ZD28 Mower with New Battery = New Problems

[black_cloud]

Hello, all
After overwintering with the battery disconnected, first attempt at restarting this spring was unsuccessful. Glow plug lamp was faint and fuel pump sounded as if it was struggling. After multiple attempts, I tried to jump the starter, but it didn't even engage. Given the battery was over 5 years old, it became the main suspect.

Replaced battery and new problems arose. Current status is the following:
o With Key in the ON position:
--- Fuel gauge and temperature gauge don't appear to be working. Fuel gauge needle is pegged to bottom as if it's reading negative.
--- No sound from fuel pump
--- Battery and oil pressure lamps are ON.
o With Key in Preheat position:
--- Glow pump lamp doesn't illuminate
--- Still no sound from fuel pump

Diagnostics completed:
- Battery terminal connections OK (across positive post and from negative post to engine block)
- All fuses in fuse bank OK
- 40 A slow blow fuse OK
- Main ignition switch was removed and continuity (not resistance) was checked across various terminals for different key positions. All OK. Continuity from switch terminals to wire connector also checked OK.

Right or wrong, I have not checked any of the safety switches as I struggle to see how they could be affecting the fuel/temperature gauge issues.

Per above, I didn't check resistance when checking the ignition switch. Perhaps this was a mistake?

Would greatly appreciate any suggestions. Any chance I could be dealing with a problem in the controller "combination box"?
Thanks in advance for your time.

 

[whitetiger]

What is the voltage of the new battery?
Double-check that it is not connected backwards.

 

[black_cloud]

Thanks for the question.
+12.5V across the terminals from positive to negative.
Given the weird fuel gauge behavior, I had wondered about the polarity as well, but couldn't see how it could somehow become reversed.

 

[whitetiger]

The combination box has nothing to do with the fuel pump and gauges.
Here is the wiring schematic.

 

[Mark_BX25D]

Diagnostics completed:
- Battery terminal connections OK (across positive post and from negative post to engine block)
- All fuses in fuse bank OK
- 40 A slow blow fuse OK
- Main ignition switch was removed and continuity (not resistance) was checked across various terminals for different key positions. All OK. Continuity from switch terminals to wire connector also checked OK.

HOW did you check the various connections? With a meter? Or a test light? Did you apply any load?

Meters can lie. If there is corrosion in a circuit, it will act as a high resistance. When there is no load on the circuit, the meter will show the correct voltage, but once you apply the load, the voltage can drop to near zero.

You must apply a load to be sure you have a good connection. A static test with a meter is not going to tell the whole story.

More explanation here.

 

[black_cloud]

The combination box has nothing to do with the fuel pump and gauges.
Here is the wiring schematic.

Thank you for the schematics, WhiteTiger.
Please forgive my ignorance, but what are these circled items representing?

 

[black_cloud]

HOW did you check the various connections? With a meter? Or a test light? Did you apply any load?

Meters can lie. If there is corrosion in a circuit, it will act as a high resistance. When there is no load on the circuit, the meter will show the correct voltage, but once you apply the load, the voltage can drop to near zero.

You must apply a load to be sure you have a good connection. A static test with a meter is not going to tell the whole story.

More explanation here.

Sure appreciate your helpful comments on high loaded resistance, Mark.
I did everything with a voltmeter under no load, so I could be misguided.
Given that this is a new battery, I imagine the primary candidate for excessive load resistance would be at the battery cable connections. Would you agree or should I be looking elsewhere?

 

[GreensvilleJay]

Meter pegging negative could say you hooked up the battery wrong.
What battery is it ? Common to have a 51R in small equipment these days.

 

[black_cloud]

Meter pegging negative could say you hooked up the battery wrong.
What battery is it ? Common to have a 51R in small equipment these days.

Thanks, GreenvilleJay.
It's a DieHard 51-2. 51R-2 didn't have the posts on the correct side.
I was worried about polarity as well, but definitely have +12.5V at positive terminal.

