What damage can repeated Jump Starting cause?

[TheOldHokie]

according to the diagram in the WSM, page 384, the 'starter relay'( 4) has a 5 amp fuse, the starter has a 40 amp fuse (6). The starter relay contacts feed the 12v to the starter.
So, if he's replacing the starter relay contacts ,he needs a switch that will carry 40 amps.
If he's bypassing allt eh 'safety stuff' and controlling the starter relay coil, then the switch needs to handle 5 amps (rating of fuse (5) ).

I think his intent is to simply put a pushbutton across the starter solenoid and battery. That switch has to handle the current draw of the solenoid and nothing else.

A typical starter solenoid design uses two coils - a pick coil that draws something like 20-25 amps and a hold coil that draws something in the 10 amp range. When initially energized both coils are in the circuit and you get a combined current draw of 30-40 amps for a matter of a few milliseconds. Then the pick coil is effectively shorted out and the hold current settles at around 10A. You can use a relatively light duty pushbutton switch but the solenoid design is hard on the contacts and switch lifetime will be reduced. Thats a pretty common issue in older vehicles where the solenoid was switched directly by contacts in the key switch.

Starter motor inrush current is several hundred amps and steady state cranking current north of 100. The motors are not fused.

Dan

 

[Sparty047]

Well, Okay then!

By reviewing all responses (thank yous to each respondant) it looks like a "go" to me.

I am going to put all the wiring bundles back together, secure the fuse block, and wire a simple "engine start push button momentary start switch" to replace the starter relay.

BTW: Doing this does NOT bypass any of the safety relays. Driver must be seated with foot on the clutch and PTO turned off. Switch main to preheat as needed; switch to start; push the engine start to engage starter; release button when deisel starts. Since this is an HST, I may consider a bypass of the seat switch, so I can leave the tractor idling and climb down. Right now when I stand the engine stops.

Thanks again.

 

[SDT]

Dad, had a 47 Chevy sedan when I was a kid. I was kinda young but IIRC that big starting pedal did 2 things. It engaged the flywheel and had a large momentary contact switch to turn on the motor. Then he got a REALLY modern car. A 1950 Pontiac. Wonder of wonders it had a little chrome starter button on the dash. Coolest thing ever. Then for years everything was done by the key. Now? We're back to pushing a button. Will wonders never cease? LOL

First car at age of about 12 was a 47 Pontiac with similar starting system as did just about all of the era. With a bit of practice it was possible to push the starter pedal with toe while pumping the accelerator pedal with ones heel at the same time. Father once had a 1950 Buick with starter switch beneath the accelerator pedal. Pushing the accelerator pedal hard to the floor engaged the starter if the key switch was in Start rather than Run.

 

[BruceP]

What risk of damage do I run if I completely remove the starter relay switch and just add an Engine Start Push Button wired into the starter relay harness?

No risk of damage to machine.
HOWEVER: DO NOT GET COMPLACENT using this method to crank engine. Many folks have been killed by starting tractor engine and getting run over by the machine.
There are reasons the safety switches exist to ensure someone is in the seat when engine is cranked.

You can add a simple helper relay.

This is EXACTLY what I did on my machine. Now, the lower-voltage only has to pick the helper-relay. The new relay sends FULL battery voltage to the bendix solenoid.

 

[BruceP]

BTW: Doing this does NOT bypass any of the safety relays. Driver must be seated with foot on the clutch and PTO turned off. Switch main to preheat as needed; switch to start; push the engine start to engage starter; release button when deisel starts. Since this is an HST, I may consider a bypass of the seat switch, so I can leave the tractor idling and climb down. Right now when I stand the engine stops.

I just saw this AFTER my last post

If you are simply adding a button to bypass the contacts within the keyswitch.... NO PROBLEM. Just use a high-quality, weatherproof button.

Many folks choose to use one of those milatary-grade, Catterpillar-style, starter switches. (1/4 turn lever thingy) https://cdn.shopify.com/s/files/1/0254/6447/1632/products/41nkmcNRE3L._AC_800x.jpg?v=1616464934

 

[TheOldHokie]

I just saw this AFTER my last post

If you are simply adding a button to bypass the contacts within the keyswitch.... NO PROBLEM. Just use a high-quality, weatherproof button.

Many folks choose to use one of those milatary-grade, Catterpillar-style, starter switches. (1/4 turn lever thingy) https://cdn.shopify.com/s/files/1/0254/6447/1632/products/41nkmcNRE3L._AC_800x.jpg?v=1616464934

Well, Okay then!

By reviewing all responses (thank yous to each respondant) it looks like a "go" to me.

I am going to put all the wiring bundles back together, secure the fuse block, and wire a simple "engine start push button momentary start switch" to replace the starter relay.

BTW: Doing this does NOT bypass any of the safety relays. Driver must be seated with foot on the clutch and PTO turned off. Switch main to preheat as needed; switch to start; push the engine start to engage starter; release button when deisel starts. Since this is an HST, I may consider a bypass of the seat switch, so I can leave the tractor idling and climb down. Right now when I stand the engine stops.

