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post #1 of 15 Old 06-05-2019, 03:07 PM Thread Starter
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JD 425 hard starting cold, starts fine hot

I've been having a recurring problem with my 425 w/ Kawasaki FD620D motor, it will sometimes start cold, but the vast majority of the time, and it's getting worse, it will spit, sputter, backfire thru the exhaust, shudder and after so much cranking you'd think the starter would burn up, it'll finally start, even then sometimes it will quit and have to restart, and sometimes it will run fine. If you choke it, even for a second or two, it's flooded beyond belief, then a backfire thru the exhaust and repeat cycle. Warm, the thing runs like a banshee, never a problem, with plenty of power. Well, if you have this problem, I'd like to hear the fix.

For me, I checked the fuel shutoff solenoid and it was working. So, because I mow over 5 acres around the two houses I own next to each other, I decided not to fiddle with it, and I checked the plugs, looked fantastic, checked the valves, lash was good, and since it runs strong and fine when warm, and will start with just a blip of the key when warm, I surmised that fuel delivery on startup was the problem. I have two full sets of fuel pump/gas gauge setups that I had tried to no avail, both did the same cold start routine. Soooooo, I bit the bullet and bought a new carb from the local JD dealer and wooohooo! it seems to have fixed it big time.

Before i put on the new carb, of course it started right up with a blip of the choke. I only ran it for 30 sec or so to move it into the light. Changed the carb, and forgot I had the choke on so as to not drop anything down the carb throat, and it fired instantly. Choke off and it started right up. Let it set for 45 minutes, no choke, started right up instantly. So I think it's fixed, but time will tell. One interesting thing when I was looking at the old carb, the fuel shutoff now will not work. I tested it by putting it across a battery and no pull in. So maybe it was part of the problem, but the tractor shouldn't run at all with it not opening? right?

Anyway, if you've had this problem, I'd like to know if anyone ever nailed it down exactly. I haven't had time to do an autopsy on the old carb. I'd had it apart a few time monkeying with float levels to see if it made a difference, and it did not, so I just dunno.
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post #2 of 15 Old 06-05-2019, 03:11 PM
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Re: JD 425 hard starting cold, starts fine hot

It may have had a problem with the float sticking open.

I would suggest checking the oil level, to make sure it's still correct. If it's too high, then most likely there's fuel in the oil, and you should change the oil.
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post #3 of 15 Old 06-05-2019, 03:16 PM Thread Starter
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Re: JD 425 hard starting cold, starts fine hot

That's a good thought, but I keep a close eye on this thing, as it's my favorite tractor and I keep it mechanically top notch. The oil level is right where it was when I changed it and this thing, so far uses not oil and has 675ish hours. It's my third or fourth JD GT and I love the thing. I bought it used because it was the GT I always wanted but never seemed to find when the time came to buy one. I always found a real good deal on something else and couldn't pass up the deal. Well, this one happened along and I didn't even need a tractor, but since it's my favorite, I jumped on it, and sold my other one.
Anyway, I had checked the float and was convinced it was not fuel logged, but I'm wondering if I might have missed something there. As I said time will tell, but thanks for the reminder, it's always good to have more brains thinking on something like this.
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post #4 of 15 Old 06-06-2019, 02:06 PM Thread Starter
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Re: JD 425 hard starting cold, starts fine hot

Carb postmortem:
No jets plugged and very clean inside. There are 4 or 5 jets, can't remember. Let's see main jet, inlet jet, two air bleeds on horn and inlet needle seat. All clear and clean. Housing gasket looked good. Shutoff solenoid won't work with 9v battery, but resistance is 48 ohms, so I'll check with car battery later, but can't imagine it being the problem. The throttle and choke shafts are above the level or below the bowl, so no fuel could leak into the engine from them, they would leak air. Fuel could, I suppose, a leak from the main jet well thru the idle hole below the throttle plate over time, but there again, you would need vacuum to pull fuel thru the bypass, so I dunno. Needle valve looked good and I had previously adjusted the height in an attempt to alleviate the cold start problem, it was dead on with the manual. I did notice that the float pivot pin was pretty loose in it's hole, but this is pretty common, I really can't see it as a problem, as this is done so very little binding will occur. Fuel pickup tube in the main jet well was clean and clear, no problem there.
So far, the tractor with the new carb starts every time, instantly. But, for the life of me, I can't see anything in the old carb that indicates a problem. As I said earlier, I can't imagine the fuel shutoff solenoid being the problem, as it would simply stop fuel from entering the bowl. At that point using the choke would be no different than any other use of the choke, so flooding at that point wouldn't be any different?
The one thing that comes to mind is the needle and seat leaking through, although they looked perfect. If it were leaking through and you then choked it, you would be double dosing the engine, and that seems likely, but if that were the case I would think it would start without choking, but I dunno.
I'm stumped at what might have happened and am not going to claim victory until I've used the new carb a few weeks, but I KNOW it starts completely differently from the old carb. You know how you KNOW your tractor and how it acts, well it definitely starts better now, but why is a total mystery. I'm guessing if I had taken the time to clean and rebuild the carb completely it would have worked as well as a new carb, but didn't want to take the time.

Just went out and checked fuel shutoff solenoid and it is definitely bad. Will not pull in even though the coil shows 48 ohms. There's no way to check it for being grounded as we don't know the spec on resistance and the body is the ground. Sooooo, that's got to be at least part of the problem, but how in the world did the tractor run when warm???

Last edited by bchannell; 06-06-2019 at 02:48 PM.
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post #5 of 15 Old 06-06-2019, 06:48 PM Thread Starter
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Re: JD 425 hard starting cold, starts fine hot

UPDATE:
I rechecked the fuel shutoff solenoid and it's good. You cannot check it's function off the carburetor, as it's stem comes out too far from the magnetic coil for it to be able to pull it in. When mounted in the carb, it is slightly pushed back into the coil when at rest, allowing the coil to pull it in when energized. So it seems 48 ohms is about right for it's resistance.

