CK 450 blowing fuse

   / CK 450 blowing fuse #1  
T

tysmobiletractor

Member
Joined
May 31, 2016
Messages
40
Location
Amherst Wisconsin
Tractor
Ford 641 / 1963 Fordson Super Major
When the key is turned on it blows the fuse “ fuel solenoid “. 25 amp 2 nd fuse from the top.
I’ve been investigating the harness. No problems visible.
when I unplug the fuel solenoid, it does not blow the fuse. How can I test the solenoid?
 

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   / CK 450 blowing fuse #2  
I'd begin by using an ohmmeter. The solenoid may be good itself but have the coil shorted to ground internally. One end of the coil may be at ground but if the other end gets grounded, too, you will have a dead short to ground. I have a slow internet connection and can't load your pictures but the middle one appears to show potential for shorting to ground. If that's the solenoid you could try turning on the key with it not mounted but connected to the wiring. The resistance of a circuit to blow a 25 amp fuse at twelve volts is pretty low - something in the vicinity of half an ohm.
 
Last edited:
   / CK 450 blowing fuse
  • Thread Starter
#3  
Ok, Thanks.
I was thinking, of doing a continuity test between the fuse outgoing side to the harness plug for the solenoid. I should be able to identify a good continuity reading on one wire if the harness is not damaged or broken.
Before I pull the solenoid off.
I think there should be 2 power wires, one high voltage to pull the valve open, and a second to hold it open. The 3rd would be a ground.
Anyone, clarify this, if I'm missing something.
Low voltage wire should be constant. For running continuous.
High voltage wire for initial opening of valve on start up.
 
   / CK 450 blowing fuse #4  
I know nothing about your tractor. I would expect the start winding to have lower resistance to permit more current flow. The run or hold winding should have a higher resistance which would limit current flow. Unless you have some kind of power amplification circuit the applied voltage to each would be twelve volts. It is possible to have one shorted winding or one winding shorted to ground while the other is normal.
 
   / CK 450 blowing fuse
  • Thread Starter
#6  
So, here's an update.
I have good readings on the plug feeding the solenoid.
The pull side is showing power for about 3 seconds and then goes off, I can hear the relay click when this happens. That is expected. This should open the fuel valve at startup.
The hold side wire has continuous power anytime the key is on. Even when the fuse is blown, or removed. This should allow fuel to continue to flow.
This all seems correct, as it should.

This being the case, I moved onto testing the fuel solenoid.
I removed it and hooked up a ground wire from the battery to the exterior of the solenoid.
The pull side, high voltage with the larger wire, seems to have a direct short out inside. When I jump power to this pin, it is a like a dead short! Not good.
The hold side pin, if I push down on the plunger and connect power to this pin, it holds the plunger in, when I remove the power, it releases the plunger and it springs back all the way out.

So, low voltage side is holding, but high voltage side is bad!

I installed a new one.

When I tested it I could hear it click. So, I started it, and it started fine. Ran great for about 6-7 minutes. Then it quit running on its own. I checked and it blew the same fuse again. And I can feel the solenoid was really hot!

Put in a new fuse, and as I suspected, it blew the 2nd fuse. Back to the same place I was before. Bad fuel solenoid.
So, now, what is causing this?

Could a bad relay cause this?

It seems possible, except for the fact that the harness is working properly when I test the plug with it off the solenoid. Why or how can it be an issue when it is connected?
 
   / CK 450 blowing fuse
  • Thread Starter
#7  
Tested the relay.
It tests fine. It not only clicks, so I know the circuit is closing, but it has good ohms reading and is allowing current to flow through the switched connection.
So, it should be all good.

Now, what?

I would think, maybe its the low voltage side, that is the problem? But, the fuse that blows is not on that circuit. The fuse that blows is only on the high voltage pull wire circuit.

Any ideas?
Or experience on this issue?
 
   / CK 450 blowing fuse
  • Thread Starter
#8  
I did test this relay, to verify it is the correct one.
The manual shows it to be the 3rd one in from the outside of the firewall. But when I unplugged that one, there was still power to the Pull side.
So, I unplugged the middle relay. Then there was no power to the pull side on the plug to the solenoid.
So, that is the one I'm testing.

Unless I'm missing something here.
 
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