1987 Hitachi UH123 Excavator EM100 Hino engine Batteries tested OK (these are the huge D4 batteries approx.2 yrs old) Starter has been bench tested OK All Relays + Regulators have been bench tested OK Symptoms- Engine will not crank everytime key is turned. Mostly will not crank when engine is hot Jumping the starter with screwdriver works most of the time but eventually I get nothing but a click or trying to crank or nothing and then the batteries removed , hooked to the charger reading about 20 (on charger needle) and after a long slow charge never gets below 10 (on charger needle) Then when reinstalled - usually starts with key for the time being. With cab interior light on, ignition key is turned to crank position,cab light does NOT dim while attempting to crank engine. This machine has that odd type key that resembles an old school soda machine key. I'd replace the ignition but having a heck of a time tracking one down. Any opinions ??
I had battery cables get corroded inside the insulation and loose conductivity on a truck once. You wouldn't know it by looking at them. Sometimes the truck would start, some times it wouldn't. If you can replicate your problem try taking a good jumper cable (meaning something better than those cheap cables that are hardly bigger than an extension cord) and going from the negative post on the battery to the frame of the machine and see if your problem is solved. If that doesn't work try using the jumper cable and go from the positive side of the batteries to where ever the other end of the positive cable on the machine goes. Might be the starter or possibly a lock out switch. If it goes to a lock out switch also try jumping the lock out switch and jumping from the lock out switch to the starter. What you are essentially doing is bypassing the machines cables with the jumper cable to see if you can find your problem. Good luck.
I had the corroded battery cable issue on a diesel pickup recently . Good Point. Using the jumper cables on both pos and neg sides of the electrical system is a great idea also. I'll post an update when I get a chance to try these fix's . Thanks :usa
I have a Hitachi 143 and had a no start problem last year. I finally narrowed it down to a pair of relays behind the panel under the throttle control. I tapped the relays while turning the key and it started. I took relay apart and cleaned and bent the contacts so they closed tighter and it worked. I called a Deere dealer to order a new one, well good luck getting one, it seems the only way is to find one that is old stock cause not made anymore. The Hitachi 143 is the same machine as the Deere 792. Only difference is that I also have a Hino EP100. Nick
There is a battery relay behind the battery box that also went bad on me some time ago that caused a no start. Check it out. I have a service manuel and parts book with electrical info if you need info. I'm sure the machines are similar except for size. I have an original 123 sales pamphlet, the 123 and 143 look identicle.
The relays below the throttle handle are easy to access. Remove plate under throttle. 10mm I think, push seat back and you can see them. They look like horn relays, try swapping them around. Nick