790 Sporadic Starting

[sriddle1]

Last couple of weeks noticed this occurring more and more. At one point I reversed the starting key (25 seconds) to get the glow plug going, still didn't start. I check the Fuel Filter, opened the drain and full of fuel. Purchased diesel within the past month, Shell Brand. Changed the Seat Safety Switch last week thinking that was possibly the issue, battery all charged...... For you seasoned mechanics (which I am not) any suggestions or steps to isolate the problem further. THANKS

 

[RobS]

Does it crank and not start, or not crank?

 

[sriddle1]

Does it crank and not start, or not crank?

Rob S, Thanks for the Response...........Thought of that on my drive back home after posting, should have added that data point. YES, it cranks strong in all occasions, sometimes it starts and sometimes not. Thought with winter coming up, removing FEL & installing front-mount snowblower, not a good time to figure this out.....

Just read this thread, I'll look at these things tomorrow.........

http://www.tractorbynet.com/forums/john-deere-owning-operating/206564-jd-790-cranking-but-not.html

 

[dieselcrawler]

Fuel stop solinoid could be going bad, or, as I've found on a similar solinoid on equipment at work, the wiring going to it... I would be willing to bet that the solinoid will rest (unenergized state) in the 'kill' position. It will likely have a dual coil, one to draw it back to the 'run' position (higher amperage, short duty cycle), and another coil to hold it in that position (lower amperage, continuous duty).

If it cranks over good, check there. Simply removing the solinoid will let you test it, but be aware that if the tractor starts, you have no way to stop the motor until the solinoid is reinstalled, and it will likely leak oil from the opening.

 

[CCWKen]

Good argument for the manual cutoffs on the old Ford and Kenbota.
I never have any problem with those. Unless I forget to push it back in.

 

[sixdogs]

Does the 790 have a cold start package? If so, my 5520 acted like that and had a bad sensor on the upper water inlet neck. I did a thread on it.

 

[sriddle1]

Does the 790 have a cold start package?

Sixdogs, My 790 is a 2009 Production Year so I'm unaware of a Cold Starting Package, it has an Ignition Switch position to supply voltage to the Glow Plug + I installed an Engine Block Heater while living in Minnesota @ -35 Winters..........FREEZING! I'm headed outside, cooler temps today mid 80s to go thru the items from the previous thread. I don't remember hearing the Fuel Solenoid "Chattering" as some mentioned, when it didn't start, Let the Troubleshooting Begin..........

 

[sixdogs]

These tractors are bulletproof so don't overthink this. Go with the easiest answers and work up from there. Maybe go see the dealer and ask what he thinks. That's how I found out about my cold start package. I had no idea.

 

[sriddle1]

Re: 790 Sporadic Starting - UPDATE

With notes from the Previous Thread's recommendations I commenced the search.... It started-up right off the bat and I heard the solenoid relay chirping before starting. First, the battery I replaced last year, double checked and terminals clean, connections tight and previously sprayed with the red battery terminal coating. Checked the ground going to the frame to the left of the battery, this tractor has been stored inside since it was new, no rust or corrosion but I still gave it a shot of CRC's Electrical 2-26 Lubricant. Next, Fuse Box... Pretty dirty in there, never have had it open, purchased this used in Oklahoma, still lots of red clay dust around the fuses. Gave it a good cleaning, noticed the "B" Solenoid 3 amp fuse blue'ish tab was almost bleached out clear, pulled it, replaced with spare, sprayed 2-26 over the fuse contacts after cleaning and closed-up. Turned tractor off, fired back-up, checked all the lights, etc. A-OK, and so we'll see in this on-going Easter egg hunt a.k.a. troubleshooting..

 

[sriddle1]

O-BOY, NOT STARTING THIS MORNING...........

Typical, when you need to get something done.....good thing I'm not in the middle of winter w/5 foot driftf, OK count to 5, relax, breathe deeply........ So, I thought changing the Seat Safety Switch the last go-around plus taking the steps I posted would do it, no such luck and the closest dealer is 40 miles away...... Battery all charged-up, Turns-over, I hear the chirping as I turn the key, in neutral, PTO disengaged, no mice eating wires..... and I'm beginning wonder (with no mechanical aptitude, guessing at this point....) could it be the fuel pump. QUESTION: Is there a simple way to tell if it is the FUEL PUMP?

