No Starter Action on M4700

GeoHorn

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Got a ‘96 M4700. The only safety start switches are on the Range Lever and the PTO Lever.

The Key has 4 positions: Left = Glow Plug Warm-Up, OFF, Run, and Start.

Occasionally (dammit...it’s intermittent).... I turn the key to start and NO ROTATE of the starter... BUT...I installed an Ammeter and it displays a 40 Amp DisCharge!

This just so happens to be the exact same Discharge (40A) which the Glow Plug warm-up draws.

Sometimes it rotates/starts normally. Sometimes just the discharge indication.

I have wiggled the range lever... wiggled the PTO lever.... still intermittent.... Sometimes it rotates the starter...sometimes it doesn’t.

But the puzzle to me is.... WHY does it show a DISCHARGE even when the starter is not activated... AND... even if I deliberately put the Range Lever and/or the PTO Lever in a “no start” position. This leads me to believe it MAY be one of those switches.... EXCEPT for the fact of that 40 A DIScharge EACH TIME.

Do the Glow Plugs always power up even on a normal start?

Addt’l clue: Even when the starter rotates.... it’s still only (approximately) a 40A Discharge indication ...but he needle “wiggles” when the starter rotates... does NOT wiggle when the starter does not rotate.

I’m gonna get into the schematics, but thought I’d hope one of you guys might have an idea. (And, do the glow plugs operate automatically even on normal starts?_
 

Russell King

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On my L185 the glow plugs are energized in both positions. I am pretty sure that your’s will be active in both positions.
 

Roadworthy

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Forty amps sounds about right for the glow plugs. If the starter energized the current would be MUCH higher but the ammeter may be wired such that starter current doesn't flow through it due to the greater current flow. It is possible you are not activating the starter relay or solenoid due to a defective contact within the ignition switch, a defective solenoid, or even a poor connection somewhere.
 

Dave_eng

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Glow plugs need to be powered during cranking. On older tractors like the L185, during pre-heat, power flows through the glow indicator on the way to the glow plugs.

When the key is turned to the START position, the glow indicator is bypassed but current flows to the glow plugs.

Concerning the starting problems, a simple test to do is to check for the presence of voltage at the starter solenoid (disconnect the solenoid trigger wire) when the key is turned to START. Test the end of the wire removed from the solenoid.

A 12 volt test light is the cheap tool to use.

Safety switches get tired. They will conduct some power but often not enough to engage the solenoid.

If you see power at the solenoid end of the trigger wire, then the relay fix described in the link below can be your answer to reliable starts.

The power needed to trigger a relay is much less than the power needed to engage the starter solenoid.

The relay is triggered and it in turn directs a strong power signal to the starter solenoid.

Starter relay kit

Dave
 

GeoHorn

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Hmmmn... Thanks for those inputs.
Of course, I guess it could also be a dying starter-motor also... I’ll clean those starter contacts and test for voltage at the starter terminal tomorrow.
 

GeoHorn

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Hmmmn... Thanks for those inputs.
Of course, I guess it could also be a dying starter-motor also... I’ll clean those starter contacts and test for voltage at the starter terminal tomorrow.
Well... The intermittent nature of this is troublesome for diagnosis. There is power avail at the solenoid terminal (blade).... but the starter is also operating normally at each attempt also.
It’s difficult to “fix” it if it’s not broken during tests. Grrr.

Each time it (starter) DOES fail to rotate with the key.... at the next key-turn or two it returns to normal operation. If it‘d fail and stay that way it would be easier to diagnose.
 
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GeoHorn

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Adding the relay now will help, if not now, at some future date.

It will not make things worse!

Dave
Dave, I don’t see how inserting an addt’l relay Into the circuit will be helpful except to add another failure possibility. (It doesn’t remove any item that might be intermittent..so the intermittent issue will continue.)
I don’t want to disable my safety switches. If they are bad then I’ll replace them.
If the key switch is bad I’ll replace it.
It’s just difficult to identify the intermittent failure until it becomes continuous.
Thanks for the suggestion, however.

(BTW: Beware of the link provided to the starter relay, as it has a trojan within it Supposedly attempting to sell anti-virus software.)
For those interested in the relay schematics, here they are:
 

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Dave_eng

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Dave, I don’t see how inserting an addt’l relay Into the circuit will be helpful except to add another failure possibility. (It doesn’t remove any item that might be intermittent..so the intermittent issue will continue.)
I don’t want to disable my safety switches. If they are bad then I’ll replace them.
If the key switch is bad I’ll replace it.
It’s just difficult to identify the intermittent failure until it becomes continuous.
Thanks for the suggestion, however.