Now back to square one, and no idea of what's wrong with the old carb.
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post #6 of 15 Old 06-07-2019, 08:45 AM
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My guess is your choke cable is stuck or needs adjustment. There may be enough thermal expansion or contraction to bind up the throttle plate on the carb or similar.


I am experiencing something different. I know when my 425 engine is fully warmed up and i shut off the engine, I can't move my choke cable and I definitely cannot move the little arm / lever that controls the throttle / intake plate. In general, it is better to start a warmed up tractor with the choke closed.

When the area is cooled, i can easily move everything. I have to train others who mow the grass on how to start the tractor from a cold startup and from a warm startup.
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post #7 of 15 Old 06-19-2019, 12:41 PM Thread Starter
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Re: JD 425 hard starting cold, starts fine hot

UPDATE 6/19/2019
Well, I finally figured it out. There was NOTHING wrong with the carb. After the switch, I just got lucky and it started most of the time without hassle, but today, after setting for three days without being started, it simply would not start, and for the first time since the new carb was installed, started backfiring thru the muffler with raw fuel coming out. That should have been my original clue, but you know how it is, you get sidetracked. I thought raw fuel was likely a carb problem, but the new carb also flooded easily. My thinking also was sparked by the old carb not having any visible problems upon postmortem. So, I got to thinking, starts fine hot, not cold, floods easily, and finally, when I checked it cold and no start, it also had no spark....hmmmmm, bad coils, no can't be runs good hot. Then it hit me, whats different between hot and cold...the speed it turns over when starting. A warm loose, well oiled engine will spin faster than a cold, less oiled, stiff engine. Slow engine spin at start, no spark...STARTER. A weak starter could spin a cold, stiff engine just slightly slow enough to get no spark. As luck would have it, the parts hoarder I am, I had bought a used starter off ebay for a song. So, I thought it's worth a try. I switched them out and when I went to start it after the switch, I could tell you immediately it was the starter, it spun much, much faster, almost violently, when the old one sounded like a '60s mopar starter. It started so fast I couldn't get the key released fast enough, and it's never done that with the old starter.
After reflection, that's why it flooded so easily, cranking with the choke on and no spark. After enough cranking and getting oil flowing then it spun JUST fast enough to get it started, or a huge backfire out the muffler, and then it starts, but that would take quite a bid of cranking. So much so, that I was worried about overheating the starter. It all makes sense to me now, so I hope this will help some of those online having similar problems.
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post #8 of 15 Old 06-19-2019, 02:19 PM
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Re: JD 425 hard starting cold, starts fine hot

I had a slow starter for one of my Kohlers. I swapped it out and then took it apart and the upper and lower bushings were very dry and everything else was in great shape. I lubed it up and now it's just as fast as the newer one so now it's back on the motor in use.
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post #9 of 15 Old 06-19-2019, 02:22 PM
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Re: JD 425 hard starting cold, starts fine hot

Also, some of the starters on the Kawasakis have 2 of the brush springs made out of very thin gauge wire. They loose their tension due to overheating or rust and the starter will spin slower. I use 2 of the stiffer springs out of parts starters in place of the soft springs and the starters work fine.
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post #10 of 15 Old 06-19-2019, 08:08 PM Thread Starter
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I did postmortem on the starter too. Dry, as you said, bearings seemed slightly loose, but no rub marks on roror or stator. Brush springs were fine. I'll clean it up and lube it and save as a spare. Didnt have time to finish it.
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post #11 of 15 Old 06-19-2019, 08:12 PM
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Re: JD 425 hard starting cold, starts fine hot

One of my starters will chatter when the lower bushing gets dry. It's really a poor design as the bottom of the bushing is open. You can see the bottom of the shaft. It does make it easy to push some grease up into the bushing with your finger.

On the starters with a closed end arrangement I often drill a small hole above the bushing area so I can squirt some oil in there.
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post #12 of 15 Old 06-19-2019, 08:29 PM Thread Starter
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I like the idea of drilling a hole in the closed end. I think I'll give it a try on my rebuild.
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post #13 of 15 Old 06-19-2019, 11:45 PM
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Re: JD 425 hard starting cold, starts fine hot

This was on a Briggs starter but you get the idea. Doing with with the bottom plate off the starter is better than just keeping your fingers crossed !!

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post #14 of 15 Old 07-19-2019, 06:07 PM Thread Starter
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Re: JD 425 hard starting cold, starts fine hot

Well, this is a bit embarassing, but the starter was not the issue, my hard head was. It was the ignition delay module. I just couldn't imagine it being bad, because it delayed as it was supposed to and never until after all the "faux fixes" stalled after it started. Everyone of the posts about the delay module said the tractor would stop at some point after starting, and mine never did. Once it started I could use it all day, and it would start instantly. Well, I finally caught it not firing when trying to cold start it, and I knew the module was probably to blame. As near as I can tell, it was, at least some times, delaying upon cold start. I can't imagine how this could be, but after cranking it would eventually spark. Anyway, put a new one on, and now I can use the choke as normal, without flooding, and it starts every time hot or cold. I've now used it for two weeks or so and it starts like a new tractor, so I'm admitting, I should have listened to all the posts about the delay. For $20 or so from the dealer, I'll change it first the next time i'm in any doubt.
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post #15 of 15 Old 07-19-2019, 06:20 PM
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Re: JD 425 hard starting cold, starts fine hot

The planned obsolescence engineers at JD are high 5ing one another for another sale.
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