B7800 solenoid question

[curiousgeorge]

Hello everyone,

When I try to start a B7800 should the center pin of the stop solenoid extend or retract while I am cranking the engine? I had posted another thread where I was suspecting the clutch safety switch, but since that did not seem to be the problem, I replaced the solenoid last night with an OEM Kubota solenoid. It still just cranks and does not start.

I plugged in the old solenoid to see if I get any action when cranking the engine, and that pin does not move at all when I crank the engine. I suspect that means that the starter relay is bad, so I ordered one, but I am just wondering if the solenoid center pin should move at all while I am cranking (when all else is working).

I guess I could pull the new solenoid for the same test, but it was a bit of a pain to get that back screw on.

Thanks,

CuriousGeorge

 

[JerryMT]

When you are cranking and in the run position, the solenoid should stay in the position that provides fuel to the injection pump

 

[wgator]

Below is from the workshop manual for you tractor. According to it the plunger should pull in to run engine. If you don't have the wsm download it free BY CLICKING HERE. Read pdf page 393 to understand how to use the manual for B7800.

 

[curiousgeorge]

Thank you very much! So if I remove the solenoid completely should fuel flow to the injectors?

From looking at the WSM it appears I should have used a liquid gasket to install the WSM, so I will remove the new solenoid and test it as well. Does the solenoid body have to touch the engine body for ground (when I test)? There are two white wires in the plug, but maybe neither is ground. When I plugged the old solenoid back in, I just had it laying on the tractor.

 

[Dave_eng]

Thank you very much! So if I remove the solenoid completely should fuel flow to the injectors?

From looking at the WSM it appears I should have used a liquid gasket to install the WSM, so I will remove the new solenoid and test it as well. Does the solenoid body have to touch the engine body for ground (when I test)? There are two white wires in the plug, but maybe neither is ground. When I plugged the old solenoid back in, I just had it laying on the tractor.

The solenoid has two internal coils both relying on the solenoid body's contact with the engine for a ground.

If the solenoid is not receiving power then either the engine stop relay is bad or the OPC controller is bad.

Dave

 

[Russell King]

From other people’s post on similar parts the case is often the ground point. If you have two white wires I believe you will have a run coil and a stop coil. The WSM should have a trouble shooting section to help walk through testing.

 

[whitetiger]

I posted this to your other thread.

 

[curiousgeorge]

Thanks again everyone! Yesterday I took the plastic housing off (with the instrument cluster) and found some very shoddy electrical repair (electrical tape partially covering wires where the insulation was probably chewed off by mice). All four of the wires going to the start relay were chewed and some were undoubtedly touching each other as the electrical tape had mostly fallen off. A couple of the blades on the relay look like they had been very hot as they look burned orange. I have two relays on order and hopefully that will be the solution.

I replaced the chewed up wire sections, taped them all the way and covered them with flexible split loom although I hope they will not be visited by mice again.

Will update after replacing the relay.

 

[curiousgeorge]

Thanks again everyone! Yesterday I took the plastic housing off (with the instrument cluster) and found some very shoddy electrical repair (electrical tape partially covering wires where the insulation was probably chewed off by mice). All four of the wires going to the start relay were chewed and some were undoubtedly touching each other as the electrical tape had mostly fallen off. A couple of the blades on the relay look like they had been very hot as they look burned orange. I have two relays on order and hopefully that will be the solution.

I replaced the chewed up wire sections, taped them all the way and covered them with flexible split loom although I hope they will not be visited by mice again.

Will update after replacing the relay.

I ran the relay test from page 362 of the WSM and I am getting 84 Ohms so according to the WSM the relay is bad. Looking forward to the new relay!

UPDATE on the orange blades on the relay... from looking at a few internet pics, two of the blades are supposed to look orange, so they are not that color because of getting hot.

 

[Dave_eng]

I ran the relay test from page 362 of the WSM and I am getting 84 Ohms so according to the WSM the relay is bad. Looking forward to the new relay!

UPDATE on the orange blades on the relay... from looking at a few internet pics, two of the blades are supposed to look orange, so they are not that color because of getting hot.

But with the burned wires in your photo, the contact points in the relay may be damaged,

Dave

 

[curiousgeorge]

But with the burned wires in your photo, the contact points in the relay may be damaged,

Dave

It looked like the insulation was just chewed off the wires, but they didn't look burned.

Just received the new Kubota start relay and it cranked right up I cranked it up about a dozen times.

So it looks like it was the relay, but I am glad I opened it up because those bare wires would have caught up with me eventually. And I wrapped and covered with wire loom the other wires that were exposed. Thank you everyone for your help!

 

[Dave_eng]

It looked like the insulation was just chewed off the wires, but they didn't look burned.

Just received the new Kubota start relay and it cranked right up I cranked it up about a dozen times.

So it looks like it was the relay, but I am glad I opened it up because those bare wires would have caught up with me eventually. And I wrapped and covered with wire loom the other wires that were exposed. Thank you everyone for your help!

Glad you are back in operation

Dave