Engine goes under load then snubs out

[Achto 26,500]

I had to write this up because I couldn't believe it my self.

 

I've been tinkering around with my new to me C-145 hydro. Nothing too intense, new ignition switch, starter solenoid, plug the DC wire back into the regulator, oil change, & new muffler.

 

Any way while driving it around the engine would go under a heavy load to the point of snubbing out. Stranger than that, turn the key & it would start right back up again. I could drive it a short ways & then the issue would repeat. If I ran at 1/2 throttle or less it would not happen. I assumed that I was having hydro problems. Then I was able to make the symptom repeat it's self with the drive belt disengaged. OK what could be left?!?! If a bearing in the engine was locking up, why would it start right back up again? While doing more investigating I noticed that it had stopped charging. Tested the stator & was getting 30vac at 3/4 throttle & above. OK the regulator took a dump no big deal, right? Plug the reg back in & go for another cruise. Symptom occurs again. Then it hit me, the only thing left that could possibly put load on the engine was the stator. I unplugged the regulator & took yet another cruise, this time how ever it ran flawlessly. I drove around for about 20min + with absolutely no issues.

 

I have never seen this before but apparently the voltage regulator / rectifier must be shorting out, connecting the two lines from the stator together creating enough load to snub the engine out. I would never had thought that the charging stator could have pulled enough KW to stop the engine. 

 

This was sooo odd that I wanted to share this info with people. Hopefully this is some thing you can add in with your trouble shooting skills.

Edited September 29, 2018 by Achto

[oldredrider 2,547]

Definitely a rare occurance. It might be interesting to repeat the situation on a bench. Next time I have one up there, I'll try shorting the stator and see what happens... Of course it'll be someone else's motor! Just kidding.

Thanks for the heads up.

[953 nut 51,487]

Never would have thought that a 36 volt 15 amp (540 Watt maximum) load would kill a 14 HP engine. Interesting!

[Achto 26,500]

8 hours ago, 953 nut said:

Never would have thought that a 36 volt 15 amp (540 Watt maximum) load would kill a 14 HP engine. Interesting!

 

I agree it should take 9000w + to stop a 14hp engine.

Edited September 29, 2018 by Achto

[squonk 38,844]

I'm thinking the electrical snafu is sucking enough current to drop the system voltage to the point the ignition system is compromised causing the engine to bog down.

 

I had an old Chevy that developed a short in the tiny tiny brake  light switch. This happened at night. I'm driving along and hit the brakes. Not only did my headlights go out, but the entire electrical system shut down. Engine shut off -everything. As soon as I let off the brake everything came back on  and I was able to restart the engine. 

[JimmyJam 516]

Interesting!    

[Achto 26,500]

1 hour ago, squonk said:

I'm thinking the electrical snafu is sucking enough current to drop the system voltage to the point the ignition system is compromised causing the engine to bog down

 

I agree, this may have been a contributor. It was just odd how much load that it actually put on the engine. It would not stop with out a struggle, if fact it tried so hard to pull the load that it burnt most of the paint off of my new muffler. It acted more like you were trying to pull 20hp out of a 14hp engine. The first time that it happened I fully expected to find a smoking belt & a locked up pulley.

Edited September 29, 2018 by Achto

[WHX?? 46,681]

It is bizarre, I would have thought some smoke would have been let out of the reg, stator or any wiring in between. Had to be a rather large current path somwhere??? Keep us posted when you replace the reg.

[953 nut 51,487]

My guess would be the "B+" terminal on the regulator is shorted to ground and when you connect the wiring harness to it the voltage is being drawn down like Mike @squonk described. I think the wire (orange I believe) is a 12 gauge and can carry a fair amount of current (40 amps or more) before it will smoke.

[ebinmaine 62,949]

On 9/29/2018 at 9:00 AM, WHX21 said:

Keep us posted when you replace the reg.

[Achto 26,500]

An up date on this issue - I replaced the regulator this week & threw a meter on it. Every thing checked out as it should, no continuity to ground on the stator, 40VAC at 3600RPMs from the stator, 14.2VDC from the regulator. . Took it for a short ride & life seemed good again. Later on that day I took it for a longer ride & surprise! the problem returned . I unplugged the regulator & the tractor ran with absolutely no issues (other than not charging ). I guess the next step will be to pull the fly wheel & inspect the magnets. If the magnets look good then I'll try replacing the stator. Might take me a bit to get to that, but I'll keep you posted on my findings.

[WHX?? 46,681]

This is a real stumper. I was ready to blame it on a gas feed problem or other issue but why does it go away with the reg unplugged? That and the fact it starts right back up.  There isn't much for wiring on this tractor and was all checked twice by different sets of eyeballs. Keep in mind this is a battery powered ignition/points motor.

 

The other strange thing I thought as there was zero resistance through the stator. One would think all coils of wire would have a couple of ohms resistance?

 

Maybe a guy should temporary  the other old non-workin reg on for troubleshooting so as not to worry about letting the smoke out of a brand new working one?

4 hours ago, Achto said:

be to pull the fly wheel 

Should maybe do that anyway to check for mice and dirty fins.

