How to test B1700 ignition switch

tbronson · Jul 14, 2019

How do I check the B1700 ignition switch to see if it's working?

I've removed the switch, and unplugged the wires -- there are four flat copper leads that go into the plug. I have a multimeter.

Thanks!!

Dave_eng · Jul 15, 2019

I have attached the simple logic diagram for the switch.

In each of the 4 switch positions you need to have continuity between the terminals as shown.

Switch OFF: no continuity with any of the other terminals
Switch in ON position: continuity between 30 & AC
Switch in Preheat: 30, AC & 19
Switch in Start: 30, AC, 19, & 50

Why do you suspect the switch and what is the problem?

Dave

tbronson · Jul 15, 2019

It's totally dead in all positions. For a long time, starting has been uneven. Sometimes it turns over immediately, others, I have to turn the key a few times, or pull it out and reinsert -- I also reengage the clutch and jiggle the PTO levers, so can't be sure why it starts working when it does. Usually, lights on the dash go on and the fuel needle starts going up, but nothing happens in start, no click. Sometimes, more recently, nothing happens, no lights or needle. This time, it was completely dead and no amount of jiggling does anything.

I checked all the connections I could see: the battery and near the starter. Checked the PTO and 4WD levers are off and in position. Checked, actually, replaced the fuses.

Dave_eng · Jul 15, 2019

The most overlooked connection to check is where the ground cable attaches to the tractor engine or frame. This connection needs to be disconnected and all surfaces polished to bright metal.

This connection affects every circuit on your machine.

Do you know how to jump your starter?

It is a test to do when the engine wont turn over as it bypasses every safety switch. It needs to be done with great care, preferably with someone on the tractor with foot on the brake, as you can get run over by your own back tire.

I have attached a picture of a typical starter solenoid (removed from the starter for clarity purposes only) which has specific instructions.

If the starter alone does not work but other circuits power up then the mating face between the engine block and starter may be rusty. This is the starter's ground connection.

Dave

North Idaho Wolfman · Jul 15, 2019

tbronson said:
It's totally dead in all positions.

Are you checking the switch disconnected and with an Ohm meter or looking for power when it's still connected and powered?

The chart the Dave gave is for testing with it disconnect from power and the tractor.

If it's "totally dead" testing it with an ohm meter, you need a new switch!

tbronson · Jul 15, 2019

I'm testing with the switch removed. And I'll check the ground connection. Will report back after that.

Thanks!

tbronson · Jul 15, 2019

Tested disconnected switch with multimeter set to Continuity.

Four leads in plug socket with wire colors:

(1) red
(2) black / white stripe
(3) red / white stripe
(4) black / red stripe

Results

OFF nothing
RUN 1-3
PREHEAT 1-3-4
START 1-2-3-4

I checked in pairs so that means touching any two leads in the chart got a tone.

Does that mean the switch is fine?

AND:

Jumpstarted it with a screwdriver. Started up fine.

Dave_eng · Jul 15, 2019

The multimeter test of the switch looks good. It is possible the switch performs differently under a large current but for now assume it is good..

The jump start narrows down the problems.

Use your multi meter connected to the small solenoid terminal and to ground while you turn key to start. Lets see if you are sending 12 volts to the starter solenoid. Sometimes safety switches get corroded and, although they would test OK with a multi meter, when called upon to deliver a large amp draw to the starter solenoid their internal resistance is such that the solenoid does not get enough power to pull in.

Dave

tbronson · Jul 15, 2019

Dave_eng said:
Use your multi meter connected to the small solenoid terminal and to ground

Dave

What do you mean, "connect to ground"? (I'm not stupid, just ignorant. I learn pretty quick!

twomany · Jul 15, 2019

Just to be semantic.

It's a starter switch. After all, it is a compression ignition engine that needs no "switch" to run .

Fordtech86 · Jul 15, 2019

tbronson said:
What do you mean, "connect to ground"? (I'm not stupid, just ignorant. I learn pretty quick!

One lead of your meter to the small terminal on the starter and the other lead to ground (either the ground cable on the battery or a clean spot on the frame)

Russell King · Jul 15, 2019

And measure volts (greater than 12) DC. Don’t think about continuity or ohms here.

Sent from my iPad using Tapatalk

tbronson · Jul 16, 2019

Will check 12V at solenoid soon, no-one around and don't have alligator clips to do solo.

QUESTION: I can easily jumpstart it, but as soon as I remove the screwdriver, it immediately runs down and stops. Same when switch is at Off and at Run. How can I get it to keep running?

D2Cat · Jul 16, 2019

Sounds like the run side of your solenoid is not getting voltage, so it can stay running.

Not sure your tractor even has one, but many have a two stage fuel shut off solenoid. First stage lets the fuel flow, second stage lets it keep flowing, turn the power off and the engine quits.

Dave_eng · Jul 16, 2019

Let me start with a friendly suggestion for your next time..... instead of asking how to test the key switch, telling us about the symptoms you are trying to solve would be much more productive.

Do you have a WSM? If not send me a private message with your email address.

Your engine has a fuel cut off solenoid. In the absence of power through a 5 amp fuse, the engine gets no fuel so will not run or in other words the engine stops. This fuse gets its power from terminal AC on the key switch.

To keep the engine running after you jump the starter, the fuel cut off solenoid on the injection pump needs 12 volt power.
.
Buying a 12 volt test light for $10 will make your troubleshooting much easier than with a multi meter
https://www.amazon.com/Voltage-Cont...t&qid=1563304495&s=gateway&sr=8-1-spons&psc=1

Spending $23 gets you a test light with built in volt meter.
https://www.amazon.com/Jastool-Exte...t&qid=1563304611&s=gateway&sr=8-2-spons&psc=1

Dave

tbronson · Jul 16, 2019

I'll get a tester and test the solenoid.

Meanwhile, is there a practical way to jumpstart it and keep the engine running, getting around the fuel cutoff solenoid, so I can use the tractor while trying to fix it?

Dave_eng · Jul 16, 2019

I started by writing instructions on how to power the solenoid to keep the engine running but then became concerned you could easily power the pull in coil in the solenoid all the time the engine is running and burn it out.

Check the 5 amp fuse before we go any further.

Dave

tbronson · Jul 16, 2019

Dave_eng said:
Check the 5 amp fuse before we go any further.

Dave

Is this one of the four fuses in the fuse box? I checked those, none appear to be blown, but I will check them again with the meter. If not, where is the fuel shutoff solenoid fuse located?

Dave_eng · Jul 17, 2019

tbronson said:
Is this one of the four fuses in the fuse box? I checked those, none appear to be blown, but I will check them again with the meter. If not, where is the fuel shutoff solenoid fuse located?

I cannot tell where it is from the wiring diagram but likely in the main fuse box. I think there are two 5 amp fuses, one of which is for the stop solenoid.

Dave

tbronson · Jul 18, 2019

Rained out yesterday, but got a voltage tester.

Fuse box - 4 fuses
(all good, multimeter test)

KEY STOP 5A
HEADLIGHT INSTRUMENT CLUSTER 10A
WORK LIGHT 15A
HAZARD 5A

----
Tested small tab on starter, multimeter and voltage tester, key at start:

0.00 voltage, no light

How to test B1700 ignition switch

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