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John Deere 790 fuel shut-off solenoid failing

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bantam
Join Date: Apr 2009
Posts: 3 Canton, OH
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2009-05-11          162657

My JD 790 failed, or appeared to fail, the fuel shut-off solenoid. With the key in the "on" position I could manually press in the solenoid plunger (with the solenoid removed from the fuel injector pump of course) then re-install the solenoid and the tractor would run. However, if I shut off the tractor and then tried to re-start the solenoid would not retract. So, the solenoid cold hold the plunger in if I manually pushed it in, but it couldn't pull the plunger in on its own. Long story short, I bought a new solenoid and within a week i am having the same problem. Surely the second solenoid did not fail in a week without some secondary cause. Did neither solenoid fail and I'm not pulling enough current from the ignition? What would make two solenoids fail, if in fact they have both failed? Thanks in advance for any help.

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John Deere 790 fuel shut-off solenoid failing

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2009-05-11          162660

I'd be surprised if you had 2 bad ones in a row.

In fact, it's been my experience that they rarely go bad, new or old.

I'd be looking carefully at the wiring to the solenoid itself, it doesn't take much corrosion, particularly on the ground wire, to cause the solenoid not to function properly.

Best of luck. ....

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John Deere 790 fuel shut-off solenoid failing

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jdgreen
Join Date: Jul 2003
Posts: 232 Maryland
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2009-05-11          162678

My guess is the solenoid timer delay module has failed. The timer supplies current to the "pull-in" windings for a brief time and then the "hold-in" windings keep it engaged. If the "pull-in" windings are energized too long, they will fail. As you have determined, the "hold-in" windings are still working. The timer part number is M803344. It is an expensive part. You might want to have your dealer diagnose it to be sure. ....

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John Deere 790 fuel shut-off solenoid failing

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bantam
Join Date: Apr 2009
Posts: 3 Canton, OH
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2009-05-12          162689

Thanks for the replies. I priced out the solenoid timer - it is $173. The fuel shut-off solenoid I previously replaced, and is burned out again, was $150. The dealer told me the timer should make the voltage should drop from 12v to 6v after about 10 seconds. I will put a volt meter on the hot to the fuel shut-off solenoid to verify whether the voltage drop occurs. If it doesn't I guess it's safe to assume that the problem is with the timer and that it will need replaced along with purchasing another fuel shut-off solenoid. Thanks again. ....

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John Deere 790 fuel shut-off solenoid failing

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djohns
Join Date: Aug 2010
Posts: 2 Prince William, Virginia
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2010-08-02          172749

I'm having the exact same problem with my John Deere 4600. I wonder if its the same set up as the 790? Was it had to fix? ....

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John Deere 790 fuel shut-off solenoid failing

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bvinduck
Join Date: Oct 2006
Posts: 25 Duck, NC
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2011-03-20          177478

I have a JD 4600. I have had several problems with my fuel selonoid: oil gets into it- next it will not start until I clean the oil out. I have asked dealer about it. They seem to think its not a JD, in that, they have not heard of this problem- will you are the 8th person I believe is having the same problem. I would like JD to fix this problem- admit there is a problem. I'm tried of cleaning out this fuel selonoid! Please let me know your thoughts. ....

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John Deere 790 fuel shut-off solenoid failing

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wuntun
Join Date: Mar 2011
Posts: 5 United States georgia
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2011-03-25          177603

I have a few of these solenoid Switch FOR YANMAR 119653-77950 for sale. They are the same as woodwards,(JD supplier) purchased from the same company. These are new, $108.32 each and free shipping in United States. Actual shipping anywhere else. Email or pm if interested. ....

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John Deere 790 fuel shut-off solenoid failing

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randywilliam
Join Date: Apr 2011
Posts: 6 Blacksburg, VA
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2011-04-20          178066

JD 4400- same problem, oil gets into the fuel solenoid. Don't think it's an electrical problem because when I remove the solenoid and force the oil from the plunger, the tractor always cranks. Have replaced the solenoid and still have the same problem. Don't understand how oil could even get to this solenoid. Is there a bad seal somewhere? I had this tractor 4-5 years before this started happening. Any ideas? ....

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John Deere 790 fuel shut-off solenoid failing

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wuntun
Join Date: Mar 2011
Posts: 5 United States georgia
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2011-04-20          178085

Your fuel stop plunger seal cavity is leaking oil. Probably not very much, but enough to fill the cavity over time and oil-lock the solenoid.(there is no built in oil drain) This problem is some what expensive to repair, but a cheap alternative (under $20)is available that you can do yourself. 1/8 tube adapters and 1/8 tubing from inj. pump to oil pan. Oil is not lost, only returned to pan, no oil in cavity means no oil in solenoid. Problem solved. ....

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John Deere 790 fuel shut-off solenoid failing

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harvey
Join Date: Sep 2000
Posts: 1550 Moravia, NY
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2011-04-21          178087

Randy I had the same problem on the 4400 and I'd take the selonoid off clean the plunger and it would work for a couple 4 weeks. The plunger with some oil is not the problem.
If the plunger will pull in it will displace the oil in it.
You need electric to get it to pull in.
JDGREEN posted the solution above for the 790. I would pay attention to it.