[pfrederi 17,120]

On my older units with a Starter/Generator you can ground the field coil to force the generator to maximum output.  It does make a difference in the engine speed but it is slight nowhere near stalling out.  To nearly stall out you would have to be drawing a huge amount of current... you would think something would start burning or melt.

[WHX?? 46,681]

1 minute ago, pfrederi said:

something would start burning or melt.

One would think so that's why I'm not ruling out some other ignition problem. Any chance the coke is flopping closed and snubbing her out? Doesn't explain the unplugged thing but trying to look at things from all angles.

[953 nut 51,487]

On 9/29/2018 at 2:17 PM, 953 nut said:

My guess would be the "B+" terminal on the regulator is shorted to ground and when you connect the wiring harness to it the voltage is being drawn down like Mike @squonk described. I think the wire (orange I believe) is a 12 gauge and can carry a fair amount of current (40 amps or more) before it will smoke.

Have you substituted a new wire fir the old one going to the regulator "B+"? I think the wire travels behind the engine tins and the short could be back there.

[Achto 26,500]

14 minutes ago, 953 nut said:

Have you substituted a new wire fir the old one going to the regulator "B+"? I think the wire travels behind the engine tins and the short could be back there.

 

I have not tried that yet. The B+ wire goes directly from the regulator, (which is mounted under the hood on the dash pedestal) to the ignition switch. It is mostly out in the open & doesn't appear to have any damage. The AC wires do go behind the tins, but I would think that if they were damages they would short out weather they are hooked to the regulator or not.  

 

 

[953 nut 51,487]

3 minutes ago, Achto said:

The AC wires do go behind the tins, but I would think that if they were damages they would short out weather they are hooked to the regulator or not.

Couldn't one of the diodes send 12 volts back to a short?

[cleat 4,936]

I had the engine tins off the 312 when I first got it for cleaning and to set the magneto to flywheel clearance (it was actually rubbing).

 

Put everything back together and it would not start.

 

Turns out I put the regulator plug wires around the wrong side of the choke linkage and it was stopping the choke from working properly.

 

Not really an electrical issue, just wires binding up a linkage.

 

Likely not your issue but just something to look at.

 

Cleat

[Achto 26,500]

45 minutes ago, 953 nut said:

Couldn't one of the diodes send 12 volts back to a short?

 

I believe that the only place that there would be a diode would be inside of the regulator/rectifier. There wouldn't be any on the stator, if there was it would not produce AC power. A bad diode in the reg/rec should have been corrected when I replaced that part. I thought about installing another diode in the B+ wire, but I think that the reg/rec will not produce DC power without seeing some DC power. An in line diode would not allow voltage back to the reg. 

 

Gotta admit, this is one of the strangest thing I've had to trouble shoot. I truly appreciate the ideas & comments, I'm trying really hard not to get locked in by tunnel vision on this one. You guys are giving me some great things to check & try.

Edited October 8, 2018 by Achto

[pfrederi 17,120]

Try running the coil + directly from the battery +.by a jumper.  Even if the charging system is doing something wierd or sucking up all the power at the switch the battery should provide constant power to the ignition.  (You will have to pull the jumper to shut her down.)

[WHX?? 46,681]

Here's that thread I mentioned. Probably won't help with the problem but an interesting if not humorous  read. Sure wish this member was still active

Rectifier-Regulator Autopsy from OLD Redsquare forum.pdf

 

Here another one that may or may not help IF the problem is electrical. Still not a bad idea keeping this on file. Stator business  info starts about page 21.  

07 - Engine Electrical Systems.pdf

 

This was out of that manual for a 15 amp charger

Edited October 8, 2018 by WHX21

[953 nut 51,487]

3 hours ago, Achto said:

should have been corrected when I replaced that part.

                Yes, I had forgotten you told us that you had replaced the regulator.             

[WHX?? 46,681]

Yup Richard, did it at the tractor show and thought problem fixed...charging looked good and voltages correct till extended? seat time. I say pull the tins and flywheel just to check things out. Would be interesting to see what voltages crop up when it does it's thing, possibly with a ac voltmeter clipped to to the stator. I am just not convinced this is a electrical draw problem. To stop a mighty 14 in it's tracks takes alot of power. Its just weird that unplugging the reg problem goes away. Note the very small resistance on the stator Dan .1/.2 ohms?? I would have thought that meter would have been able to read that small? 

OK the up side might mean more diagnostic seat time!

Edited October 9, 2018 by WHX21

[Achto 26,500]

6 hours ago, pfrederi said:

Try running the coil + directly from the battery +.by a jumper.

 

This is a great idea. I might even one up it by disconnecting the + wire on the coil & run the ignition power off of a separate battery all together. Thanks to @WHX21 I happen to have some small 12v batteries that will work great for this experiment.

 

3 hours ago, 953 nut said:

Yes, I had forgotten you told us that you had replaced the regulator.

 

No worries Richard.

 

1 hour ago, WHX21 said:

OK the up side might mean more diagnostic seat time!

 

[953 nut 51,487]

Just had a thought (not too often that this happens).     Could the problem be in the ignition switch? If it is occasionally shorting to ground internally at the "R" terminal that would also kill the ignition. Probably not because it only happens when the regulator is connected.

I like Paul's idea of a jumper to the coil.