4720 keeps blowing ignition fuse

[Karl2]

This is a follow-up to this thread here:

http://www.tractorbynet.com/forums/john-deere-owning-operating/142452-4720-wont-crank-both-power-2.html

Now that I have pinned down the issue as an ignition problem rather than PTO safety switch failure or computer glitch I thought it would be simpler to start a new thread to address this more common problem. Members should only read the other thread if they enjoy reading about somewhat clueless and slightly tedious troubleshooting sequences that lead to the pinpointing of a specific problem.

Simply put, my ignition fuse keeps blowing every time I attempt to start the engine. Yesterday I had been using the tractor for about 4-5 minutes when it suddenly died and would not crank, not even a click, even though everything else worked. Symptoms were the same as attempting to start with PTO engaged, but the PTO was not engaged. After many hours of troubleshooting I finally noticed that the ignition fuse keeps blowing when I attempt to start the engine. What would be the most common cause of this?

If it's of any help it was unseasonably hot up here yesterday, about 85 degrees and the tractor sits outside in the sun all day. I've only used this tractor in wintertime before so I'm not familiar with heat related issues that may affect it. I used AC in the cab but at a low blower setting, I would say cab temp before I used the tractor was at least 100 degrees. Could this affect wiring?

 

[Karl2]

Jeez this is getting frustrating, I know I can fix this with some patience and caution but my immediate problem is to simply get the tractor off my driveway's end and back near the house where I can more effectively work on it.

I parked the tractor in such a way that it blocks entrance to the driveway, not too brilliant but I wasn't expecting it to die on me there. Now my wife's car is parked on the side of the road and I can't get my pickup truck out of the driveway, the presence of deep ditches forbids driving around the tractor. We tried pulling the tractor with my truck (a 4x4 F150) but the driveway is a slight grade and gravel, so that was a no-go. All 4 wheels on the truck were skidding and the tractor actually pulled the truck back about 10 inches when I released the park brake with the wife driving the truck. Never realized until now just how heavy this "compact" tractor really is! Only way the truck can pull it is when it's loaded on a trailer and even then, truck balks.

Standard tow would not touch it, I was told I needed a heavy-lift tow and since we live in the middle of nowhere (or so the tow guy said) they want to charge me $700 for a 600-foot tow (length of the driveway), no friggin' way I'm paying that. Nearest JD dealer is 3 hours away and I know by experience a service call will run me even more. I don't think this fuse thing is a serious issue and I'm pretty confident I can fix it, but not where it's sitting now.

Since this is a diesel I am now seriously toying with the idea of bypassing the ignition to get the engine going long enough for me to drive it back to the house. I know it can be done, just not too sure what exactly has to be done to juice up the starter motor, I suspect it involves screwdrivers and sparks as I recall my late Grandpa doing this routinely with his tractors and dozers.

 

[Karl2]

Hmmm... not that much info on the Net on how to bypass-start this type of starter, but plenty of info about the dangers of bypass-starting tractors that are in gear and explanations on why modern tractors have a seat switch that prevents starting while not in seat.

I am aware of the hazards but but my tractor is hydro and JD is confident enough that hydro tractors won't run the operator over that they let us start them even when we're standing alongside the tractor and obviously not in seat, something I do routinely in winter when I want to warm up the cab without having to sit on a cold seat. Apparently other types of tractors won't let you do that and for good reason, judging from the multitude of accident reports I stumbled upon that involved operators bypass-starting tractors that had been left in gear. I understand some people abuse bypass-starting on problematic machines instead of fixing them, not a good idea.

I don't think it's possible for a hydro tractor to run someone over after bypass-starting it unless it's on a grade in neutral with park brake not engaged, in which case it can run you over even without engine running anyway. But to play it safe I nonetheless intend to bypass start my tractor with shifter in neutral and park brake locked to avoid unpleasant surprises. Don't really have a choice with the park brake anyway, if I disengage it while in neutral the tractor will roll down the slight grade and sit in the middle of the main road. To avoid any risk of accident the park brake's been locked since yesterday, chocks wedged underneath the wheels and shifter in A position.

 

[mfreund]

You should be able to pull the tractor in neutral. If not that is one steep drive or traction is bad.