(BTW: Beware of the link provided to the starter relay, as it has a trojan within it Supposedly attempting to sell anti-virus software.)
For those interested in the relay schematics, here they are:
The logic behind the addition of the relay has been recognized by Kubota and other manufacturers who now build the start relay into their design. They realize that trying to power a starter solenoid can prove to be too onerous a task for simple safety switches over the useful life of the tractor

By using the suggested relay you are not disabling safety switches but rather keeping them in operation where some owners start to jump them as they give problems.

Your initial post contained a question about the 40 amp load even when the key is in the start position and the engine is not cranking.

I pointed out that the design is for the GP's to be powered during the Start cycle.

If you are doubtful about the usefulness of the suggested relay, wire up a simple light which will come on when power is sent to the starter solenoid. Make the + connection at the starter solenoid end of the circuit. An LED will do the job and not draw down any voltage present.

Now each time the intermittent start situation occurs you can see if power is being sent to the starter solenoid even if it does not engage.

I have provided the same link to about a dozen people and no one has had any issues with it. I tried it myself just now and it worked quickly and without anything strange happening.

I looked at the two wiring schematics you provided. While the general wiring concept is correct, the type of starter system that benefits from the relay I have suggested is one where the solenoid is part of the starter and which has as one of its functions to pull the starter drive gear into engagement with the flywheel. in the design shown in your schematics, the starter engages the flywheel by spinning the gear forward so the solenoid needs far less power to be activated.

Dave
 
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GeoHorn

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OK...here’s an update: It turns out hat Kubota ALREADY HAS a starter-relay in the circuit, essentially exactly as Dave-Eng ‘s suggested solution.... so there’s no advantage to doubling that.

The way I discovered it was the tractor finally failed to start enough to allow me to take some readings with a VOM. Here’s what I’ve discovered... just Still haven’t soved the problem:

Opening up the dash, I checked the key-switch to determine the start-position-terminal delivers 10 volts. Thinking this key-switch must have internal resistance and I’ve found the problem.... I bypass the key switch and the starter still does not operate. This indicates the key switch is not the problem.

I remove the starter and open it up and the starter solenoid contacts are slightly burned so I clean the contacts with a wire brush and the starter operates reliably. This removes the starter as the problem.

Further testing with everything re-assembled demonstrates the starter is still inoperative.

I look behind the panel and there are a number of relays. One is the Hazard flasher, another the Glow-Plug relay, another yet to be determined...but one is a starter relay. I’ve unplugged the starter relay and jumpered across the terminals which supply power to the starter-solenoid and the starter activates. This leads me to believe the starter-relay must be bad. I removed it and pried it open and it’s clean inside. I supply power to it and it operates reliably and the secondary circuit reliably conducts power across it’s terminals. I used a flat swiss file to clean the contacts despite the fact they appear in good shape. Using a VOM the relay tests fine. This seems to confrim the relay is not the problem.
I reinstall the starter relay and make many start attempts....and they all work just fine.

I am still at a loss to determine why the starter function is so intermittent. The only thing odd still existing is the key-switch which is a metal case with a bakelite backing which contains the terminals and presumeably the internal contacts. The VOM shows zero ohms internal resistance at each terminal despite the fact the bakelight backing-plate is slightly loose in the metal casing. There is no time that turning the key to start that the starter-relay terminal isn’t properly powered (although it reads only 10 volts. That is the same voltage at the starter solenoid which consistently activtes the starter.

It’s damn hard to fix something that won’t stay broken. Grrrr..
 

Dave_eng

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Using the VOM meter to assess the start switch can be misleading. I know it is the WSM testing procedure.

As was discussed before you determined your tractor already has a start relay, the circuit to pull in the starter solenoid uses considerable amps.

If you are reading 10 volts at the key switch, something is not correct as the switch should show battery voltage in the start position.

Disconnect the GP relay and test the starter solenoid voltage to see if it is now at battery voltage.

Dave
 
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dvcochran

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OK...here’s an update: It turns out hat Kubota ALREADY HAS a starter-relay in the circuit, essentially exactly as Dave-Eng ‘s suggested solution.... so there’s no advantage to doubling that.

The way I discovered it was the tractor finally failed to start enough to allow me to take some readings with a VOM. Here’s what I’ve discovered... just Still haven’t soved the problem:

Opening up the dash, I checked the key-switch to determine the start-position-terminal delivers 10 volts. Thinking this key-switch must have internal resistance and I’ve found the problem.... I bypass the key switch and the starter still does not operate. This indicates the key switch is not the problem.

I remove the starter and open it up and the starter solenoid contacts are slightly burned so I clean the contacts with a wire brush and the starter operates reliably. This removes the starter as the problem.

