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Raymcgill

New 728

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Raymcgill

Well, I just bought my first tractor!

It doesn't get any power to the Starter, and I found the shifter interlock spliced together. I a getting weird readings, and am considering just taking everything apart and cleaning it first.

I looked for a Starter Troubleshooting guide, but didn't see one. I would be glad to document one if needed. Am I on the right track?

1. Check battery (I did, ended up with new one)

2. Check shifter interlock fittings attached (mine was removed and spliced together)

3. Check front PTO interlock fittings attached

4. Check continuity with battery removed.

4.1 Check shifter and PTO interlocks. Measure resistance between top left (blue) wire of ignition switch and Bottom wire of ignition switch [?? not sure]. Should be zero because interlocks are met.

4.2 Check continuity between x/y [?? not sure. What is best points to check between battery, solenoid, starter, etc?]

4.3 Check continuity between x/y [?? not sure]

5. Replace Battery. Check power to starter

5.1 Battery > 12.5v

5.2 Setup voltmeter between gnd and big starter wire. Key to start. Should see battery Voltage??

Thanks in Advance,

Raymond

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mbinwi

Hi Ray, welcome to the group. I'm a recent member myself. I do have a little time under my belt, refurbishing a 700 last summer. I have 2 recently acquired 738's and I'm going through the same ignition thing as you are, with one of them. Since I have one that starts and runs, I noticed on the ignition switch, there are 4 poles, 3 parallel with each other, 2 on the top and 1 on the bottom, and one pole perpendicular to the other three. On the working switch, with a tester, and the key all the way over to engage the starter, the top pole lights up, sending power to the solenoid, and then to the starter. On the non-working switch, with the key engaged, the top pole does not light up, so no power goes to the solenoid or starter. So, my next step will be to replace the switch. The 2 safety lock-out switches on mine were jumped, by the previous owner. Just thought I'd pass all this along to you.

Good luck !

Mike.

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Ronald Hribar

BEWARE

There are different ignition switches depending on what kind of ignition system you have on tractor

Wrong one will burn up the ignition system

On the safety circuit. You mentioned interlock module

Some of them interrupt the ground

So you will get strange readings

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Raymcgill

Thanks, Mike.

I found a Repair Manual online which has more information.

ignition has four poles, one of which (L) is used for an Hour Meter. That leaves three labeled B M S. B goes to battery (indirectly), M goes to Magneto, and S goes through the two safety switches to the Solenoid middle connector labelled C. (Solenoid B goes to Battery, Solenoid A goes to Starter Motor.)

So. I would guess ignition switch S should only be energized when in the start key position so that we connect the battery to the starter. Otherwise the Starter Motor acts like a generator and goes to the voltage regulator? (This part is fuzzy)

I am going to take it apart tonight and try to clean all the terminals.

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BLT
quote:Originally posted by Raymcgill

So. I would guess ignition switch S should only be energized when in the start key position so that we connect the battery to the starter. Otherwise the Starter Motor acts like a generator and goes to the voltage regulator? (This part is fuzzy)I am going to take it apart tonight and try to clean all the terminals.


id="quote">
id="quote">That is correct, you have a starter generator(S-G). On the "A" terminal of the S-G, you have a wire that goes to the voltage regulator (14ga) and also a 4 ga wire that runs to a 12V relay. When that relay is energized thru the key switch, the unit will motor to start the engine. This was quite common for garden tractors produced in the 60's and 70's.

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Raymcgill

So, Bob, to clarify troubleshooting:

I should get 12v to the battery side (B) of the relay (solenoid) always.

I should get 12v to the center © when the key is turned to Start.

I should get 12v at the starter side of the relay (A) and at the starter when the key is at Start.

Should I hear the solenoid go click?

Should I measure anything at the voltage regulator?

Thanks,

Raymond

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Raymcgill

I just found the procedures I was looking for. I misplaced the download link, but it is the Maintentance Guide for the 728 Broadmoor tractor series. It has the procedures on testing each component except the generator. I guess if I get voltage at the generator and it doesn't crank, it must be bad?

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BLT

There is also a 20 amp fuse in the system.

Providing everything is fine, you can use a jumper wire from the battery side of the relay and then touch smsll terminal of the relay to see if starter fuction. It also tells you relay is also OK.

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mbinwi

Not to butt in your reply to Ray's post, thanks for that info, Bob, I was going to try that on my tractor #2, that I have been posting about today, as I think the ignition switch is bad. No power from the switch to the relay.

Mike.

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Raymcgill

Well, I spent another hour and still scratching my head. I did the procedure for the solenoid/relay. With battery out, B-D, B-A, B-Ground should all be infinite. I didn't get that. I took out the solenoid. Clean the outside and the connections. I put it back. I turned the key and heard the clunk, clunk as I expected. Then no clunk when I went to measure. Multimeter (Sears Craftsman) sucks. Sometimes infinite, sometimes 80M. I have no idea still.

It would appear the solenoid is bad, but the starter still did nothing.

So, is there a site sponsor who sells parts that anyone would recommend? I would rather support the site than a generic Google result.

Should a jumper 12v directly to starter?

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BLT

You can go direct with battery. Disconnect 4 gauge wire from starter relay to SG. Battery ground to generator body and battery plus to 4 gauge wire. The reason you go to wire is so you don't damage terminal on SG.