You need a service manual for the tractor to effectively find out what is on that circuit. I know, if only!! I would pull the glow plug relay and see if the fuse blows. It is imposible to know what is on the circuit,but something has a dead short to ground. I wish I had a manual to help!!

 

[jenkinsph]

Karl you have my sympathy for what is is worth


You may have to weight the truck down to get the tractor towed back up the
driveway, I would do that first. You may find the tractor is easer to move if the range selector is disengaged by moving it between b and c positions.

If you know how to use a vom meter you may find the problem.

One question I have is does it blow the fuse if the ignition is in the run position or the starter position?
Much simpler problem if the start position only.



Steve

 

[jd110]

These tractors require more than cranking the engine to start. There is also afuel solenoid to energize. That will get the engine running. But it still wont move unless you power up the E-hydro computer. A better solution would be to tow or drift the tractor to a better location. If you put the range lever in neutral and release the brake, I would think your truck could tow it somewhere out of your way. There are several components pwered by your blown fuse. Among them are, Seat switch, instrument panel mode switch, fuel gauge, park brake switch, rear pto switch, mfwd switch, mid pto switch, and air filter restriction switch. Since it quit after you got off the tractor, I would start with the seat switch and park brake switch areas since these switches cycled when you got out of the seat and applied the brake. Try unplugging one of these components at a time until the fuse no longer blows.

 

[Karl2]

Karl you have my sympathy for what is is worth


You may have to weight the truck down to get the tractor towed back up the
driveway, I would do that first. You may find the tractor is easer to move if the range selector is disengaged by moving it between b and c positions.

Loaded the bed as much as I could, however that truck experienced transmission issues a few months back so I don't want to push my luck. Will try with selector disengaged tomorrow though, God bless the home office I won't be needing to go out and fortunately my wife can still use her car to go to work as it's not trapped.

If you know how to use a vom meter you may find the problem

Can do.

One question I have is does it blow the fuse if the ignition is in the run position or the starter position?

Starter position only

In the run position all the usual bell and whistles work as usual. In fact I tested every single electrical device (lots of those in a cab I noticed) and all work fine, battery power delivery appears to be in perfect shape. Tested all fuses by rotating them through the sockets of matching amperage and operating equipment hooked to the corresponding circuits, all worked fine except those plugged in F5 (ignition 15A) which kept blowing when the key was turned all the way to the right (starter position).

I also tested the 4 main relays, which are all of same value, by removing them and connecting each one in turn to the K4 relay socket (rear work light circuit) and turning on said light, which won't work if a faulty relay is used (I think). In any case it wouldn't work when there was no relay in the socket and worked fine with any of the four relays plugged in.

 

[Karl2]

These tractors require more than cranking the engine to start. There is also afuel solenoid to energize. That will get the engine running. But it still wont move unless you power up the E-hydro computer. A better solution would be to tow or drift the tractor to a better location. If you put the range lever in neutral and release the brake, I would think your truck could tow it somewhere out of your way. There are several components pwered by your blown fuse. Among them are, Seat switch, instrument panel mode switch, fuel gauge, park brake switch, rear pto switch, mfwd switch, mid pto switch, and air filter restriction switch. Since it quit after you got off the tractor, I would start with the seat switch and park brake switch areas since these switches cycled when you got out of the seat and applied the brake. Try unplugging one of these components at a time until the fuse no longer blows.

You may be on to something, prior to driving down to the main road I had played with the seat adjustment compressor until it bottomed out, maybe this damaged the seat switch and caused a short. I guess I can test this possibility by disconnecting the seat switch from the harness behind the seat, shorting the connector, and attempting to start? If the seat switch is faulty and causing the problem then bypassing it should get rid of the issue I suppose.

If that doesn't work, ideally I would proceed by bypassing every switch hooked to that circuit one after the other in order to eliminate each one as the source of the problem until the only switch left is the ignition switch itself? Do the switches you mention constitute the full list of switches on the F5 circuit?

So even if I managed to bypass-start the engine I still wouldn't be able to move the tractor? Wouldn't leaving the key in the "run" position allow computers and controllers to be powered?