Further testing with everything re-assembled demonstrates the starter is still inoperative.

I look behind the panel and there are a number of relays. One is the Hazard flasher, another the Glow-Plug relay, another yet to be determined...but one is a starter relay. I’ve unplugged the starter relay and jumpered across the terminals which supply power to the starter-solenoid and the starter activates. This leads me to believe the starter-relay must be bad. I removed it and pried it open and it’s clean inside. I supply power to it and it operates reliably and the secondary circuit reliably conducts power across it’s terminals. I used a flat swiss file to clean the contacts despite the fact they appear in good shape. Using a VOM the relay tests fine. This seems to confrim the relay is not the problem.
I reinstall the starter relay and make many start attempts....and they all work just fine.

I am still at a loss to determine why the starter function is so intermittent. The only thing odd still existing is the key-switch which is a metal case with a bakelite backing which contains the terminals and presumeably the internal contacts. The VOM shows zero ohms internal resistance at each terminal despite the fact the bakelight backing-plate is slightly loose in the metal casing. There is no time that turning the key to start that the starter-relay terminal isn’t properly powered (although it reads only 10 volts. That is the same voltage at the starter solenoid which consistently activtes the starter.

It’s damn hard to fix something that won’t stay broken. Grrrr..
I agree, it is difficult to trace a problem when it is erratic. I would say some of your test procedures may not be conclusive. For example, when you remove the starter there is more to check than just the connections and contacts. The solenoid coil could be getting weak, causing 10 volts to be a 'threshold' where it may or may not work (10.1 volts vs. 10.9 volts). The brushes, armature or windings inside the starter could be going. When you removed and checked the relay I do not remember you mentioning the relay socket and connections.
Conventional circuit troubleshooting, especially when it is erratic, requires Each component and break in the circuit wiring be tested and proven good. This can take time. So if you use 12 volts as the baseline for a pass, 10 volts After the switch is actuated is the starting point of a failure. That may not be the Only problem (which exacerbates the problem) but it is a starting point.
My suggestion would be this: since you can activate the glow plugs separate from the starting circuit, use a simple starter push button, available at most part stores, and jump around everything and wire straight to the starter solenoid.
!!!Remember!!! The safety's will also be jumped around!!!
Make sure everything is taped up and safe to run that way for a while. To cold start, fire the glow plugs a bit and then start from the added pushbutton. This will prove out the starter and solenoid and narrow the search down to the switch (which I suspect) and/or the relay/base OR wiring.
If it is easy to access you could move the temporary wire to the +coil wire on the relay and prove it out in the same fashion.
Not fully conclusive but a good test on the wiring is to check for base voltage at each connection; remove the solenoid wire, apply 12 volts on the circuit, clamp your meter to the solenoid wire so you can see the display and start giggling wires around at each connection and joint looking for changes in voltage. You could have a bad termination or a wire breaking down enough that 10 volts apparent is not enough every time.
As an aside, I assume you have 12.xxx volts at the battery?
 

GeoHorn

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Dvcochran, Thank you... yes, meticulous and methodical troubleshooting is important.
I actually have a mechanic’s starter-switch I bought from the Snap On man when I worked as a Toyota Tech in the early ‘70s... that’s a good suggestion.... IF THE DAMN THING WOUJLD STAY FAILED! The starter has been doing fine each attempt since my last entry.
I am puzzled over that 10 volts as well, and I know it’s not right. I’ve allowed myself to slip into “assume” mode I think...because I’ve been willing to accept it as the draw-down from the GPs. I will remove the GPs from the start sequence ...NEXT TIME it presents a failure-mode.

IN another thread, Russell King wrote: “
Geohorn,
Starter fixed or just the lucky day the starter works?
I have not seen the conclusion of that saga yet!”

Welll....... all I can say is... it’s intermittent and presently stuck in “work every attempt” mode. I wish it’d fail and stay failed so I can get it diagnosed. Thx for staying on it with me.
 

torch

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If you are reading 10 volts at the key switch, something is not correct as the switch should show battery voltage in the start position.
^^^^^This.

The relay will hold at 8 or 10 volts, but that may not be enough to pull it in -- which could explain the intermittent nature of the problem. You need full battery voltage (+/- 12.5v) at the relay coil when the key is first turned to start. The starter does not engage until the relay pulls in, so 10v while the starter is cranking should not affect things.

As others have said, the glow plugs are powered while cranking, which explains your 40 amp draw. The starter motor draws hundreds of amps and is not fed through the ammeter. The fluctuation you see when the starter is cranking is due to the drop in battery voltage, which affects the current drawn by other circuits (Ohms law: Current = Resistance / Voltage).