Lazer Z only starts with assist of battery charger

[bertsmobile1]

No the problem can not be the voltage regulator.
The fuel pump should have a black & a purple wire attached to it ( if I have the correct diagram )
The black wire goes to the PTO Clutch then to it's own ground
So working on the bad ground theory check for ground on the black wire at the pump.

The purple wire goes into the engine so will be on a switch of some sort, most likely a pressure switch on the fuel line or a control relay.
To take that any further I will need the full engine number to see If we can't find the Kohler engine wiring circuit.
You could remove the engine cover to see where the purple wire goes, but I fear it will be into an ECU which will be a replace only item.

 

[GrassBarber]

Thanks, GrassBarber. Can you give me any more to go on? Is this something that's you've experienced? Is there a way to test the starter without replacing it first?

The reason that I ask is because the engine turns over and over with no problem with the key in the start position. It's just that it will only "fire" when the battery charger is hooked up, and only on the 55A setting. If I have it on the 10A setting for example, the mower cranks and cranks but still won't "fire". Here is what I've found in the Kohler Service manual which I found online:

When key switch is turned ON and all safety switch
requirements are met, ECU activates fuel pump module
for about six seconds, which pressurizes system for
start-up. If key switch is not promptly turned to start
position, engine fails to start, or engine is stopped with
key switch ON (as in case of an accident), ECU switches
off pump preventing continued delivery of fuel. In this
situation, MIL will go on, but it will go back off after 4
cranking revolutions if system function is OK. Once
engine is running, fuel pump remains on.

I'm not getting the six second buzz for the fuel pump module when I turn the key to the "on" position UNLESS the charger is connected, and on the 55A setting.

Thanks!

Don’t replace the starter, I’m having reading comprehension issues. Miss the “engine turns over”

My apologies

 

[mowerman556]

No the problem can not be the voltage regulator.
The fuel pump should have a black & a purple wire attached to it ( if I have the correct diagram )
The black wire goes to the PTO Clutch then to it's own ground
So working on the bad ground theory check for ground on the black wire at the pump.

The purple wire goes into the engine so will be on a switch of some sort, most likely a pressure switch on the fuel line or a control relay.
To take that any further I will need the full engine number to see If we can't find the Kohler engine wiring circuit.
You could remove the engine cover to see where the purple wire goes, but I fear it will be into an ECU which will be a replace only item.

Thanks for the info. I'm out of pocket for a few days with elder care issues. I will get back into this early next week (June 25-26), and let you know what I find. The engine is a CH745. The serial number is rubbed off from the rubber cover that hides the engine shaft vibrating against it over the past 14 years (remember this mower is in a residential setting, and I use it once a week in summer, twice a week in wet weather. FWIW, it is always stored indoors, and kept under mild heat (40 degrees-ish) when the temps dip below 10F or so.) Is the serial number located anywhere else?

More next week,

mowerman556

 

[mowerman556]

No problem, GrassBarber. Done it on more than one occasion myself. have a good weekend!

 

[mowerman556]

No the problem can not be the voltage regulator.
The fuel pump should have a black & a purple wire attached to it ( if I have the correct diagram )
The black wire goes to the PTO Clutch then to it's own ground
So working on the bad ground theory check for ground on the black wire at the pump.

The purple wire goes into the engine so will be on a switch of some sort, most likely a pressure switch on the fuel line or a control relay.
To take that any further I will need the full engine number to see If we can't find the Kohler engine wiring circuit.
You could remove the engine cover to see where the purple wire goes, but I fear it will be into an ECU which will be a replace only item.

With apologies for the delay, I got back into the mower this morning. Connections all checked out okay. On finding the fuel pump, it does have a black and a purple wire on the terminals. I placed a DC volt meter on the purple lead and ground (chassis) with the key in the on position. I did not get the 6 second fuel pump buzz, which has been the problem all along. The volt meter read zero volts. I then put the battery charger across the battery terminals on the 55A setting. When I turned the key, the fuel pump buzzed as it should. Taking the same DC voltage reading between fuel pump purple wire at the terminal and chassis ground, I had a good 12 vdc reading. Hope this helps narrow things down?

