M-920 in dash starter solenoid

[Karl kostman]

Hello Folks I have a question for you concerning my M-920! The truck is your normal 1980 M-920 tractor all original and has 609 miles since complete rebuilt, the question I have is I have been running into some road blocks it seems to get it started, I did have it running when I got it then it sat for awhile and I had to charge the batteries on it. OK with that said I have 3 out of the 4 batteries charged to around 12.5 volts and one battery at 11.08 volts, in my usual state of blissful ignorance this would sure seem like enough to start the truck, again remember the blissful part! What I got this morning when I tried to start it the solenoid in the dash just seemed to bounce, this is the solenoid that connects the 24 volt circuit to the starter when you push the start button, every time it bounced and made contact the engine turned over a tiny bit but the solenoid would NOT hold the connection hence my term of BOUNCE! Could it be that having 1 battery only at 11.08 volts is causing this or do you feel that the in dash solenoid that gives the starter 24 volts is bad and needs replacing? I know some things can be very voltage sensitive but wow if less than 1 volt would cause this that is REALLY sensitive! Any thoughts would sure be appreciated!
Thanks much
Karl

 

[Baradium]

Either low voltage or bad ground. It's possible the solenoid is weak, but I'd guess the voltage or ground part. What's happening is as soon as the starter engages the voltage drops too low to keep the system energized so it's disengaging.

Will the 11.08V battery not take any charge at all or did you not get to it? It might not be just 1.4 volts when under load.

 

[R Racing]

Ok 2 things here the battery with the low voltage has a shorted cell. Replace it ASAP. Second check your netural safety switch in the shifter. Also a third posibility could be a bad ignition switch. But 1st I'd get rid of that battery. I had 1 in my m920 that costed me tons of grief! !!!!

 

[Karl kostman]

Thanks for the great suggestions guys I have the low voltage battery isolated now and its charging by itself we will see if that gets to 12 volts or higher after charging if not then it will be replaced, in the mean time I will start going over possible ground problems before replacing that solenoid in the dash, Thanks guys for giving me some good direction in this issue I will let you know how it goes as things progress!
Thanks again
Karl

 

[Artisan]

I use just 2 Sears, I think they are a B-19 marine battery in
my M916. Spins FAST, starts right up...
(Same engine)

 

[Artisan]

I mention 2 batteries so you could use just two and
see if it starts differently.

P/N SAZ 4201BR RELAY-SOLDENOID,ENGI

 

[Csm Davis]

That solenoid in these trucks tends to have problems with under voltage, known problem in service and not fixed. If you want you can use a small piece of metal to jump across that solenoid and crank the truck many times when the voltage is not enough to do so with the starter switch alone. But I would say change out the batteries as soon as possible you really need all batteries in the system to be at 13 volts or more to avoid problems.

 

[lindsey97]

When multiple batteries are connected together in a series, they become "one battery". In your situation, with one battery at 11.08 volts, it will try to equalize the other 3, thus bringing the overall voltage down.

Voltage is a measure of stored energy (amps). When a battery only has 11.08volts , it's internal resistance is so high that it can no longer take or hold a charge, thus no amps and the low voltage.

It would be best to replace all 4 batteries at the same time, although it isn't always easy on the wallet. Check your ground cable' s ends where they bolt to the frame, and make sure all of your cables are good, and have no corrosion inside them. I have a Cat D4c bulldozer, and after replacing the starter, batteries, amp gauge, and everything else, I removed both battery cables and cut the insulation off of them. They both had internal corrosion that wasn't visible from the outside. I had new custom cables made, installed them and the Cat started better than it ever had in the 12 years that I have owned it.

Also consider a 110 volt coolant heater for your truck. It will make a huge difference inn cold starts in your environment.