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fuelshutoff selenoid overheats

raul All ground wires are good. How do you test selenoid?
Dale Raul: Are you speaking about a Rossa Master injection pump solenoid in the pump or a screw in type? Either way I am questioning how you are establishing the solenoid is actually over-heating.

Nonetheless there is one terminal and the body of the solenoid coil is another. First set your meter on volts dc 20 scale if you have a 12Vdc electrical system. Install one probe on the meter to the terminal and the other to the base or ground and read the voltage as the switch is on as the machine is running. It should not be higher that the battery voltage because an alternator overcharging will cause the voltage to rise and overheat the solenoid valve.

If your voltage while running is 12Vdc to 14vdc it's ok to proceed with the resistance test, the ohm scale on the meter and again touch the terminal and the base with the meter leads and read the ohms scale reading. If the coil in the solenoid has lower resistance than it should it will draw more current which results in heat.

Either way I would be interested in how you have determined the coil is overheating but is still working? You should run a temp gun on the injection pump housing as well as the solenoid to make sure the coil is not getting hot from some other heating like conduction.

raul Dale ,How can I test the fuel shut off selenoid ?
Dale Use a digital volt ohm meter and set it on the ohms scale. The fuel solenoid is usually grounded at the case and has one wire insulated.

See what the ohms are on the meter and calculate current draw by those figures of ohms and applied voltage from the system.

If you have a 12Vdc system and a good 12 Vdc battery and the ohms read 48 you divide the volts 12 / by the ohms. Getting hot is different than not operating with an open circuit. If the solenoid has an open circuit then it will remain cool and not operate.

Your case is it is heating up and working I interpret. So if you have 12Vdc and 12 ohms the current draw is one amp and that would surely heat up the solenoid. There is an ohm rating on the coil (fuel shutoff) it is in the JD specification and testing manual but I can tell you from experience the coil should have around 35 to 50 ohms or more with 48 ohms the coil would draw around 250 milli amps which is 1/4 of one amp. So check the resistance if possible with a meter on the fuel shutoff solenoid.

The other way is to disconnect the wire on the solenoid and turn on the switch to energize the fuel shutoff solenoid input wire. Lightly touch the wire end to the solenoid input terminal and watch for a blue flash, if you have quite a bit of experience at testing those in the shop you can tell right away without the meter if they are shorted internally. A flash from a quarter amp is way smaller that that of 1 amp. but you need to have tested many in the shop before relying on that method.

raul Dale thank you for response. Yes it works but gets very hot in 10 min. I have continuity from blk to wht and red wires. From blk to wht 0.4 ohms from blk to red 4.5 ohms. Per tech manual pull in is good 50 amps for 1 sec and drops to zero. Hold in should be 1 amp but is 2.5 amps continuous. Any thoughts?
Dale Raul: Sounds like a 455 or like compact tractor. Applied voltage is directly proportional to gauss in magnetic strength. So the solenoid that is said to draw 1 amp and is drawing 2.5 is way off. If I knew the tractor you were working on I could help more I think. Important is that the pull in should draw no more than the continuity in ohms of that coil circuit.

To cause more current to flow the voltage can be raised or the ohms resistance could be lowered. In specific the ohms in the book for the machine should be read for the coils. What machine are you working on?

raul Sorry dale. Should have said so.My tractor is a 970. My tech manual makes no reference to the fsos ohms. In repair specifications for electrical system says use CTM-3. Don't have. Have replaced TDCM, SEAT SAFETY SWITCH, IGNITION SWITCH, AND VOLTAGE REGULATOR. tomorrow I will pick up a new fsos.
Dale Raul: If you have the access to a Lowes or something like that they sell the infrared temperature guns for 20 - 30 $. Then you could shoot your temp at the solenoid. I have had those get hot also when someone wires around the start circuit and tries to hold in the coil with the pull in coil. Important is that where the electrical connection is that comes from the relays is not getting hot.

You mentioned, seat switch, ignition switch, and voltage regulator but what is the TDCM I am not familiar with that one. None of those will overheat the fuel shutoff solenoid coil but they would prevent it from pulling in.