 

[dieselcrawler]

The fuel pump is likely what you hear as you turn the key to the on/run position, before you get to the start position. I'm still betting on the stop solinoid, have you checked it yet?

 

[sriddle1]

The fuel pump is likely what you hear as you turn the key to the on/run position. I'm still betting on the stop solinoid, have you checked it yet?

dieselcrawler, Thanks for the response.......I'm Mechanically Inept putting it mildly but I do understand the Fuel Pump noise so I believe you're correct, unless it can make noise and still not provide the necessary fuel. Am I correct in saying if it was still the Seat Safety Switch then it wouldn't turn-over or I wouldn't hear the Fuel Pump

In your last post along with your technical analysis you stated: "Simply removing the solenoid will let you test it, but be aware that if the tractor starts, you have no way to stop the motor until the solenoid is reinstalled, and it will likely leak oil from the opening." That prospect is pretty scary for someone like me who can snap a bolt or strip a screw in a matter of seconds. Any other less adventitious options to DIY check or perhaps I'll have to bite the bullet and have the JD Dealer in MA pick-up.

 

[Egon]

When you turn the key there is usually a "clack" noise. This is the solenoid activating the injection pump. No clack the injection pump is not engaged. There really isn't a fuel shutoff.

In the electrical system there may be a link ??? that alters amps to the solinoid for opening and running. These have caused problems. They usually cost under ten dollars.

Might not hurt to inspect all the shutdown switches and make sure they work properly.

You should find lots of information on YouTube?

 

[dieselcrawler]

I took some pictures, I will upload and post asap. I am certain the kill solinoid is as I described in my earlier post, as also sure you won't hear it over the fuel pump.

 

[dieselcrawler]

Find the injection pump, right side, above the oil dip stick.



The stop solinoid is on the rear of the injection pump, will have 3 wires going into it. 2 bolts will hold it in place, likely with 10mm heads.



In the picture above, it is the cylinder shaped thing with the label on it, likely has 'Woodward' on it...

Remove it, test as described in my earlier post, just jog the motor, it should pull the pin in, and hold until the key is switched off. It will not pull in until the key hits the start position.

Good luck...

 

[sriddle1]

dieselcrawler, egon, THANKS for the response................

The PICs are great and really helps understand the location. Over the weekend I started doing some research on the Fuel Stop Solenoid and I believe you're right in your diagnosis. I can get an OEM Replacement on-line for around $110.00, far less than the hauling fees to/from the local JD. Would you recommend a certain Manufacturer. Wondering how hard that would be to Remove/Replace, just a couple of mounting bolts.... Watched a couple of YouTube videos of people pulling those and bench testing, looked simple......(as I get the shock) Read these solenoids have a tendency to stick/fail and my tractor is a 2005 so it doesn't owe me anything.

 

[Egon]

Make sure the solenoid is checked before purchasing a replacement. I now have two and both work!

 

[sriddle1]

Make sure the solenoid is checked before purchasing a replacement. I now have two and both work!

Egon, UNDERSTOOD......... I've been surfing the web on this issue, read the following: "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."

Everyone suggests pulling the solenoid, some say oil has a tendency to fill the plunger area and it can't retract..... I'm heading out with a 10mm, will report after pulling it......

 

[Egon]

Filling with oil may be a problem. On my tractor it's fine for quite a while and then no clack no start. Repeatedly pumping the primer lever and directing a heat gun at the solinoid has worked for me. So has a jumpstart as well as a slap on the cowl and encoraging words.

That part I mentioned is a Thermister.

 

[sriddle1]

FUEL SHUT OFF SELENOID

I'm heading out with a 10mm, will report after pulling it......

HOLD EVERYTHING ! Dieselcrawler, your PICs made it look so easy to access until I got outside and daaaaaaaaa, my JD419 FEL installed and the support arm goes right across that area...whaaaaat So, I'm going to punt for the moment and take a look tomorrow...... Still wondering about the Solenoid Timer Delay Module mentioned on Tractorpoint (link below). The person posting said he burned out a Fuel Stop Solenoid until he replaced that module.

Egon, Also read the "Thermister" you mentioned could also be a candidate. John Deere 790 fuel shut-off solenoid failing??? - John Deere Review - John Deere Tractors

ITS GET'N COMPLICATED !