Fuel cut off solenoid

Frostbyte

Member

Equipment
B7800HSD
Jun 20, 2017
35
3
8
Chesapeake VA
I searched the forums and didn't find my specific issue so I'm starting a new thread ...

I have a B7800 (that I really like a lot, bought used with 250 hrs on it) that has had various issues due to being stored outdoors all its life.

The current issue is with the fuel solenoid. Intermittently it will "stick" in the off position. It never sticks for very long and once I hear that distinctive sharp "click" she starts right up in any weather.

I've learned to listen for that click when I turn the key on. If I don't hear it she's gonna crank but won't start. Presumably due to lack of fuel.

I can leave the key on and go grease whatever implement (usually an ancient, decrepit finish mower deck) and while I'm doing that I'll hear the fuel solenoid go CLICK! and then the tractor will start just like it should. So it's never more than a few minutes between turning on the key and when the fuel solenoid disengages and the tractor will run.

Then it stays running just fine.

It doesn't do this every time, only about one out of ten startups if that.

I discovered the solution because I shut it off once and then it wouldn't start. I accidentally left the key on and while I was tinkering around with some other stuff I heard the telltale CLICK! The tractor started up after that so I've made a note of listening for the click before cranking and if I don't hear it I don't crank until I do.

If I do not hear that CLICK then it most certainly will crank but not start. This also seem to me to rule out any safety switch issues. If a safety switch is active (like having the PTO engaged) it will not crank.

It almost acts like it needs to have the key on and "warm up" for a few minutes when this happens. I'm thinking that might be a relay or some such. It doesn't matter what the ambient temperature is. It will do it in the heat of summer or the dead of winter and the symptom is the same. It also doesn't matter if the engine is warm or not, nor if it has been run recently or has sat for a while.

It has a new battery as of this summer and the battery is charging up just fine via the onboard alternator/dynamo, whatever it's called on this engine.

So what I'm wondering is if anyone else has had this issue and if so how they solved it? I can put a new fuel solenoid on it, that's not a problem but they're kind of spendy so I don't want to buy one just to find out that it's something else.

It's not a real big deal, the time elapsed from turning on the key to when that solenoid goes CLICK! is never more than just a couple of minutes.

I probably wouldn't even bother except that I'm concerned whatever the problem is -- It's going to fail completely one day and I won't be able to start my little tractor until I buy and install either a relay or a new solenoid. Which means waiting for a part to get here. I'd rather get it fixed before that happens and I need to use it but can't someday.
 
Last edited:

North Idaho Wolfman

Moderator
Staff member
Lifetime Member

Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
28,286
4,853
113
Sandpoint, ID
That was a heck of a lot of explaining! :p

Yes the solenoid is bad/weak and needs to be replaced.
 

thepumpguysc

Member
Aug 8, 2018
267
1
16
Sunny South Carolina
Check your electrical connection & sand accordingly. There are a lot of cases where that connection becomes loose & corrodes, & people have gone so far as to zip tie the connection.
Take the sol. out & if the plunger will come out of the center, inspect the plunger & clean the inside area w/ lite grade sand paper or a scotchbrite pad..
The solenoid is just one of the weak points in that system.. thousands of threads/posting on the web about them & the cost.. Some folks opt to search & find an aftermarket sol. on fleebay..
I'd try the sanding/cleaning method first.. as that symptom/starting procedure is not correct..{its not supposed to be that way}
 

Frostbyte

Member

Equipment
B7800HSD
Jun 20, 2017
35
3
8
Chesapeake VA
That was a heck of a lot of explaining! :p

Yes the solenoid is bad/weak and needs to be replaced.
Sorry, I was trying to be as thorough as I could, figuring that more information was better ...

I see Amazon has an aftermarket solenoid that is a little less than half what they want for one at Messicks. It has a one year warranty. I'll try one of those and keep the old one for a stopgap replacement in case it fails and I have to wait for a new part.

Thanks for your help, again.
 

Frostbyte

Member

Equipment
B7800HSD
Jun 20, 2017
35
3
8
Chesapeake VA
Check your electrical connection & sand accordingly. There are a lot of cases where that connection becomes loose & corrodes, & people have gone so far as to zip tie the connection.
Take the sol. out & if the plunger will come out of the center, inspect the plunger & clean the inside area w/ lite grade sand paper or a scotchbrite pad..
The solenoid is just one of the weak points in that system.. thousands of threads/posting on the web about them & the cost.. Some folks opt to search & find an aftermarket sol. on fleebay..
I'd try the sanding/cleaning method first.. as that symptom/starting procedure is not correct..{its not supposed to be that way}
Hi and thanks for your suggestions. I had already gone over all the contacts, thinking that might be it. They are all bright and tight.

I hadn't pulled the solenoid yet. I'm going to get a new one and install it, when I do that I'll see what I can do about cleaning up and refurbishing the old one for a stopgap fix.

Because I'm going to order an aftermarket solenoid from Amazon that's about half the price of an OEM from Messicks etc. I'm willing to take the chance that it's the solenoid. Even so, I'll feel better about ordering an el-cheapo aftermarket if I have the old one which still works the great majority of the time.

I'm thinking that way I probably won't get stuck waiting for a part if the new one fails.

Thanks again.
 

HHH3

New member

Equipment
B8700
Mar 15, 2024
1
0
1
Virginia
Hello,
Can someone tell me how many safety switches are on the B7800 model?
My tractor stopped running after it hit 'hard' while running the PTO with a bush hog on the back one day and started to stutter and stop a few times. I let it set after dropping the cutter and disengaged the PTO. Never started or turned over since. So far I have since replaced everything, solenoid, starter, relay, dynamo, under seat safety switches, two of safety switches for PTO and belly/mid PTO. Battery is a year od and I have lights and all power works. Key start turns on, 1,2 3 for glow plugs but nothing...no crank over.
Any ideas would be appreciated.

Thanks
Hal