When the tractor key is turned on to the on position does the pull in solenoid coil for the fuel shutoff pull in and does it hold in while the tractor is running? It is important to make sure the coil is actually getting to hot by a specific number in degrees. My only question right now would be how fast does it get to what temperature? Is it smelling hot also or just getting warm? 2.5 amps is about a 1157 bulb with the taillight filament and the stop light filament burning at the same time so that's just to relate with the ohms resistance in the bulb.

Are you using a volt ohm meter to check continuity? That fuel shutoff solenoid will have a four or five wire connector instead of a one wire. The only way to prevent that overheat would be to replace that solenoid but it will go out eventually if it is overheating. The only way that could happen like I said before is more than system voltage which is easy to read with a 15 dollar volt ohm meter on the input side and then if the coil wire insulation has overheated the resistance will be lower than specified. A modern gear reduction starter on a small engine like 4 cylinder draws around 50 to 75 amps and that's huge compared to your small fuel shutoff solenoid. I will look up the information if you don't have the service book. I have the CD for the compact utility tractors that have that same type of fuel shutoff solenoid.

raul Dale. My bad. After fuel shutoff solenoid (fsos) quit I did bypass by using wire to pull n hold the hold in coil while I unloaded shredder from trailer n moved in to shop for repairs. 30 mins tops.
Under JD shop mechanic advice the first thing I checked was the time delay control module (tdmc). Check for burnt components. Removed back cover n found lower right corner of circuit boardvery dark with 3 large resistors that showed they had been getting excessively hot. Replaced tdcm. Fsos still getting hot.
As per manual instructions I started testing steps. Seat safety. switch n ignition switch n fsos relay passed 1/2 the tests n failed the other 1/2. Replaced parts just to make sure. Strangely the new parts gave the same readings as the old. Fsos has only 3 wires /blk/grnd , wht/pull in, red/hold in. Test results. Blk to fsos body no continuity. Blk to wht n blk to red continuity on old n new fsos. Old n new fsos blk to white .4 ohm. Old fsos blk to red 4.5 ohms... New fsos blk to red 12 ohms. White wire readings good 50 amps/batt volt.age for .5 to 1.5 sec. And down to zero. Red wire now reads .7 to .8 amps. 1 amp max allowed according to manual . still gets very hot in 10 mins of tractor running. By hot I mean cannot touch for more than 2 secs. I'm not a wuz I'm a welder use to hot metal. New fsos part # AM 882277.
Yes using good multi meter n borrowed a better one. A clamp on meter. Have compared readings . both are very close if not the same.
Half ways thru found alternator connectors with signs of getting very hot. Dark white connector slightly melted wire insulation at alternator end n voltage regulator end. Signs of some contact between both wires . Have replaced with new connectors. Voltage regulator also was getting very hot. Replaced VR too. BOTH FSOS AND VR ARE STOLL GETTING HOT

raul Dale. Checked temperature. In 10 min up to 106 to 110 degree. Ran tractor at about 1200 rpms for 30 mins . max temp 130 degrees as I got thermometer closer to engine bloc . I sure thought it was hotter than that. Good ..news.... Because off voltage regulator and a white/red wire getting hot I disconnected the two wires coming from the alternator and neither the wire nor the voltage reg got hot. Will check wire harness. Ur thoughts ?
Dale I did the same thing on a GX355, same type of set up but I fried the relay somehow on the control circuit board. Anyway the three wire coil sounds like a simple dual coil. Did you check resistance on both the pull in and the hold coil? Possibly one wire goes to ground and the other coil is wired in parallel and when the coil is energized to pull in the hold in coil is actually energized also. Anyway the 1 amp or less seems very normal.

As the switch is turned to the on position put one meter lead wire to ground and then touch each fuel shutoff solenoid wire with the other lead of the meter and then sit on the seat or put something heavy on it and do the test again when you hear the solenoid pull back. Start the engine and measure the voltages again at the solenoid connector on the engine. Note those tests down and then measure the voltage at the battery. The only way something like a solenoid get's to hot or hotter than designed is when more voltage is applied than the coil was designed to handle on a steady basis.

As the voltage rises so does the current flowing into the coil. If the coil gets to hot then the insulation on the wire melts and then reduces coil resistance. The wires and terminals overheated is a sure sign but for fact the resistance is critical. What if both coils are running at the same time, the voltage test will reveal that. This is an interesting problem and I wonder what the normal running temperature of the hold coil is? Need to run a temp gun check.



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