TL-A series fuel solenoid circuit

[Buck Farack]

I'm hoping that some of you familiar with these cab models can help me figure out a problem with the fuel solenoid circuit. I'm blowing the 5 amp fuse intermittently. Apparently, it is happening on start-up because it has never died in use - only fails to start occasionally. All I have to do is put in a new fuse and it will start just fine. Just over 3,000 hours, and I can't find anything wrong with the wiring that I can see.

It doesn't seem to me as if a 5 amp is really big enough, but that's what it calls for and I've never had any problems until lately. Is it possible that the solenoid is just drawing more as it gets older? Battery is less than two years old, all grounds and connections look to be in good shape.

I hate to replace the solenoid until I just absolutely have to, so I've thought about stepping up to a 7.5 or maybe even a 10 amp. Or even trying a breaker in place of the fuse. I can't see anything that would make me think that a 10 amp would be too big, but I'm not sure what all is on the circuit. Any thoughts?

Thanks.

Buck

 

[jinman]

Buck, it's hard to find them in the open market, but I think New Holland has a 7.5 amp or 8.0 amp self-resetting circuit breaker that is an exact replacement for a fuse. If you want to buy them from Grainger, this 6 amp CB would be almost a perfect replacement. You can do an internet search for "Cooper-Bussman UCB-6" to find other sources. Just add the number after "UCB-" that you want to replace. For example, UCB-10 = 10a and UCB-20 = 20a.

Now, to your problem. I don't think your fuel solenoid is the problem. Most solenoids I'm aware of have a pull-in current of just over 1 amp. Two amps would be a huge amount of pull-in current. Are you sure that the solenoid is the only thing on the circuit? For many years, I thought my fuel solenoid was the only thing on my tractor's circuit. One day, I did a detailed circuit analysis and discovered that the starter solenoid was also on the same circuit. Not full starter current, but just the current that pulls in the solenoid to make the starter operate. That solenoid could/would hang from time-to-time so that it did not fully engage. Because it is a dual current solenoid (high pull-in current and low hold-in current) it would stay in high current mode and blow the fuse. By replacing the fuse with the self-resetting circuit breaker, I solved my problem. The CB popped when the circuit was overloaded, but reset for another try. Most of the time, on the 2nd or 3rd try, the solenoid fully engaged and everything operates normally. I have no way of knowing if your circuit is similar, but it's worth investigating. The CB is really worth the money if you are just having an intermittent failure. You can measure your solenoid's resistance to ground by disconnecting and using an ohmeter. Most of them are around 12 ohms. (Volts/Ohms = Amps, so that would be 1 amp.)

 

[Buck Farack]

Thanks for your reply, Jim. That's good info to have about the solenoids only pulling one amp. So the factory 5 amp fuse should be plenty big even if it doubles.

I'm not sure what else is on the same circuit, I was hoping that somebody here might either know from having a similar experience, or have a wiring diagram to check for me. I don't think the trigger for the starter solenoid would be on that circuit because it was cranking over just fine when the fuse was blown - just not getting any fuel to start.

Good tip on the breakers - I'll try to look for one of those in a 6 amp. In the meantime, I might step up to a 7.5a fuse if I have any more trouble. It's really intermittent - only happening twice out of the last 12-15 starts. I'll also check into some of the safety stuff to see if I can find some of it on the same circuit as the fuel solenoid.

If you or anybody else have any more thoughts or speculation, I'm all ears...

Buck