The engine serial number is 3303900991. That's on the triangular cover plate on the front of the motor, close to the intake manifold. Engine model is PS-CH745-0003 Note there is the gray "box" secured to the left inner side of the frame. That has a different engine serial number on it? that one says 3409613431.

Any further thoughts would be appreciated, and again, TIA!

 

[Boit4852]

Personally, I have found that the electrical systems on mowers, cars, trucks, etc. will benefit from adding hyper grounds. These are added ground wires from the battery negative anode(connection) to the chassis and engine. Cleaning the connections points well and then adding a generous dab of di-electric grease after the connection is made will add reliability. This reduces corrosion. No matter what, electrical issues on our machines can typically be traced to a corroded connection, whether ground or hot. As an example, my 2006 Japanese made motorcycle began experiencing an electrical issue that was driving me mad. Symptom began when activating the turn signal which would cause the engine to surge and feel as though it was misfiring, then it escalated to stalling when I applied the brakes. What the heck? Long story short, the culprit was a badly corroded ground connector about 8" from the negative battery anode. It was so corroded that once I forced the connector apart, it disintegrated in my hand. I had to cut the connector out and use a WAGO connector in its place. I also used a heavier gauge marine gauge wire to reestablish this important ground. Not only was the problem solved, but I notice that the engine starter spins the engine quicker and the engine starts immediately vs a few seconds before. Lesson is that a good strong ground is super important.

 

[bertsmobile1]

Personally, I have found that the electrical systems on mowers, cars, trucks, etc. will benefit from adding hyper grounds. These are added ground wires from the battery negative anode(connection) to the chassis and engine. Cleaning the connections points well and then adding a generous dab of di-electric grease after the connection is made will add reliability. This reduces corrosion. No matter what, electrical issues on our machines can typically be traced to a corroded connection, whether ground or hot. As an example, my 2006 Japanese made motorcycle began experiencing an electrical issue that was driving me mad. Symptom began when activating the turn signal which would cause the engine to surge and feel as though it was misfiring, then it escalated to stalling when I applied the brakes. What the heck? Long story short, the culprit was a badly corroded ground connector about 8" from the negative battery anode. It was so corroded that once I forced the connector apart, it disintegrated in my hand. I had to cut the connector out and use a WAGO connector in its place. I also used a heavier gauge marine gauge wire to reestablish this important ground. Not only was the problem solved, but I notice that the engine starter spins the engine quicker and the engine starts immediately vs a few seconds before. Lesson is that a good strong ground is super important.

Bolt might have it.
On more than one occasion I heave needed to run an extra ground to the engine to get a mower to behave.

 

[mowerman556]

Personally, I have found that the electrical systems on mowers, cars, trucks, etc. will benefit from adding hyper grounds. These are added ground wires from the battery negative anode(connection) to the chassis and engine. Cleaning the connections points well and then adding a generous dab of di-electric grease after the connection is made will add reliability. This reduces corrosion. No matter what, electrical issues on our machines can typically be traced to a corroded connection, whether ground or hot. As an example, my 2006 Japanese made motorcycle began experiencing an electrical issue that was driving me mad. Symptom began when activating the turn signal which would cause the engine to surge and feel as though it was misfiring, then it escalated to stalling when I applied the brakes. What the heck? Long story short, the culprit was a badly corroded ground connector about 8" from the negative battery anode. It was so corroded that once I forced the connector apart, it disintegrated in my hand. I had to cut the connector out and use a WAGO connector in its place. I also used a heavier gauge marine gauge wire to reestablish this important ground. Not only was the problem solved, but I notice that the engine starter spins the engine quicker and the engine starts immediately vs a few seconds before. Lesson is that a good strong ground is super important.

Thanks Boit4852. Already added the extra ground, and no change in the symptom. Again, under normal operation when the key is turned to "on" position the fuel pump should run for six seconds, then stop, after which the key can be turned to the start position to start the engine. In my case, the fuel pump does not cycle for those six seconds. Nothing happens. Obviously, without that "prime", if I turn the key to "start" position the engine cranks and cranks, but will not fire.

