Starter runs as soon as battery connected.

[J.O.A.T-M.O.N]

I've finally got the motor in and am ready to apply power. With the starter switch off (and through process of elimination disconnected) as soon as I connect the negative wire to the battery the starter kicks in and cranks the motor. I'm suspecting a bad smart start box but would like to dig in further before spending the money on a hunch. It's a 6.5L non turbo th400 m1097a1. The box is a KDS CR-2700. I have never had this truck running as of yet. As I am trouble shooting I have disconnected the trigger wire to the starter (74A) and hooked up a test light so I'm not arching the battery terminal. I've gone as far as disconnecting the interior cannon plug from the start box and when I connect the battery I still get power to wire 74a. If I had board level schematics I could go further into testing the system but without those its just a magic box. What else could trigger it to power the starter? What other info would help in figuring this out? Thanks!

 

[MarkM]

Do you have a key switch? They tend to have issues.

Mark

 

[J.O.A.T-M.O.N]

Do you have a key switch? They tend to have issues.

Mark

No. Running the original switch.

 

[Mogman]

Not likely the EESS, the start circuit just passes through the box, You can disconnect both connectors and try.
You can also slide under it and disconnect the start lead from the starter.
BE VERY CAREFUL!! that arc at the battery can cause a battery explosion, wear safety gear when messing with it until you get that figured out.
Sorry, miss read so you already disconnected the start wire, Disconnect the batteries and pull the inside plug off of the EESS, connect batteries and try again, still hot to the start wire disconnect the batteries and then remove the engine side plug from the EESS and try again.

 

[MarkM]

If the starter is not shimmed properly the bendix gear could get jammed on the flywheel teeth and that could cause the issue. Was it trying to engage when you first hooked up the batteries or the first time you turned the lever to start?

Mark

 

[J.O.A.T-M.O.N]

Not likely the EESS, the start circuit just passes through the box, You can disconnect both connectors and try.
You can also slide under it and disconnect the start lead from the starter.
BE VERY CAREFUL!! that arc at the battery can cause a battery explosion, wear safety gear when messing with it until you get that figured out.

It must do more than just pass through it. With the start switch totally disconnected it still sends voltage to wire 74a to the starter. If I disconnect the cannon plug from the engine side of the EESS, There is no power going anywhere as it's supplied on pin e wire 81a. Also on that same plug on pin I is wire 74a that goes to the trigger wire. I've alleviated the arch by disconnecting the wire at the starter and putting a 24v test light in series to ground so all it does now it light the light so I can see there is power, not crank the motor. Drawing less amps so no arching. Thanks for the input though.

 

[Mogman]

If the starter is not shimmed properly the bendix gear could get jammed on the flywheel teeth and that could cause the issue. Was it trying to engage when you first hooked up the batteries or the first time you turned the lever to start?

Mark

Good question!!

 

[J.O.A.T-M.O.N]

If the starter is not shimmed properly the bendix gear could get jammed on the flywheel teeth and that could cause the issue. Was it trying to engage when you first hooked up the batteries or the first time you turned the lever to start?

Mark

The first time I hooked it up. I've never gotten to turn the lever to start it. I've been under and can visually see the bendix gear is pulled away from the flex plate.

 

[Mogman]

It must do more than just pass through it. With the start switch totally disconnected it still sends voltage to wire 74a to the starter. If I disconnect the cannon plug from the engine side of the EESS, There is no power going anywhere as it's supplied on pin e wire 81a. Also on that same plug on pin I is wire 74a that goes to the trigger wire. I've alleviated the arch by disconnecting the wire at the starter and putting a 24v test light in series to ground so all it does now it light the light so I can see there is power, not crank the motor. Drawing less amps so no arching. Thanks for the input though.

Have you tried it with the inside plug pulled off of the EESS and the outside plug connected?
If so then it must be in the box, could be full of water among other things.