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Raymcgill

What a strange ride this has been! I applied 12v to the Center © terminal of the solenoid and got a click today. I tried all key positions, and nothing. My troubleshooting showed that the keyswitch wasn't allowing the 12v to the solenoid. I then was measuring for voltages on the voltage regulator, when all of a sudden the engine and starter started spinning (I had removed gas tank and spark plug). Key was already OFF. I had to remove the battery cable to get it to stop.

So, when everything was said and done, key works, solenoid works, Starter works and it all works like it is supposed to. I have no idea why, but I cleaned everything and exercised everything. Maybe I exorcised everything?

BTW, the starter needs the Field lead energized to start, so putting 12v on big lead of starter is NOT a valid way to test.

Thanks to Mike, Ronald, and specially Bob Tiarks who gave assistance!

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mbinwi

Good deal Ray, glad everything is working. I got my electrical/starter problems figured out too. I needed an ignition switch, as the switch wasn't allowing the current to the relay/solenoid, like what you had. I did the "jumper" thing that Bob suggested, which made everything work, and led me to the switch.

I'm now working through tranny problems, with a lot of great help from members, just like last summer when I did the 700. I have pics in my profile. I love this forum!

Mike.

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powerking_one

Ray,

You stated "BTW, the starter needs the Field lead energized to start, so putting 12v on big lead of starter is NOT a valid way to test."

For a healthy/normal starter-generator, this is not true. What differentiates these from a std generator only is the design of the two field coils. The "A" (armature field coil) is a heavy gauge wound one in series with one of the commutator brushes; the other brush is grounded. Thus when +12V is applied to the "A" terminal, this field coil gets full starter current and provides a very strong magnetic field and the S/G becomes a very high torque DC motor. The "F" terminal can be open circuit for this test and does not come into play. The "F" (field coil) is wound with much thinner wire and is used for the generator mode of the unit. In your case, if the only way to get the S/G to spin is to externally apply +12V to the "F" along with the "A", that suggests the starter "A" field coil is defective (probably open).

Tom(PK)

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Raymcgill

Thanks, Tom (PK)!

Good description. I look forward to getting past the electrical stage and into the Engine stage. I think it will be OK because I have already tested for good spark. Then I have to figure out if I have belts and where they go. And how to hook up the mower. Whew! Lastly, I need to learn how to drive a tractor. I'm looking forward to that.

Here is what I think is true about the 728 Belts

Drive belt Length (inches) 85.3 Part# 165048

Rotary Mower, 36",belt Length 70.1 Part# 108505

The tiller and snowblower have belts wrapped with them, so I assume they fit. I was going to use them as examples of what shape/style to get for the drive and mower belts.

Any belts different than others? Any issues with getting a generic belt?

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powerking_one

This is a good quick field test of a stand alone S/G there Bob, but it also does not tell all about the overall health of the S/G. Case in point is there can be a commutator segement short/open or armature winding short/open and the unit will "appear" to be OK via this test. If one of the above conditions are true, with it on the engine, either the starter torque is weak and/or the generator is low on output. My 3314H had a blown out winding on the armature and it produced low starting torque along with the "GEN" light coming on near full throttle; found the piece of winding in case of the S/G.

Tom (PK)

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Raymcgill

The adventure continues. I checked compression... 25#, but my smart brother tells me since this motor has sat awhile, and the carb may have been open to redo the test.

1. squirt some oil down the carb to get fresh oil on the piston and rings.

2. Use ether/starting fluid to test carb and if engine will run

3. Retest compression with throttle shut.

sound good? If it fails I will take to mower mechanic to evaluate it and consider cost of engine swap. I am planning on mowing 2-3 acres of grass. Everyone I show the tractor to scoffs at 8HP, and says that their 18+ is barely good enough.

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powerking_one

Ray,

Have you actually tried to start the engine? Even if the S/G has a problem, there should be a rope start pulley on top of the flywheel pulley. Do you have good spark? If the compression is indeed that low in the 25 lb range, that's not enough for it to fire. L-head B&S engines typically should build to 75-100 lbs (done with the throttle wide open) after a few crank revolutions if healthy.

Tom (PK)

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Raymcgill

The starter, solenoid, and key switch now work with just a little cleaning of contacts and luck.

I put some gas in, and checked plug sparking, then tried to start. No bank at all. I will use ether tonight and some fresh gas and hope to get it running. (using process defined last note).

Then I need to get a belt for mower, figure out how it attaches.

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Raymcgill

Bob, I have that book. I don't see how to hook up the mower deck, specifically where the belts go. I am sure it might be obvious when I do it. Do you have any guides for mower/tiller/showblower?

I haven't found those anywhere.

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Raymcgill

Thanks, Bob. I appreciate the link. Exactly what I needed.

Also, I spent my lunch hour playing with the 728.

I put oil down the mouth of the carb air intake. Wow, a huge mess because 1. the screw mounts through the bottom the casing which means there's a hole straight down, and 2. There is some funky thing on the back that isn't quite connected. See picture (1)

I then used ether to try to start. Fired right up, with no hesitation. Unable to get carb to start, though.

https://lh6.googleusercontent.com/-bA0ehTREgvI/Uaj2G2XOuhI/AAAAAAAAEhg/0pnPJ7aF6Wc/w504-h383-no/TractorCarb.jpg

Checked Compression.... 75#!!!! Woohoo!

I think the next steps are to yank the carb and just clean it well, and restore to factory settings. Also need to fix choke cable which doesn't move correctly. (3) on image

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