From Bertsmobile1's earlier comments I did add a secondary ground wire see pic), of the same or similar gauge as the factory wire. I attached this to the same lug on the engine that the battery negative is connected to. I also then connected the other end (under existing nut or bolt) to various parts of the engine, including the lifting hook, and to various parts of the frame. In ALL cases, when I turn the key to "on", the fuel pump still did not cycle for six seconds as it should. I also left the key in the "on" position, and with the other end of auxiliary ground wire loose in my hand, I did a "touch test" to various parts of the engine and the frame. Same situation, fuel pump does not cycle.

Further troubleshooting, I found that when I turn the key to the "on" position, the terminal with the purple wire on the fuel pump reads 0 volts DC.

The only way the engine will start is when I put a battery charger across the battery, on the 55A setting. When I do that and turn the key to the "on" position the fuel pump cycles, and the engine starts. In that situation, the purple wire on the fuel pump also has 12 VDC on it.

I thought about relays, but that doesn't make sense for why the battery charger starts the mower. Once the engine starts, I can mow for 2-3 hours with absolutely no issues whatsoever. Soon as I turn it off, however, it will not start again without the battery charger on it. (I had replaced the battery already, if you hadn't read back.)

I'm starting to think ECU.... thoughts?

Thanks,

mowerman556

 

[bertsmobile1]

Well it does sound like the ECU is on the way out.
OTOH it is an expensive piece of kit to replace if there is nothing wrong with it.
On the nigh charge setting the output voltage on your charger is going to be around 14V if not more untill a heavy load is put on it.
This tends to favour a voltage drop somewhere between the battery and the ECU but we are running out of options.
You may have a wire broken at a terminal but we are getting into the drowning man clutching at straws territory now.

 

[Boit4852]

View attachment 39203

Thanks Boit4852. Already added the extra ground, and no change in the symptom. Again, under normal operation when the key is turned to "on" position the fuel pump should run for six seconds, then stop, after which the key can be turned to the start position to start the engine. In my case, the fuel pump does not cycle for those six seconds. Nothing happens. Obviously, without that "prime", if I turn the key to "start" position the engine cranks and cranks, but will not fire.

From Bertsmobile1's earlier comments I did add a secondary ground wire see pic), of the same or similar gauge as the factory wire. I attached this to the same lug on the engine that the battery negative is connected to. I also then connected the other end (under existing nut or bolt) to various parts of the engine, including the lifting hook, and to various parts of the frame. In ALL cases, when I turn the key to "on", the fuel pump still did not cycle for six seconds as it should. I also left the key in the "on" position, and with the other end of auxiliary ground wire loose in my hand, I did a "touch test" to various parts of the engine and the frame. Same situation, fuel pump does not cycle.

Further troubleshooting, I found that when I turn the key to the "on" position, the terminal with the purple wire on the fuel pump reads 0 volts DC.

The only way the engine will start is when I put a battery charger across the battery, on the 55A setting. When I do that and turn the key to the "on" position the fuel pump cycles, and the engine starts. In that situation, the purple wire on the fuel pump also has 12 VDC on it.

I thought about relays, but that doesn't make sense for why the battery charger starts the mower. Once the engine starts, I can mow for 2-3 hours with absolutely no issues whatsoever. Soon as I turn it off, however, it will not start again without the battery charger on it. (I had replaced the battery already, if you hadn't read back.)

I'm starting to think ECU.... thoughts?

Thanks,

mowerman556

You've taken a good first step to solve this issue. To respond to your comment about the relay, let me add info about my recent experience with the starter relay on the motorcycle I mentioned in my other post. Starter relays is nothing more than a switch that 'relays' high current to the starter motor. Sounds to that the high current contacts inside the relay have finally either corroded or have worn out to the point that the relay won't send enough current to spin the starter motor to start the engine. My motorcycle is a '06 Suzuki that due to age, is beginning to have issues. Along with making my own grounds, I also changed the starter relay. It was the original relay. The high current contacts DO corrode and wear out. By you using the high amp charger, that forces high current across those contacts that you are not getting form the battery and you can start the engine. Once it is running and you release the ignition key, the starter relay breaks current across the contacts to the starter motor and has zero effect on whether the engine runs or not. My recommendation is to test the starter relay or just replace it. These relays are more expensive than a run of the mill relay. These are specialized. The starter relay for my Suzuki was nearly $80. I changed the relay on my Exmark last year and if my memory is correct, it was under $40.