Thanks again.

Yes but. It does bypass any cranking interlock.

Dan

 

[GreensvilleJay]

re: ...
wire a simple "engine start push button momentary start switch" to replace the starter relay.

BTW: Doing this does NOT bypass any of the safety relays.

YES it does ! Your push button replacing the starter relay contacts does in fact bypass all the safety switches that are in series with the starter relay.

perhaps you can 'cut and paste' a modified version of the wiring diagram. Maybe something is 'lost' in the wording.....

 

[BruceP]

I am going to put all the wiring bundles back together, secure the fuse block, and wire a simple "engine start push button momentary start switch" to replace the starter relay.

Just EXACTLY what are you trying to do?

Now I am confused.... your tractor has a "starter relay" ????

Most engines which use a bendix type of starter has a relay built into the starter.
Does your starter have ONE BIG WIRE... or also have a small 'signal' wire to initiate starting?

Explain again why you do not simply FIX the problem instead of rewiring the starting system?

Using VOLTAGE DROP TESTING should take no more than 10 minutes to isolate the problem. At that point, your only issue would be to decide HOW to fix it.

 

[07wingnut]

I wired these in for emergency use only, if I experience a failure of the safety switches. It allows me to go when there is a problem, get the job done, and then worry about fixing the safety switch problem. The toggle is a safety bypass for ALL the safety switches, and the push button is a start any time the key switch is on. Not many people want to be playing with their safety switch continuity when there is a job to be done under time constraints.


I have front mount snowblower, and a dog that loves to deposit stones all over the driveway. Using the bypass switch, allows me to dismount and remove shear pin destroying stones, without shutting off the blower all the time. If this causes me to be injured, I guess I will just have to sue myself.

 

[Pau7220]

Now I am confused.... your tractor has a "starter relay" ????

Most engines which use a bendix type of starter has a relay built into the starter.
Does your starter have ONE BIG WIRE... or also have a small 'signal' wire to initiate starting?

Explain again why you do not simply FIX the problem instead of rewiring the starting system?

Using VOLTAGE DROP TESTING should take no more than 10 minutes to isolate the problem. At that point, your only issue would be to decide HOW to fix it.

You’re causing more confusion by calling a solenoid a relay. Relays are not built into starters. Relays have been added to many starting circuits because the wiring, switches, opc, etc. can’t supply enough current to operate the magnet in the solenoid on the starter.

Completely agree on the too often overlooked voltage drop test.

 

[Dave_eng]

The other system which is likely not being operated as designed with this dedicated switch is the glow plug's circuit.
The key switch logic diagram shows the GP's powered during engine cranking.
Not powering GP's during cranking will make starting much more prolonged during cold weather.
Dave

 

[TheOldHokie]

Just EXACTLY what are you trying to do?

Now I am confused.... your tractor has a "starter relay" ????

Most engines which use a bendix type of starter has a relay built into the starter.
Does your starter have ONE BIG WIRE... or also have a small 'signal' wire to initiate starting?

Explain again why you do not simply FIX the problem instead of rewiring the starting system?

Using VOLTAGE DROP TESTING should take no more than 10 minutes to isolate the problem. At that point, your only issue would be to decide HOW to fix it.

He does not have a bendix type starter.
He has a solenoid type starter.
The starter solenoid is energized via a starter relay in the key switch circuit. The motor is then switched by a second set if contacts (e.g. relay) inside the solenoid.

Dan

 

[shirleyujest]

What your asking is not "jump starting" it's just bypassing the electrical system.
Why don't you try replacing the starter relay, as that should be the cause of the voltage loss.

With a 1 volt drop between battery terminal to the starting relay it could a corroded battery cable. If both ends of cable are clean and not corroded, it could be the cable itself.

 

[DustyRusty]

He does not have a bendix type starter.
He has a solenoid type starter.
The starter solenoid is energized via a starter relay in the key switch circuit. The motor is then switched by a second set if contacts (e.g. relay) inside the solenoid.

Dan

The Bendix is the gear at the front of the starter. When the engine starts, the speed of the flywheel will spin the Bendix gear in a way that causes it to disengage. This prevents the starter from continuing to be engaged with the flywheel. The solenoid is either mounted on the top of the starter or nearby, and it transfers the power to the starter from the battery via the red battery cable.
One of the biggest problems is that many people have no idea what a particular part does or what the proper nomenclature is to describe it. A relay can be activated by either putting power to it or by grounding it, depending on the type of relay it is. The Bendix drive is not an electrical device, but a gear that is put in motion by the starter when it starts to spin, causing the Bendix drive to move forward into the flywheel starting the rotation of the engine.

 

[GreensvilleJay]

here's the wiring for his tractor...
I'm thinking he wants to replace the starter relay(4) contacts with a pushbutton.
Since the contacts have a 40A fuse, that is why I'm suggesting a 60A push button.
Rewired this way DOES bypass all the safety stuff...