 

[Russell King]

Not to belabor the battery installation and correct voltage but your statement does not seem to prove the battery is connected to the tractor properly. As I understand your statement you are saying that from the battery positive post to some point gives you a positive 12.5 volts. I think that would be true EVEN if the battery was wired backwards to the tractor.

Please confirm that the battery is installed correctly by visually looking at the cable connected directly to the starter and follow it to the battery positive post or verify the negative battery terminal is connected to the frame (or something connected to the frame).

I don’t trust that a red cable is the positive cable or that a black cable is the negative cable. I have seen where both cables are black on the same vehicle or that a red cable was installed as the ground wire.

If you are 100% sure they are connected correctly you can just ignore this, I am just stating that your testing may be flawed from the statements you have made.

 

[GreensvilleJay]

Have to go back to gauge pegging negative. If it's still doing it, you've a) go the wrong battery( 51R when it should be a 51) or B) installed the cables wrong.
Wiring.PDF shows what looks like 'old skool' gages , so reversing the battery polarity WILL move the needle 'backwards'. It'll also probably destroy the rect/regulator as well ,that can 'disable' other 'stuff'.

Easy test. Connect -ve of meter to chassis frame, connect +ve lead to battery +ve. what do you get ?

 

[black_cloud]

So, just call me Black Cloud, the Idiot!
Wrong battery combined with deceptive wiring are the culprits.
After everyone's good suggestions, I dived into the wiring arrangement and found what I thought was the positive cable wired up to a star ground and what I thought was the negative going to the starter.

What threw me off down the wrong path was the protective boot (shown below), which in all my years, has always been on the positive cable. For some unknown reason, this is actually the negative cable going to the star ground.

I confirmed by reversing the wiring and now, with key ON, gauges work and fuel pump comes on.

Now, I've just got to get another battery with the posts swapped. Hopefully, that'll be the end of it.
Thanks to Mark, Jay, WhiteTiger and Russell for your help!!

 

[whitetiger]

Thank you for the schematics, WhiteTiger.
Please forgive my ignorance, but what are these circled items representing?


The items you have circled are the harness connectors; one harness plugs into the other.



View attachment 173185

 

[black_cloud]

Thanks for the clarification, WhiteTiger.

 

[GreensvilleJay]

I'm glad you FOUND the problem ! wonder if someone swapped the 'booted' cable when they swapped their battery ?

Yes, Positive posts are 'booted' to try to prevent sparks flying when you drop wrenches on batteries.....

 

[TheOldHokie]

So, just call me Black Cloud, the Idiot!
Wrong battery combined with deceptive wiring are the culprits.
After everyone's good suggestions, I dived into the wiring arrangement and found what I thought was the positive cable wired up to a star ground and what I thought was the negative going to the starter.

What threw me off down the wrong path was the protective boot (shown below), which in all my years, has always been on the positive cable. For some unknown reason, this is actually the negative cable going to the star ground.

I confirmed by reversing the wiring and now, with key ON, gauges work and fuel pump comes on.

Now, I've just got to get another battery with the posts swapped. Hopefully, that'll be the end of it.
Thanks to Mark, Jay, WhiteTiger and Russell for your help!!

View attachment 173206

Over the years I have seen plenty of ground cables with boots. I have never seen a black boot on a positive cable.

Dan

 

[Mark_BX25D]

Sure appreciate your helpful comments on high loaded resistance, Mark.
I did everything with a voltmeter under no load, so I could be misguided.

Yep. It can bite you! I learned this one the hard way as a radio technician working for a small business radio shop. I brought a "bad" radio into the shop 3 times before it dawned on the boss what I was missing when this radio would not power up. Turns out the truck's battery was out-gassing a lot and had corroded the connection I had made to the battery cable when I installed it. There was not a thing wrong with the radio, but my meter measured a solid 13.8v at the connection inside the cab, so obviously it was the radio, right?

Nope.

Given that this is a new battery, I imagine the primary candidate for excessive load resistance would be at the battery cable connections. Would you agree or should I be looking elsewhere?

Agree! That's the first place to check. And remember that cables can be corroded on the inside, and look okay on the outside. Flex them to see if they crackle.