 

[jenkinsph]

Karl,
If the fuse only blows in the start position then disconnect and separate the leads to the starter solenoid. Then turn the key to see if the fuse still blows, if it does not then you likely have a bad solenoid, if it does blow you have a
problem in the dash or wiring from start terminal to the solenoid. I don't have my manual yet for my tractor so I can't tell if the safety switches are in series with the starter circuit.

Another thing you may try is if the fuses don't blow in the on position then with the starter lead removed from the solenoid you may be able to start the tractor if you hot wire it.

Since most of these safety devices will stop the tractor while running I would expect them to be upstream in series with the ignition circuit. Placing them upstream means they can prevent starting as well as stopping the engine. The seat switch will diengage the ehydro but doesn't necessarily stop the engine.

My hunch is you have a short between the ignition switch start terminal and or the solenoid switch.



Steve

 

[Karl2]

By starter solenoid are you referring to the fuel shutoff solenoid? If there's a starter solenoid it must be built into the Bosch-made starter which may explain why it's not listed on the JD parts list...

But I can still test the starter motor by disconnecting it and see if the fuse still blows, can I? I doubt the starter would be at fault by who knows.

 

[AKfish]

By starter solenoid are you referring to the fuel shutoff solenoid? If there's a starter solenoid it must be built into the Bosch-made starter which may explain why it's not listed on the JD parts list...

But I can still test the starter motor by disconnecting it and see if the fuse still blows, can I? I doubt the starter would be at fault by who knows.

The engine starter has a solenoid, too. jd110 and jenkinsph are both saying the same things - more or less.

Troubleshoot by process of elimination. If you disconnect the starter and then engage the ignition key and the fuse blows - the problem is upstream of the starter. Seat safety lockout, etc. That was jenkinsph point.

jd110 suggested to work the problem in a similar manner. Eliminate the seat as the problem, eliminate the park brake as a problem, etc.

I think you've already "put your butt on the problem". Cranking the air seat down.... it might have gone down too far!

Keep us posted.

AKfish

 

[Karl2]

The engine starter has a solenoid, too. jd110 and jenkinsph are both saying the same things - more or less.

Yes I realize the starter has a solenoid but on this model of starter it is either not exposed or very well camouflaged. Speaking of which, in the New Holland forum I found someone who has the same problem with his late-model TN65 and is able to bypass-start and operate it. However even though he also has a Bosch starter his has the solenoid in plain sight. That said, I don't intend to attempt bypass-starting my tractor anymore. If I need to I will test for starter malfunction by simply disconnecting it and see if the fuse still blows when I turn the key to the start position. However I suspect the problem is upstream so I'll troubleshoot there first.

Troubleshoot by process of elimination.

It finally stopped raining so I'm getting back to it. The first procedure I intend to do is to visually inspect wires under dash panels for obvious damage, could save me a few fuses as I'm running low on them and need to resupply.

Next I will test all NSS switches I can think of starting with the seat switch. Since I don't have a service manual yet I may miss some but common sense should help. If I were an ignition I would look for these before allowing the starter to crank:

-PTO switch: must be off.
Human testing action required: bypass PTO switch and see if fuse still blows. Not too sure how to do that yet but info about how to bypass a three-pronged switch must be available on the Net somewhere.

-Hydro pedals: must not be jammed in travel position.
Human testing action required: 1) make sure pedals and sensors are not jammed and see if fuse still blows. 2) find and bypass switch, proceed as with the other NSS switches

-Seat switch: no check required for starting (hydro tranny) but must be depressed to maintain ignition when rear PTO is on.
Remark: even though the seat switch position is normally not relevant to the starting sequence on this tractor model, it is possible that a malfunction in said switch could be causing the fuse to blow
Human testing action required: test switch using bypass procedure.

Note: I suppose it is possible that the next two items' safety feature is controlled by the PTO NSS switch rather than their own.

-Park brake: no check required for starting (hydro tranny) but must be engaged to maintain ignition when rear PTO is on and seat switch not depressed.
Human testing action required: find and test switch (if present) using bypass procedure if feasible.

-Transmission position lever: no check required for starting (hydro tranny) but must be set on neutral to maintain ignition when rear PTO is on and seat switch not depressed.
Human testing action required: find and test switch (if present) using bypass procedure if feasible.

