Voltage Drop / No Start

[Sgots]

New to the Forum and there is some great information here, I hope you might help me out.
On a 3710 w 750hrs. Ran fine till yesterday, worked her for a couple hours then she won't start. PTO and clutch switches are in the right spot. May Batt is solid and showing 12.8v. When I turn the key, my glow pug light cycles for part of a second (unusually brief) then the eng & oil press lights dim significantly. I can hear a (solenoid/relay?) right behind the key, buzz/click for a few seconds...then nothing. Still have the dim lights on the dash.
Tried to jump the starter off the battery but with the key "ON" I'm only getting 7v off my battery, while with the key off, I have 12.8v.

Am I looking at a new ignition switch or is there a relay between the key and the starter relay? And where are those electrons going? Even with the Key "ON" for several min, I'd expect a 6.5v drop to drain my battery more.

Appreciate any help you might lend.

 

[North Idaho Wolfman]

Take the battery out and take it to an automotive store and have them load test it. It sounds like you have a dead cell?
But then again even with a bad cell it should do something.
Manually jump the starter right at the solenoid with the key off it should crank if it doesn't it could be a cooked starter.

 

[kubotasam]

Check for dirty or corroded battery cables ends and clamps. Also clean battery posts.

 

[Sgots]

Thanks Wolfman & Kubotasam - Terminals are pristine. I don't think a bad cell would account for a 6 volt drop when the key is "On" but return to normal volts when the key is off. Tried a jump start off my truck the only difference was the "Buzzing/clicking" noise behind the dash/key was a LOT more active.

 

[seanbarr]

Wolfman's advice should be the first step. Just because you can read 12.8 doesn't mean there's enough juice in the battery. What you could be reading is a "surface" charge. It's normal for vehicles to read a drastic drop to as low as 8 volts while the engine is cranking (gas). Take the battery in for testing to narrow down the problem. If its the battery, get it replaced AND check your charging system soon if the battery's not that old. If its good, you now need to look elsewhere, starting with the starter circuit.

Also fyi, an unsecured battery can have a shorter life span with excessive vibration which isn't good for it.

When jump-starting, keep in mind that diesels are generally harder to start than gas due to the compression required. With any type of jump-starting procedures, it's always recommended to allow the "dead" battery be charged for a minimum of 5 minutes especially if the cables aren't thick enough. Tow truck operators have thick welding type cables which allow much higher amp flows for quicker starting. They can practically start vehicles without the battery for that reason.

Hope it helps.

 

[ETRon]

Either you're not charging or the battery is toast. Try charging the battery via battery charger and see if it holds the charge. If so you have a charging problem, if not then it's the battery.

 

[Sgots]

Been using the rig 2-3 times a week since Spring, and never had a starting problem. Good volts on the Battery and she would not take a jump. So.... confidence in the Battery was high. I had already found and priced a John Deere AM107421 relay kit but I didn't ask for your help just to ignore it. Took the battery to the parts store, she failed a load test New Battery bought and installed and my rig is up and running!

My thanks to you all for your help and insight.