I battled mine for a couple years. JDGreen posted what to fix I got that do dad electrical thing and have not had a problem in a year and a half or more. My part was $5. I think he posted the part for yours to solve your problem. ....

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John Deere 790 fuel shut-off solenoid failing

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bvinduck
Join Date: Oct 2006
Posts: 25 Duck, NC
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2011-04-21          178091

Can you or wuntun give me a little more detailed information on fixing this problem? I would GREATLY appreciate it. Thanks ....

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John Deere 790 fuel shut-off solenoid failing

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randywilliam
Join Date: Apr 2011
Posts: 6 Blacksburg, VA
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2011-04-21          178093

Harvey, thanks for your reply. You say the part was $5. Could you give more details on the part number and how to install it? Thanks ....

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John Deere 790 fuel shut-off solenoid failing

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harvey
Join Date: Sep 2000
Posts: 1550 Moravia, NY
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2011-04-21          178094

re: John Deere 790 fuel shut-off solenoid failing???

Randy this was posted by JDGREEN earlier, read the entire thread. My guess is the solenoid timer delay module has failed. The timer supplies current to the "pull-in" windings for a brief time and then the "hold-in" windings keep it engaged. If the "pull-in" windings are energized too long, they will fail. As you have determined, the "hold-in" windings are still working. The timer part number is M803344. It is an expensive part. You might want to have your dealer diagnose it to be sure.

JDGreen Posted a different part to fix mine. The 4400 and 790 are different parts.

....

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John Deere 790 fuel shut-off solenoid failing

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randywilliam
Join Date: Apr 2011
Posts: 6 Blacksburg, VA
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2011-04-21          178095

But if this timer delay module was bad, why would it work sometimes and not other times? On any given day, there seems to be about a 50/50 chance that the solenoid plunger will retract when the ignition key is engaged. That seems unlikely, if the problem was strictly electrical. ....

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John Deere 790 fuel shut-off solenoid failing

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harvey
Join Date: Sep 2000
Posts: 1550 Moravia, NY
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2011-04-21          178104

Can't answer the why. Mine there was no ryhme or reason when it would or wouldn't start. So I'd pull selonoid and it would start. This went on for a couple of years. I finially did what was suggested to me and not one issue since.

I swore up and down it was the oil I could pull the selonoid right now and there would be oil in the plunger based on pulling it countless times. I carried little 10mm combo and could pull and put back in 15 minutes. Worse part was burning hands and fingers on hot parts. The do dad fixed it.

My point the resident, very knowledgable, JD guy has nailed it for many. ....

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John Deere 790 fuel shut-off solenoid failing

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jdgreen
Join Date: Jul 2003
Posts: 232 Maryland
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2011-04-21          178111

Randy, do you have a 4400? If so, then the $5.00 thermistor should fix it. It fits behind the fuse panel. Remove the bolts holding the fuse panel and pull it out as far as you can. You will see a small square orange "chicklet" attached to the wiring in back. You need to cut out the old one and splice in the new one either by soldering it in or using small butt splice connectors. The part number is Lvu10323. ....

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John Deere 790 fuel shut-off solenoid failing

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randywilliam
Join Date: Apr 2011
Posts: 6 Blacksburg, VA
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2011-04-22          178121

JDGreen, Thanks very much for this information! I am going to try this. I appreciate everyone's comments and help. I'll let you know how it turns out. ....

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John Deere 790 fuel shut-off solenoid failing

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harvey
Join Date: Sep 2000
Posts: 1550 Moravia, NY
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2011-04-23          178130

Randy sorry about misunderstanding. I did the 4400 fix a year or 2 ago now and have had no isses since.

It is a pita to get to but easy enough to do.

....

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John Deere 790 fuel shut-off solenoid failing

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randywilliam
Join Date: Apr 2011
Posts: 6 Blacksburg, VA
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2011-04-23          178131

Harvey, So you replaced the $5 thermistor and it fixed the problem? Part # LVU10323? Thanks for your help. ....

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John Deere 790 fuel shut-off solenoid failing

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harvey
Join Date: Sep 2000
Posts: 1550 Moravia, NY
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2011-04-23          178133

Randy yes I replaced it. Much the same as you I had my doubts. But I figured $5 what to heck I try it.

Again I can't say enough good things about the guy with the info. It saved me a lot of money. There have been many other folks on here that have received advice that saved them money and headaches.

Anyways not one problem since. ....

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John Deere 790 fuel shut-off solenoid failing

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omurfe
Join Date: Jun 2011
Posts: 2 USA
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2011-06-13          178993

I have a 4600 and have replaced seelnoid fuel switch twice. Each time it is full of oil. I now hang it from the bench for three months and use the other. When it will not start switch the two and good to go for another 3 to 5 months ....

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