I don't know if other controls have NSS switches but I think the above are the primary suspects. Does this make sense?

 

[Karl2]

Hot dang it starts!

Bypassing the seat switch shut off the PTO indicators and the tractor started right away without blowing the ignition fuse

BUT

as soon as the engine cranked I heard another fuse pop. This time it's the F11, a 20A fuse labeled "Air Seat/Diverter Option", and an ominous hot circuit aroma wafted up prompting me to cut the engine at once

I think I know the source of this problem. I used a tiny computer-grade alligator wire to short the female connector behind the seat that connects to the cable leading to the seat switch. I suspect this wire has too much resistance for the circuit causing it to overheat and pop the fuse. Is there a preferred method and proper wire to bypass the seat switch without risking anything catching fire while driving the tractor back up the driveway?

I don't have any spare fuses above 15A but I think I can do without seat control and diverter for the 600-foot drive. I'm a little puzzled as to why the seat compressor and diverter circuit would be affected by the seat switch but obviously it is in some way.

 

[AKfish]

Congrats!! You're darn near home.. er, back up the driveway! Don't know how the air seat ties into the safety presence switch but it sounds like they have a shared circuit.

Is your dealer any help on this? Call from your cell and have the tech walk you thru a workaround on the seat switch..? I think I'd call 'em anyway and let them know of the problem and see if they might have any info from Deere regarding this issue. Your tractor might not be the ONLY one to have this happen!

AKfish

 

[Karl2]

Congrats!! You're darn near home.. er, back up the driveway! Don't know how the air seat ties into the safety presence switch but it sounds like they have a shared circuit.

I fashioned a jumper from a piece of 12 gauge solid copper wire to replace the alligator wire and that did the trick, no more fried wire smell in the cab and engine starts like a champ so I was finally able to bring the tractor back to the house and driveway is back in business.

I was not at ease having to leave the tractor practically on the side of a main road in plain view of passing motorists . We couldn't see it from the house and I've read threads on this forum about bozos tampering with or even attempting to steal stranded tractors while they were out of view from their owners.

So most of the ordeal is over but the F11 fuse still keeps popping so I can't use the diverter valve or adjust my seat. Not a big deal since I only use the diverter valve to operate the rear snowblower chute with the SCV in winter. As for the seat however it is completely "deflated" at the moment and while that's fine driving at 2 mph on a smooth surface I can't imagine myself not doing anything about it very soon.

Is your dealer any help on this?

Not really, but I can't blame him. I purchased this tractor used through our local Massey-Ferguson/Kioti dealership (MF has always been very popular with farmers and snow removal operators in these parts), he cannot offer official support for other brands but will usually fix most makes. It's expensive though. The nearest JD dealership is three hours away and will send a tech if I really insist, but ignores my orders for parts. There's a closer -and much nicer- JD dealership across the border in Quebec but they are not authorized to send techs to Maine. I do however purchase most of my JD parts from them in person, there is no Customs duty on parts because I have a commercial business license to prove I need them for work purposes. Most JD owners in the area do the same.

Your tractor might not be the ONLY one to have this happen!

If you're talking about the seat compressor/diverter issue, I wouldn't bet on that just yet

As for the starting failure/PTO indicators lit problem then no, I'm not the only one who had to deal with this. From what I could gather on the Net it does happen to many tractor owners, but the causes are varied and usually spread among various NSS failures. On hydro tractors both the seat switch and PTO switch are cited very often.

As for the reason behind the F11 popping fuse my current tentative theory is that perhaps there's a system that faults when the seat switch wire is shorted, as a deterrent to those tempted to permanently bypass the switch. I believe that replacing the faulty switch should solve this problem. I guess a trip to Quebec is in order for later this week!

 

[jenkinsph]

Karl,
Glad you got it figured out but keep us informed as to how this finally plays out. I would like to know of any other quirks you run into.



Steve

 

[ddivinia]

Is your tractor still under warranty?

D.

 

[Karl2]

I would like to know of any other quirks you run into.

