Help Interpreting Wiring Diagram & Using Multimeter

[sriddle1]

Question comes to mind......Can there be a short within the Solenoid ? Output from X5 Harness side has 12V on both 658 Grn/Wht & 651 Wht/Blu (3 seconds). HOWEVER as soon I connect Solenoid to Jumpers that action negates the Pull in Coil (651 Wht/Blu), no voltage.

 

[sriddle1]

dieselcrawler, Questions if the Y2 Fuel Shutoff Solenoid has been proven GOOD. The 12V input is coming in over the harness for both the "Pull In Coil" (12V, 3 seconds) and "Hold In Coil" (constant 12V) simultaneously when ignition in RUN Position. If ground was an issue I would think (??) the Solenoid should Retract/Hold after I connect Solenoid to both 658 Grn/Wht & 651 Wht/Blu then use a separate jumper directly to battery negative terminal for BLK termination. Still didn't work in that lash-up, as explained above the "Pull in Coil" voltage coming in on the Harness is not found once connected to the solenoid.

 

[Egon]

Is there one of these yellow things behind the panel on your tractor. If there is change it. Five dollar item.

[video]https://www.google.ca/search?q=thermistor+jd&client=safari&hl=en-ca&prmd=ivsn&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjZmqy-8OfPAhUZ3YMKHWpKBGgQ_AUIBygB&biw=1024&bih=681#imgdii=fqlPEE2DlwnqMM%3A%3BnpGvRhOHwaPi8M% 3A%3BnpGvRhOHwaPi8M%3A&imgrc=npGvRhOHwaPi8M%3A[/video]

[video]http://www.greenpartstore.com/John-Deere-Thermistor--LVU10323_p_23272.html[/video]

 

[sriddle1]

Is there one of these yellow things behind the panel on your tractor. If there is change it.

Egon, Thanks for the post..... Read about the John Deere Thermistor - PN: LVU10323 last month when initially investigating non-starting symptoms. Performing a "Where Used" Search for that Part Number within the John Deere Parts Catalog identifies usage in Tractor Models: 4200, 4300, 4400, 4500, 4600, 4700 and not in my Model 790 CUT.

 

[Zebrafive]

Question comes to mind......Can there be a short within the Solenoid ? Output from X5 Harness side has 12V on both 658 Grn/Wht & 651 Wht/Blu (3 seconds). HOWEVER as soon I connect Solenoid to Jumpers that action negates the Pull in Coil (651 Wht/Blu), no voltage.

If there was a short you would blow a fuse, or melt a wire if no fuse in the circuit. I doubt there is a short.

 

[Zebrafive]

I think you have narrowed it down to either the K2 FR (Fuel Relay), or the TDM (Time Delay Module).

It sounds like the K2 Fuel Relay is not maintaining voltage to the white/blue wire. This could be a bad K2 FR or TDM
The Green/White wire comes from the Time Delay module and goes to BOTH the K2 Fuel relay's coil AND to the Fuel Shut Off Solenoid. The TDM also provides the ground to the K2 FR coil.

You could swap in a new relay for K2 FR, or swap K1 Start Relay from the tractor.
You could check the wiring to/from K2 relay.
K2 relay will have 4 wires:
1) Lt Green 658
2)White/Black 451
3)Green/White 655
4)White/Blue 650

1) Lt Green 658, is the relay coil ground. The TDM grounds this wire to activate the relay.
2) White/Black 451, is 12volts from the ignition switch (KEY Switch) it will have 12 volts, Key in RUN. Use your meter and check for 12 volts
3) Green/White 655 is same as Green/White 658 to Shut Off Solenoid. (Number changes because of a splice) Use your meter to check for Continuity (Meter on OHMS) White/Green at X5 connector to terminal 3 White/Green wire at K2 FR
4) White/Blue 650 is same wire as White/Blue 651 to Shut Off Solenoid. Check it for continuity too.

The way to check the above two continuity checks is with the relay out and meter leads to the relay connector at the wire color indicated.

If the relay is OK, you have voltage to 2, continuity of 3 & 4 is OK, that only leaves the Lt Green wire. Either it is broken between the TDM and K2 FR or the TDM is NOT grounding it. You can check continuity from the 1 Lt Green wire at K2 FR and the Lt Green wire at X4 which is the connector to the TDM. If it has continuity, then the wire is not broken.

One last thing you could try (after trying all of above) is bypassing the TDM ground for K2 FR (1 Lt Green wire). To do this you need to attach a wire to the Lt green wire either at the K2 FR or X4 connector (try inserting a stripped wire into the back side of the connector) and ground the other end of this wire. If bypassing the ground function of the TDM fixes the problem replace it.

 

[sriddle1]

Zebrafive,

I was getting a bit worried :worried: so I went ahead and ordered the 790 CUT Shop Technical Manual from JD this morning on CD, was surprised so cheap, only $52.00 to include shipping.

I really want to thank you :thumbsup: for your input to this thread, your initial step-by-step (spoon feeding me) voltage checks that has gotten me to the point of testing the Solenoid using dieselcrawler's jumpers. While performing those initial checks you recommended I want to mention an anomaly, my multimeter read approx 10 volts coming off the battery terminals after fully trickle charged and same 10 volt outputs in each step, my multimeter scale is pretty small so I was off a couple of volts.

Per dieselcrawler, when I simultaneously applied the direct voltage from the battery to both the solenoids RED, WHT and BLK grounded directly to the battery it appears the 10 volts was enough to retracted the plunger. I know I'm repeating myself but it appears you were able to wade thru my feedback and now the NEXT SET of very detailed checks you are providing :thumbsup: that I will perform tomorrow morning. THANK YOU AGAIN, will report back the results..............

 

[Zebrafive]

The tech manual on CD should be helpful. I bought one for x485 and had a print shop print it all and "drill" the pages for 3 ring binder. They said it had too many pages (almost 600) to spiral bind, which they also can do.

 

[sriddle1]

I think you have narrowed it down to either the K2 FR (Fuel Relay), or the TDM (Time Delay Module). You could swap in a new relay for K2 FR, or swap K1 Start Relay from the tractor.

Good Morning Z5, Reviewing what you've written before heading out to the garage. Also, at the same time have my posted wiring diagram in-hand and now looking at the John Deer Parts Catalog to identify/locate the K2 Fuel Relay, K1 Start Relay and A1 Time Delay Control Module. I'm in the Parts Catalog Section 59 - Battery and Wiring Harness (790000-1) since my tractor is Serial Number LV0790G790056. I found the A1 Time Delay Control Module = M803344, the K1 Start Relay = M805280 but having a bit of trouble finding the K2 Fuel Relay, the only other relay I'm seeing is for the Flasher :reading:

 

[sriddle1]

Progress for today - CRITTER STUFF !!!! Removed plastic shroud below Instrument Panel (PIC 7105) and found that cavity filled with Typical Rat Poison Green Granules, Straw, Bunches of chewed material looking like that ground insulation...... Anyway, vacuumed it out (PIC 7113) and that Oklahoma Clay where I purchased the 790 still abound but I can plainly see the A1 Time Delay Control Module to the UPPER right. No chew marks on wire or connectors at first glance (hope that thought remains after tomorrow), looks like the critter had a smorgasbord of things to munch-on instead. Tomorrow I'll have to sort out (tracing wire colors) to locate the K2 Fuel Relay, K1 Start Relay. I suspect they're above the opening, but then again maybe not..........:reading: