416-8 slows down & dies after mowing for a while

[davem1111 2,030]

I recently sold a 1989 416-8 that I had done a "worker restore" on (cleaned up, repainted tins and wheels with rattle cans, flushed trans, fixed some wiring, etc.) to a friend who lives about 45 minutes from me. He started having trouble with it as he was trying to get some mowing done a day or two later.  This is puzzling. I ran the tractor around a bit, and when my friend picked it up his son drove it around for about 10 minutes mowing at my place. It did fine.  I hadn't run it this much before, because it didn't seem like I needed to.

 

Anyway, he told me that after about 20 minutes or so of mowing, it started slowing down (I'm guessing like the engine was just straining or starving for gas or something like that. But this tractor has a 12v aftermarket fuel pump, and the battery sat in an unheated garage for the winter, maybe recharged once or twice and it seemed fine but maybe the battery was dying or the charging system wasn't recharging it and the fuel pump was slowing down. This tractor has the original Onan engine, and it does smoke a bit on cold start but seems to have enough power, at least before the trouble starts.  

 

He bought a new battery, and he said it's reading like 12.5v or so when running - shouldn't it be much higher?  And it still does the same thing with a new battery so I think that's off the table. I'm thinking it's the charging system, or something is wrong with the engine that causes it to bog down after running for a while.

 

My friend is being quite understanding about all this, but he had moved from town to a place with a bigger yard earlier this year, and the grass is quickly getting ahead of him. I have a 1992 416-H that needs some work, so one option will be to swap them out, but I'm looking for any ideas as to what might be causing this problem first.  Thanks!

[Bill D 1,922]

Battery doesn't sound like it's charging.  Battery voltage should be around 14V when running.  Once the battery discharges enough the ignition will cut out.  Check the AC voltage into the voltage regulator, should be 40 VAC or more.  Check to make sure your voltage regulator is properly grounded.  Swap regulators if you have a spare and see what happens.

Edited April 21, 2023 by Bill D

[rmaynard 15,501]

Almost sounds like the vent on the gas cap is clogged. Ask him to loosen the cap and see what happens.

[Ed Kennell 38,196]

6 hours ago, Bill D said:

Check the AC

 

6 hours ago, rmaynard said:

vent on the gas cap is clogged

Two good suggestions that could cause the problem  and cheap easy fixes.

[953 nut 55,280]

7 hours ago, rmaynard said:

Almost sounds like the vent on the gas cap is clogged. Ask him to loosen the cap and see what happens.

      As gas leaves the tank a slight vacuum is created in the tank if there is no vent. Once the vacuum exceeds the ability of the fuel pump to pull gas from the tank the engine won't run.

Years back I had a Wheel Horse that was not charging it would mow for two hours each mowing for a couple weeks without any issues if I foregot to charge the battery so I wouldn't think the charging system is causing the problem.

[peter lena 8,632]

@davem1111 agree with others on possibilities , try this , run an alligator clip test wire from your battery cable ground bolt to one of the RECTIFIER BOLTS , corrosion / paint , frequently stops electrical ground assurance . tractor I  just sold , had many electrical , issues . after verifying poor function and grounding , made up a 10-12 gage wire , to that rectifier bolt down , solid regular charging . learned long ago to never count on original ground points . upgrade / refresh them , your amperage gauge will snap to attention . pete

[Lee1977 6,663]

Does that tractor have the 9 pin connector. I had to take the battery wire and the start wire out of mine when I got it.  

[davem1111 2,030]

4 hours ago, Lee1977 said:

Does that tractor have the 9 pin connector. I had to take the battery wire and the start wire out of mine when I got it.  

 

I'll have to get him to send me a picture, or wait till I can get over there.  Is this a connector between the ignition switch/console gauges and the engine? 

[davem1111 2,030]

13 hours ago, rmaynard said:

Almost sounds like the vent on the gas cap is clogged. Ask him to loosen the cap and see what happens.

 

Hadn't thought of that.  I think this one has a reproduction cap that I bought, which may not be properly vented. Thanks.

[davem1111 2,030]

I need to add here, that it might be something as simple as the throttle handle being a bit loose and gradually working its way down.  Something jogged my memory about that, and it seems like when I was working on this tractor it may have done that, but I tried a few things to get it to stay in place. New owner may not be check the throttle position and moving it back up if it slips.  

[Lee1977 6,663]

3 hours ago, davem1111 said:

I need to add here, that it might be something as simple as the throttle handle being a bit loose and gradually working its way down.  Something jogged my memory about that, and it seems like when I was working on this tractor it may have done that, but I tried a few things to get it to stay in place. New owner may not be check the throttle position and moving it back up if it slips.  

I clamped my throttle with big vicegrips to tighten it up, been working a couple of years.

[kpinnc 12,065]

17 hours ago, davem1111 said:

I need to add here, that it might be something as simple as the throttle handle being a bit loose and gradually working its way down. 

 

I put a 1/4 bolt and nylock nut through the pivot on mine. You just snug to set the tension, and you're good.