If you only have the inside plug removed and there is no start signal then it is in the dash wiring.

 

[TOBASH]

Start goes through pin B dashboard 8 pin side (EDIT - correction… A pin) and pin I under hood nine pin side. I would think a short in the PCB EESS could do this, although a bad ignition switch or stuck solenoid is more likely.

Lightly strike the solenoid and starter with a hammer and see if the problem resolves. If so, it is the starter.

 

[J.O.A.T-M.O.N]

Have you tried it with the inside plug pulled off of the EESS and the outside plug connected?
If so then it must be in the box, could be full of water among other things.

If you only have the inside plug removed and there is no start signal then it is in the dash wiring.

I have tried it with the inside plug off and the outside plug connected and it still does it. I've got the box open right now in front of me trying to ohm it out. No water or viable signs of anything. Looks brand new inside.

 

[J.O.A.T-M.O.N]

Start goes through pin B dashboard 8 pin side and pin I under hood nine pin side. I would think a short in the PCB EESS could do this, although a bad ignition switch or stuck solenoid is more likely.

Lightly strike the solenoid and starter with a hammer and see if the problem resolves. If so, it is the starter.

The print I have shows pin B is the run side of the switch. Pin A is the start. Maybe I have the wrong print? Pin I is the trigger wire going to the starter. That's the one getting voltage and engaging the starter that part of my print must be correct.
If it were a stuck solenoid it would engage even with the 74a wire (pin I) disconnected and it doesn't. The key switch and in fact all of the wires inside have been disconnected and I am still getting power to the 74a wire as soon as I connect the battery. These are all great thoughts, but it's got to be something else.

 

[J.O.A.T-M.O.N]

Update - I can measure 0 ohms from pin E (would be wire 81a) to pin I (would be wire 74a) on the engine side of the EESS box. That would supply incoming battery voltage directly to the starter. A direct short. Now to see if I can find the short inside the box. If anyone has any experience working on the printed circuit board or has board level schematics I could use those. Thanks for all the suggestions!

 

[TOBASH]

Pins as I have identified.

 

[TOBASH]

The print I have shows pin B is the run side of the switch. Pin A is the start. Maybe I have the wrong print? Pin I is the trigger wire going to the starter. That's the one getting voltage and engaging the starter that part of my print must be correct.
If it were a stuck solenoid it would engage even with the 74a wire (pin I) disconnected and it doesn't. The key switch and in fact all of the wires inside have been disconnected and I am still getting power to the 74a wire as soon as I connect the battery. These are all great thoughts, but it's got to be something else.

Correct. A pin.

Perhaps I need a new prescription?

 

[Mogman]

Maybe the "smart start" boxes have a relay or FET switch controlling the starter.
Unfortunately I have not found any board level documentation, there are allot of different boxes.
This does not mean they are not out there!!
I generally just go in and trace the circuit I am having issues with.

 

[TOBASH]

Maybe the "smart start" boxes have a relay or FET switch controlling the starter.
Unfortunately I have not found any board level documentation, there are allot of different boxes.
This does not mean they are not out there!!
I generally just go in and trace the circuit I am having issues with.

I was thinking the same thing. KDS EESS especially is all solid state. SSI boxes are also all solid states. All the boxes aside from maybe the Amtek/Prestolites have breadboards with IC’s. Easy for units like that to blow an IC or part of the breadboard and have weird issues.

What EESS PCB do you have?

 

[J.O.A.T-M.O.N]

I was thinking the same thing. KDS EESS especially is all solid state. SSI boxes are also all solid states. All the boxes aside from maybe the Amtek/Prestolites have breadboards with IC’s. Easy for units like that to blow an IC or part of the breadboard and have weird issues.

What EESS PCB do you have?

 

[TOBASH]

That is a KDS smartbox.

 

[Mogman]

I would poke around what looks like a lone relay, IIRC the 4 together is the run relay(S) used to be one big one, the FETs are for the per-heat