Bobcat CT445 Fuel Solenoid Issue

[1maddog1]

I have a Bobcat CT445 SST that does not start, turns over fine. Troubleshot down to the fuel solenoid not actuating. My understanding is this... the solenoid works on a three wire hookup...center wire is GRND, one outer wire is a momentary 12v to initially actuate the solenoid when the key is turned to the "on" position and the other outer wire is a constant 12v to hold the solenoid in the actuated position until power is removed by turning the key off. At the solenoid I get a momentary 11.55v when the key is turned on but the solenoid doesn't actuate. If I disconnect the solenoid and just use jumpers from the battery....jumpering a constant 12v to one pin,Grnd to the center pin and quickly tap the momentary pin with another jumper the solenoid works fine. Just to add everything I've checked, all fuses check good, all safety switches are good. I have even replaced the solenoid and the fuel relay with no change. Any help would be greatly appreciated.

 

[k0ua]

I have a Bobcat CT445 SST that does not start, turns over fine. Troubleshot down to the fuel solenoid not actuating. My understanding is this... the solenoid works on a three wire hookup...center wire is GRND, one outer wire is a momentary 12v to initially actuate the solenoid when the key is turned to the "on" position and the other outer wire is a constant 12v to hold the solenoid in the actuated position until power is removed by turning the key off. At the solenoid I get a momentary 11.55v when the key is turned on but the solenoid doesn't actuate. If I disconnect the solenoid and just use jumpers from the battery....jumpering a constant 12v to one pin,Grnd to the center pin and quickly tap the momentary pin with another jumper the solenoid works fine. Just to add everything I've checked, all fuses check good, all safety switches are good. I have even replaced the solenoid and the fuel relay with no change. Any help would be greatly appreciated.

Well now that is a good one. Yes you have a perfect understanding of how it works. Are you sure your replaced the fuel solenoid relay, (third one from the left on the firewall,) First one is the start relay, then the glow relay (it is the 70 amp rated one) then the fuel solenoid relay, If that relay clicks it allows about 30 amps of current to go to the "pull" coil of the actual fuel solenoid for the 1 second, and then the "hold" coil which is powered by the key thru the 10 amp fuse will hold the solenoid back against spring pressure with only about 3/4 of an amp of current. Is it possible the center ground wire on the solenoid connetor has a poor connection ?. High resistance on the relay connection or thru its contacts? You can instantly substitute relays by swapping harness of the start relay (cranking relay) and the fuel stop solenoid relay.. These are the type of things that try mens souls. Are you sure the fuel stop solenoid relay (3rd relay from the left) is clicking up?.. damfino what else is wrong here. I am scratching my head and scratching my rear and I ain't coming up with much here..


James K0UA

 

[1maddog1]

Indeed I did change the fuel relay(third from left), at first I swapped the harness then when I bought a new solenoid I also purchased a new relay and installed both with no change in symptom. This whole thing started one morning I loaded it up onto a trailer, It started just fine. I loaded it up and drove to my destination. When I went to start it to get off the trailer it was very hard starting and ran sluggish. I finished the job and shut it off. when I went to start it again about an hour later to load it back up is when it wouldn't start. I had to pull the solenoid out of the motor to start it, then once on the trailer I had to stall it out to shut it down.

 

[k0ua]

I wonder if for some reason in the wiring harness there is enough resistance to limit the current on the Pull coil so that it cannot be fully pulled back so that the hold coil can hold it. Or the ground side of that circuit... I am just pulling hair out here trying to think this through.

 

[1maddog1]

k0ua, I appreciate your deep thought on this problem.....I have two meters, ones analog and the other digital, but they both will only measure up to 10amps DC... I could try to measure the current with the analog meter but most it will show is the pegging of the needle if there's more than 10amps. I don't think it will hurt an analog meter but it would certainly blow the digital one. Once again, as like you, I am scratching my head and a few other places and coming up empty!

 

[jamesrodneybookout]

i have the same problem the 12 volts to the pull the selonoid is not there where does the power to the relay come from ?