is strong, uses lots of amps and should not be energized for more than a couple of seconds or burn out is likely.

There is a HOLD coil which is weak. It has just enough strength to hold the internal plunger in position once it has been moved by the PULL IN coil.

The solenoid is grounded by its body contacting the engine. When you apply power, which of the two coils are you powering. The wiring connector has two terminals. Neither is a ground!

How are you maintaining power to the solenoid to keep the engine running?

I find the wiring diagram for the B7510 misleading. The two power wires join together.

I suspect there is an internal switch which breaks the pull in coil's circuit as the plunger moves.

I have posted previously on this topic regarding a B7800 and I have attached my comments.

Do you have a 12 volt test light? A cheap tool which can help you figure out which of the two internal circuits may not be working.

Once you answer the questions posed it may be possible to help you zoom in on the problem.

Dave

 

[Ldfd5701]

Hi Dave. Thanks!
when the tractor is in it’s no start condition I don’t have power to either side of the connector. The solenoid has a good solid ground to the engine. If I apply power to both solenoid terminals with my test leads the tractor will start. I only let it run for a second assuming that the two coil solenoid wouldn’t like constant power to both sides. I just ordered a shop manual so I can have wiring schematics and Kubotas test procedures. It appears the problem is in between the safety switches and the Fuel shutoff. According to some of the info I’ve been able to dig up online it says there is a shutoff relay and a OPC in between. I’ve not been able to locate the relay and I’m wondering if the OPC does the relays function as well. The only thing I’ve been able to find on the OPC is that if everything else checks out ok to replace it. I’d really like to know for sure before I throw a $200 part at it.

 

[Henro]

Hi Dave. Thanks!
when the tractor is in it’s no start condition I don’t have power to either side of the connector. The solenoid has a good solid ground to the engine. If I apply power to both solenoid terminals with my test leads the tractor will start. I only let it run for a second assuming that the two coil solenoid wouldn’t like constant power to both sides. I just ordered a shop manual so I can have wiring schematics and Kubotas test procedures. It appears the problem is in between the safety switches and the Fuel shutoff. According to some of the info I’ve been able to dig up online it says there is a shutoff relay and a OPC in between. I’ve not been able to locate the relay and I’m wondering if the OPC does the relays function as well. The only thing I’ve been able to find on the OPC is that if everything else checks out ok to replace it. I’d really like to know for sure before I throw a $200 part at it.

Since you mention the solenoid has two terminals, chances are one is for the start (or pull in) coil, and the other is for the Run (or hold in) coil.

First thing you need to do is verify what voltage is on each terminal when the key is turned to the on position, and also when the key is in the start position. Generally, the hold coil will be energized in both key postions, but the start coil will only be energized when the starter is turning.

Knowing this will give some hint of what the next troubleshooting step might be. On my BX2200, the solenoid grounds to the engine block, and that is the path to ground for both solenoid coils. I assume, but do not know, that your tractor may share this set up.

 

[Ldfd5701]

Since you mention the solenoid has two terminals, chances are one is for the start (or pull in) coil, and the other is for the Run (or hold in) coil.

First thing you need to do is verify what voltage is on each terminal when the key is turned to the on position, and also when the key is in the start position. Generally, the hold coil will be energized in both key postions, but the start coil will only be energized when the starter is turning.

Knowing this will give some hint of what the next troubleshooting step might be. On my BX2200, the solenoid grounds to the engine block, and that is the path to ground for both solenoid coils. I assume, but do not know, that your tractor may share this set up.

It appears that is the setup with the B7510 as well. The problem has become constant no start so that should help with diagnostics. My manual should be here tomorrow or Thursday that should help considerably. I did find a spot where a mouse decided he wanted my wire insulation for his home so I may have a bad wire. Oddly it hasn’t blown a fuse if that’s the case it’s just open and not shorted to ground.

 

[Henro]

It appears that is the setup with the B7510 as well. The problem has become constant no start so that should help with diagnostics. My manual should be here tomorrow or Thursday that should help considerably. I did find a spot where a mouse decided he wanted my wire insulation for his home so I may have a bad wire. Oddly it hasn’t blown a fuse if that’s the case it’s just open and not shorted to ground.

I believe the workshop manual will tell you how to check the solenoid for proper operation. This will require removing the solenoid so you can see what the armature rod is doing. When you find the solenoid is working correctly, you will then have to make voltage measurements to see what the root issue is.

I do not know for sure, but I am pretty sure the first measurements you will need to take are the voltages being applied to the two wires feeding the solenoid.

So I would (myself, if it were me ) get a head start and just check those voltages. Chances are that wire might be broken (the one the mouse attacked). A wire even if uninsulated, if hanging in the air, will not cause a blown fuse. Neither will a broken wire that is hanging loose in the air.

Voltage measurements on the wires feeding the fuel cutoff solenoid will be your friend as you trouble shoot the problem.

When you applied voltage to both wires feeding the solenoid you pretty much ensured that the solenoid is operating properly. BUT it still could have a bad hold coil. The perfect test would have been to apply voltage to both wires, and then remove the voltage from the start coil wire.

I am sure you will solve the issue...eventually...if not quickly.

 

[dcarter]

I'm having the exact same problem with my L2501. Let us know if you find the cause. I'm going to remove the selenoid and do some voltage testing now, but I believe it's probably a bad relay. I'm not seeing much info on this relay online. I have the PDF shop manuals but it's really hard to navigate.

 

[Ldfd5701]

I believe the workshop manual will tell you how to check the solenoid for proper operation. This will require removing the solenoid so you can see what the armature rod is doing. When you find the solenoid is working correctly, you will then have to make voltage measurements to see what the root issue is.

I do not know for sure, but I am pretty sure the first measurements you will need to take are the voltages being applied to the two wires feeding the solenoid.

So I would (myself, if it were me ) get a head start and just check those voltages. Chances are that wire might be broken (the one the mouse attacked). A wire even if uninsulated, if hanging in the air, will not cause a blown fuse. Neither will a broken wire that is hanging loose in the air.

Voltage measurements on the wires feeding the fuel cutoff solenoid will be your friend as you trouble shoot the problem.

When you applied voltage to both wires feeding the solenoid you pretty much ensured that the solenoid is operating properly. BUT it still could have a bad hold coil. The perfect test would have been to apply voltage to both wires, and then remove the voltage from the start coil wire.

I am sure you will solve the issue...eventually...if not quickly.

Everything is pointing to the OPC. Unfortunately the shop manual I ordered doesn’t have a wiring schematic. I’ve tested all of the safety switches, the shutoff solenoid is good, I have 0 voltage to the shutoff, I have good continuity between the OPC plug and each individual switch. Gotta be the OPC but I really hate to buy a $200 part without knowing for sure!