20kw Will not Start

Generac, Guardian, Honeywell, Siemens, Centurion, Watchdog, Bryant, & Carrier Air Cooled Home Standby generator troubleshooting and repair questions
Post Reply
jimss
New Member
New Member
Posts: 4
Joined: Wed Mar 18, 2020 3:43 pm

I recently became the proud owner of a Generac 20kw backup generator, model 0058871, s/n 7067597 which, until recently, seemed to exercise properly. It looks like the last maintenance was in 2018, as far as I can tell, with about 188 hours on the meter. At that time, the complaint was for overcrank, but did not have that issue when the maintenance was done. Lately, it has given an RPM sense loss, so I figured the battery was the most likely culprit (it was at least 4 years old). Changed the battery, cleaned the battery connections, and cleaned/checked the starter ground connection . No joy. It will crank, but to me it seems sluggish. Starting in manual, it will go through the first 15sec try, but after the 6 sec rest period, will not turn for the second try. Voltage at the starter seems to be about 10 volts when cranking, 12.6 volts when idle. A resistance check of the cable comes up at about .5 ohm. Any insights you may have would be appreciated.
Chris
Site Admin
Site Admin
Posts: 1529
Joined: Sat Aug 04, 2018 8:46 pm
Location: Clawson, MI
Contact:

That sounds like possibly a bad cable connection or a bad ground behind the engine. Reach back behind the engine and grab ahold of the black ground cable (you can't see it) and see if it's loose.
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
Looking for Generac parts? Gentek Power offers the full line of Generac replacement parts! Shop Gentek Power Generac Parts
A list of my favorite Generator & Electrical Tools! https://www.amazon.com/shop/gentek_power
jimss
New Member
New Member
Posts: 4
Joined: Wed Mar 18, 2020 3:43 pm

I thought about that. After blindly grabbing what appeared to be the ground, it loos to be tight. As a workaround, I jumped the battery negative post to the starter motor ground screw and tried it again. Same results, cranking at about the same speed as before. It also only went through one crank cycle...the second attempt after the rest period only produced a click with no turning. Maybe the solenoid isn't happy? I'm kinda puzzled by the lack of a start on the first cycle. It has spark (plugs are new and gapped to .030). Gas pressure out of the meter at the inlet is about 5.7" H2O. I also checked the stepper, and got 10-11 ohms between all leads and the red lead. Red to ground is open. The only thing I haven't looked at is the valve clearance....That was supposedly done 2 years ago. I'm beginning to think its a fuel problem...natural gas is usually pretty easy to ignite if the mixture is right....
Chris
Site Admin
Site Admin
Posts: 1529
Joined: Sat Aug 04, 2018 8:46 pm
Location: Clawson, MI
Contact:

Are you able to capture a video and upload to YouTube then post the link here? I'd like to hear what it's doing.
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
Looking for Generac parts? Gentek Power offers the full line of Generac replacement parts! Shop Gentek Power Generac Parts
A list of my favorite Generator & Electrical Tools! https://www.amazon.com/shop/gentek_power
jimss
New Member
New Member
Posts: 4
Joined: Wed Mar 18, 2020 3:43 pm

Well, I can try. I’ a low tech guy in a high tech world, so it’s likely to get ugly.
jimss
New Member
New Member
Posts: 4
Joined: Wed Mar 18, 2020 3:43 pm

No joy on posting a video...I couldn't get the machine to repeat the earlier behavior. It degenerated to a click and an attempt to turn on starting...but no rotation. Further diagnosis (and a lot of cable jumping) pointed to a bad battery ground cable. That was the easy part. Disconnecting from the termination on the engine block was not easy...or possible. I could loosen the stop nut on top, but had no access to restrain the bolt from underneath while removing the nut. The last resort was to cut the cable at the engine, and run a new, longer ground , this time terminating on the front side of the block near the oil filter (where access actually exists). A little Noalox at the connection should help the aluminum behave. After that, it cranks and starts like a champ. There is a special place in hell for the guy(s) at Generac who designed the enclosure for "easy access".
Chris
Site Admin
Site Admin
Posts: 1529
Joined: Sat Aug 04, 2018 8:46 pm
Location: Clawson, MI
Contact:

Yea, the rear ground is not something 'fun' to replace... :sad: I'm glad to hear that you were able to come up with something though, and that it's working!
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
Looking for Generac parts? Gentek Power offers the full line of Generac replacement parts! Shop Gentek Power Generac Parts
A list of my favorite Generator & Electrical Tools! https://www.amazon.com/shop/gentek_power
Post Reply