G1800 Electrical Problem

[EquipmentUser]

The problem is with the fuel shutoff solenoid fluttering when the engine is running. It is picking up voltage from somewhere as it is only supposed to be energized for a few seconds when the key is shut off. I have verified this problem with a meter, unplug it and it stops fluttering. I am leaning towards the combination box, the plastic cover was busted and the box was hanging by the wires when I picked this unit up.

I know that is where the shutoff solenoid wire comes from and I have checked continuity between it and all other wires in the harness to make sure it wasn't shorted in the harness somewhere and its not. Is there a way of testing the combination box? It looks like an expensive piece.

 

[jinman]

From my experience, the ignition switch is more likely to be your problem than the combo box. Make sure that your switch does not have dirty contacts and is losing contact due to vibration. If that happens, it could cause the cutoff solenoid to go into its shutdown cycle. I'd check the switch to see if it was the source rather than the combo box. My switch was so bad I had to install a special starter button because the start position did not work. In my case, someone disconnected the shutoff solenoid and I kill my engine with a pull knob that shuts off the fuel.

 

[EquipmentUser]

I worked on it a little more today, the combination box is definately the cause. I can take it and beat it against the frame and the solenoid will stop fluttering. The wiring connection is good. I checked my switch with a meter and it is working fine, even disconnected it and used a jumper wire to rule it out.

On a side note, I have no idea how old this little tractor is, what years were the G1800's made?

 

[Craig Clayton]

I guess you are right sometimes that is the correct method for working on delicate electronic control boxes. Beat them and check for smoke. If you were to add a bit of resistance to the wire that goes to the fuel solenoid it might reduce the voltage to low enough that the solenoid will not try to cycle ( chatter ) .The rule of thumb is coils drop out at 80% of rated voltage and pull in at 90%. The voltage to the coil maybe 14.6 VDC
( 12 V) or it could be something lower. I am trying to think of a inline resistor than will not draw much current and only drop the voltage maybe 4 VDC. A old style reostat but I am not sure what reistance to set it to. On the old ignition systems there was a ballast resistor I think that would be about the right value. I have not done the math but I think that is about right.
Craig Clayton

 

[jinman]

I guess you are right sometimes that is the correct method for working on delicate electronic control boxes. Beat them and check for smoke. If you were to add a bit of resistance to the wire that goes to the fuel solenoid it might reduce the voltage to low enough that the solenoid will not try to cycle ( chatter ) .

Craig, do you know how this circuit works? From your description, it would seem that you do not. EquipmentUser's method is perfect for the symptoms. His problem is NOT a solenoid, but rather the circuit that operates it.

If you'd like to know, when the key is shut off, the combination box sends a signal to the solenoid for 10 seconds to energize it and shutoff fuel to the injector pump. If there is a bad connection within the box or the ignition switch is noisy, the combo box falsely thinks it should send out it's signal. By giving the box a rap, EquipmentUser simulated the same kinds of vibration felt during operation.:thumbsup:

EquipmentUser, I don't have the data in front of me, but I think the G1800 was built between 1994 and 1999.

 

[Craig Clayton]

To jinman
I could be wrong but in reading the quote ( The problem is with the fuel shutoff solenoid fluttering when the engine is running. It is picking up voltage from somewhere as it is only supposed to be energized for a few seconds when the key is shut off.) I drew the above thoughts.
I suggested he put a resistor inline with the wire that goes to the solenoid because it is quote ( picking up voltage from ) . This stray voltage is causing the solenoid to quote (
fluttering ) . The combination box must have some problem of which is expensive to repair. If we can keep the leakage voltage below a certain threshold then the solenoid will not flutter when the tractor is running.
The idea of the old style ballast resistor on Dodge coils was to start the vehicle on 12 V because the starter pulled the system down but when the charging was at 14.4 V it did not put full voltage to the coil. I have lost ballast resistors and driven home by jumping around them but it was known that the coil could not stand charging voltage.
If the switch component in the combination bow is a transistor it could be leaking through some voltage. I just went through this with a major supplier of a component and when I talked to the engineering dept they said ( go away you are wrong ).My boss called months later the same engineering rep and was told it can not be. We sent a unit to them and for the first 2 weeks the emails said we were wrong about leakage voltage. Then they Emailed and admitted that they had found the back transistor. We still have a pile of bad units in service and failing.
Craig Clayton

 

[EquipmentUser]

Well I installed the new combination box. I can't say that it fixed my problem but there's a definite difference now. The glow plug light works now, the fuel guage works now, and when I turn the key on there is an audible continuous clicking sound coming from the box, is this normal? The old one did not do this.

I still have the solenoid flutter, doesn't seem to be as bad though so again I disconnected the ignition switch and used a jumper wire in the connector to simulate "key on" and still had flutter. At this point i'm thinking its a wiring harness issue because there's really nothing left. I bypassed all the safety switches except the brake switch because its hard to get to, guess i'll have to fight it to rule it out. I'm gonna get my meter and spoon in to the connector coming off the combination box so I can see if its actually sending out the voltage fluctuation or not. I may have to try to wire in a resistor, i'm sure that would work, I just don't know what size I would need. Any ideas?

 

[jinman]

If you wire a resistor in series with the solenoid, you will do nothing but drop current in the circuit and may inhibit the solenoid from operating at all. You could add a capacitor in parallel to filter out unwanted spikes from the combo box also, but that can get complicated too. The easiest fix for your problem is to wire 12 vdc to a momentary contact kill switch to the solenoid and remove it's input from the combo box. If you think the combo box is putting out the proper kill signal when the key is turned off. You could put a normally open momentary switch in series with the line to the solenoid from the combo box. Then, when you get ready to kill the engine, just press on the momentary switch and turn off the key. Hold the switch until the engine dies and release it. It's like wearing a belt and suspenders.:thumbsup:

 

[lakeside]

I bought my G1800 used in 1995 with 165 hours on the clock. The salesman said the unit was two years old which matches the clock. So I'd say the G1800 goes back to at least 1993.

Great machine, but the solenoid did go south after a year. Rather that fiddle around I disconnected the solenoid arm and installed a manual shut-off. Works like a charm. I remember what an old mechanic told me: What ain't there can't break. :thumbsup:

 

[jinman]

I bought my G1800 used in 1995 with 165 hours on the clock. The salesman said the unit was two years old which matches the clock. So I'd say the G1800 goes back to at least 1993.

I just looked at my maintenance manual and it shows a publication date of 1989/1990, so they may have been sold as early as then.