Well! I am about to give the tractor a thorough checkup as it's creeping up towards the 1,000-hour mark (986 at the moment) so I'm likely to run into a few trouble spots. This morning I completely removed all dash panels (had to remove steering wheel as well) and looking at the wiring I noticed some wires had been taped. It doesn't look like a pro job so I suspect former owner did a few mods that may be interfering with proper operation of the electrical system. The dealer had showed me a picture of the tractor shortly before he sent someone to pick it up upstate and I had noticed that 4 extra work lights and a large three-beacon rack had been installed on the cab but these had been removed prior to delivery. Such equipment requires some fiddling with wiring and it may not have been done properly.

When I saw this I decided a complete check-up was in order to see if further owner mods have been performed. I would also like to get rid of the Error 8 error message (throttle sensor) which has been there ever since I got the tractor. This is an extremely common issue apparently and while it does not interfere with operating the tractor, it disables the anti-stall feature, and since I paid 30K for this used machine I would appreciate it if all features worked.

Ideally I would also like to fix the fuel gauge but that's probably hopeless unless I replace the whole instrument cluster/computer, and I am told the fuel gauge on a new cluster is likely to fail as well.

 

[ddivinia]

Well! I am about to give the tractor a thorough checkup as it's creeping up towards the 1,000-hour mark (986 at the moment) so I'm likely to run into a few trouble spots. This morning I completely removed all dash panels (had to remove steering wheel as well) and looking at the wiring I noticed some wires had been taped. It doesn't look like a pro job so I suspect former owner did a few mods that may be interfering with proper operation of the electrical system. The dealer had showed me a picture of the tractor shortly before he sent someone to pick it up upstate and I had noticed that 4 extra work lights and a large three-beacon rack had been installed on the cab but these had been removed prior to delivery. Such equipment requires some fiddling with wiring and it may not have been done properly.

When I saw this I decided a complete check-up was in order to see if further owner mods have been performed. I would also like to get rid of the Error 8 error message (throttle sensor) which has been there ever since I got the tractor. This is an extremely common issue apparently and while it does not interfere with operating the tractor, it disables the anti-stall feature, and since I paid 30K for this used machine I would appreciate it if all features worked.

Ideally I would also like to fix the fuel gauge but that's probably hopeless unless I replace the whole instrument cluster/computer, and I am told the fuel gauge on a new cluster is likely to fail as well.

Do you have the service manual? The troubleshooting section is rather good.

I had to replace my cluster, but it was under warranty.

I have not heard of the fuel gauge going out.

How old is it? Maybe it is still under warranty? The new ones have a longer warranty. Used to be 2 yr 2K hours, now it is 3 year 2K hour.

D.

 

[Karl2]

Is your tractor still under warranty?

Unfortunately not even though it's less than 3 years old. I bought it used and the warranty is not transferable.

It's not a major issue for me though. I consider troubleshooting and fixing the tractor myself as a hobby ever since I discovered that tractors are designed to be self-maintenance friendly and that major failures due to defective parts are quite rare in first-tier brands especially on diesel models. Many people don't realize there are resources available that can make them quite proficient at fixing their own machine provided they like doing such work and spend a lot of time operating their tractor. This is imperative if one is to acquire a "feel" of what the machine does and how it does it, and greatly facilitates troubleshooting.

Something that also helps me is the fact that even though this tractor will log at least 600 hours per year most of these occur during winter leaving me with plenty of time to learn my way through the machine's maintenance during spring and fall when working outdoors is most pleasant. That's how I learned how to maintain and fix my 1970 LeMans myself, as well as my motorcyles both of which I completely rebuilt two years ago, including engines. After I'm done with the tractor I'm restoring a vintage 1974 Honda CT70, the legendary small trail bike, to mint condition. I got one when I was 12 and never looked at a moped again. This one will be a gift for my daughter who'll be turning 13 in August, to replace her wimpish scooter. When she sees pictures of me long ago with that bike she says she wished Honda still made them. Well Daddy will "make" one. Parts were hard to find and often expensive but I got all the ones I need for the project.

I can't find my way through my F150 or my wife's Toyota Sienna though, modern vehicles may as well be from Mars as far as I'm concerned. It's not because I'm particularly old (I'm 45) but today's cars have what I call "turboloid molecular engines" meaning they don't make a whole lot of sense to me, and I am a computer programmer by trade!

Compared with that the tractor is a hobbyist mechanic's dream.