 

[TheOldHokie]

The Bendix is the gear at the front of the starter. When the engine starts, the speed of the flywheel will spin the Bendix gear in a way that causes it to disengage. This prevents the starter from continuing to be engaged with the flywheel. The solenoid is either mounted on the top of the starter or nearby, and it transfers the power to the starter from the battery via the red battery cable.
One of the biggest problems is that many people have no idea what a particular part does or what the proper nomenclature is to describe it. A relay can be activated by either putting power to it or by grounding it, depending on the type of relay it is. The Bendix drive is not an electrical device, but a gear that is put in motion by the starter when it starts to spin, causing the Bendix drive to move forward into the flywheel starting the rotation of the engine.

We are confusing two different starter motor designs

A Bendix drive starter uses inertia and spiral grooves on the starter motor shaft to extend the pinion gear into the ring gear. Widely used up until the late 60s/early 70's. Motor current was switched with a big ass mechanical pushbutton (usually foot operated) or an external relay that was switched by contacts in the rotary. key swith. i have three such vehicles - a 41 Ford 9N with the direct pushbotton switch design, a 1951 Ford 8N with the pushbuttton used to switch a starter relay/solenoid, and a 1962 Triumph TR4 with a starter relay/solenoid switched by the rotary key switch. These are all Bendix type starters.

A modern solenoid starter does not have a bendix drive. It uses a solenoid actuated plunger to mechanically extend the pinion gear into the ring gear. The solenoid mechanism also closes a set of contacts inside the case which switch motor current. They solenoid can be energuzed directly via the key switch or indirectly be a relay that is energized by the key switch. See the cutaway view I posted earlier.

Dan

 

[Vigo]

So electrical issues aside (jumping at the starter wont damage anything electrically) the damage you’ll cause comes from the arcing when forming that connection. Every time you do it you will leave small pockmarks on the parts. If for example you do this on a threaded stud a bunch of times, you may find the nut doesnt want to go over those damaged threads if you ever want to take it off.

But that’s about it. If making a high current connection (i wouldnt say this is high, just saying in general) on a part you dont want to physicaly damage with arcing, its best to connect jumper wires to the part first, and then connect the other end of the jumpers to each other. That way the arcing damage accumulates on your jumper wires instead of the part you’re jumping.

 

[GreensvilleJay]

You can minimize the damage of acing by adding the properly sized capacitor across the switch contacts.
Think old skool 'points' aka Kettering ignition system and the condensor inside the distributor cap.
A lot of mechanical relays I dealt with in the steel mill I added a 'snubber' made from a resistor in series with a capacitor. Installing them ELIMINATED the annoying 2AM service calls......

 

[TheOldHokie]

So electrical issues aside (jumping at the starter wont damage anything electrically) the damage you’ll cause comes from the arcing when forming that connection. Every time you do it you will leave small pockmarks on the parts. If for example you do this on a threaded stud a bunch of times, you may find the nut doesnt want to go over those damaged threads if you ever want to take it off. 9th

But that’s about it. If making a high current connection (i wouldnt say this is high, just saying in general) on a part you dont want to physicaly damage with arcing, its best to connect jumper wires to the part first, and then connect the other end of the jumpers to each other. That way the arcing damage accumulates on your jumper wires instead of the part you’re jumping.

Or better yet install a switch

Dan

 

[Sparty047]

Just EXACTLY what are you trying to do?

Now I am confused.... your tractor has a "starter relay" ????

Most engines which use a bendix type of starter has a relay built into the starter.
Does your starter have ONE BIG WIRE... or also have a small 'signal' wire to initiate starting?

Explain again why you do not simply FIX the problem instead of rewiring the starting system?

{The starter circuit has a starter relay switch (Kubota term in their shop manual).....not to be confused with the relay on the starter itself. For more detail please refer to the thread on the electrical issue with my starter system. I am NOT jump starting the starter motor itself.....I am "bridging" the red and black leads coming into the starter rely harness which holds the starter relay....(located behind the cowling above the instrument cluster) because the black lead is NOT delivering battery voltage due to some very high impedence within the circuit leading to it. Because of this low voltage this starter relay is NOT activated and does not send a signal to the engines starter motor (which contains its own starter relay)}

Using VOLTAGE DROP TESTING should take no more than 10 minutes to isolate the problem. At that point, your only issue would be to decide HOW to fix it.

You and others keep referring to the voltage drop test which I understand is done between the battery and the terminals on the starter motor itself (AND I"VE DONE THAT!). NO ONE has EXPLAINED if/how voltage drop testing can be used to isolate where the voltage drop originates within the starting circuit that lies behind the cowling. If it can be used to discover why the BL w WH stripe wire in the starter relay harness of the starting system is only rreceiving 10.5 V when the main switch is turned to "on" please feel free to be the first! Thanks.