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 | benfranklin
Join Date: Jul 2003 Posts: 12 michigan 
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2003-04-03 52521
Tech/diagnostic question: I have a 790 w about 100hrs. Started it up, let it run and after about 10minutes it quit. It cranks now but won't fire up. red line is not up in the fuel bowl, tank is full. I do not get the "clicks" I usaully get when I turn the key to first position either.
Battery seems good. Whatdayathink ?
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 | DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada 
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2003-04-03 52526
Check fuses? ....
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| benfranklin
Join Date: Jul 2003 Posts: 12 michigan
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2003-04-03 52534
well, that was a good sugestion because it appears I do need a new 3Amp. However, in the process of checking I discovered that the fuse identification chart in the manual is not the same as the actual box on the tractor - meaning that the book lists right side postions as 1-6 and left side as 7-12. The actual box right is 1-5 and left is 6-10.
In other words the lowest left slot in the book is ID'd as H/7 but on the tractor it is 6 ????? The 3Amp that blew, the book says, is for the "postion indicatior" but indicates a 10Amp in that position (second up left/frm bottom. Boy if there's a JD mechanic out there maybe he can clear this up. In the meantime I'll get a new 3Amp ....
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| Roy Jackson
Join Date: Posts: 1
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2003-04-04 52561
No "click" when you turn the key? Sounds like one seriously dead battery. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2003-04-04 52565
I wonder if the click that isn't there has something to do with the pre-heaters. I don't know if 790's are indirect injection engines with glow plugs, but even a direct inject engine that uses a manifold pre-heater might be hard to start without some pre-heating. ....
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| benfranklin
Join Date: Jul 2003 Posts: 12 michigan
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2003-04-04 52569
Checked the battery out first and it seems fine - even the water levels were right. I did at first have the corrosion problems spoken of early on but fixed that too 6 months ago.I have a list of questions for dealer - including a proper schematic of the fuse box. As often happens there can be change from publication to on board equipment.My third tractor (IH and Ford) and this kind of thing just seems to go with the machines. I do wonder why the fuse blew ??? ....
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| DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada
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2003-04-04 52575
I am guessing the fuse controls a fuel shutoff solenoid. Sometimes they just go with no explanation. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2003-04-05 52601
MarkH's comment jogged my memory. An archive search on 'start' will find a previous discussion about 790's and fuel shut-off solenoids. There's not a whole lot of info there but a 3A fuse does sound like the shut-off and probably the problem as well. If so, I wonder how the manual writers got from fuel-shut off to position indicator (throttle position maybe). I keep forgetting about these solenoids. The wouldn't be too good for my Ford since it came before self-bleeding fuel lines and the Ford is very particular about air in the lines. No fuel would make it even harder to start than no heat.
If replacing the fuse doesn't do the trick, my recollection is that fuel shut-offs aren't hooked in to the rest of the safety interlock system so that simplifies trouble-shooting a bit. Besides, safety switch problems usually mean that it won't crank.
It is hard to track down electrical problems without a wiring diagram but a trick I learned with my cartridge fuses is to check for voltage on each side of a fuse on the holder contacts. I once found a dirty fuse holder that way. It'd be tougher with plug-in fuses but it might be possible to get a VOM on the contacts of a partially plugged fuse. That might not provide the whole answer but at least you'd know voltage was getting to the fuse.
....
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