Power Equipment Forum banner
1 - 10 of 10 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
My Cummins P9500DF generator turns over with the electric starter but the engine will not catch and run. I'm forced to use the pull starter which works but is frustrating. I'm not the sharpest knife in the drawer mechanically but it appears that the battery that came with the unit is not powerful enough. If I add power with my jumper cables, the generator fires up immediately. I would add a larger battery but the battery space is very specific and won't accommodate a larger battery. I purchased a new battery but the problem exists. Cummins/Onan is a good name and it's hard to believe that they undersized the battery on this model. Appreciate your thoughts.
 

·
Registered
Joined
·
1,386 Posts
It could be one of two things... maybe even both.

Charge the battery using a suitable charger at least overnight. Also check that both battery terminals and the battery cable going to the starter and starter solenoid are tight.
 

·
Registered
Joined
·
132 Posts
I purchased a new battery but the problem exists.
Chances are your battery just needs a full charge to fix your starting issue, but you can also do a quick check.
Do you have or can you borrow a multi-meter? If yes, (with the engine not running), what 12 volt reading are you seeing? Now take another reading with it running, pull start if you must. I imagine the Cummins has the capability to keep the battery topped up.
The following 2 pics are simply examples (from an ATV) to help explain what I mean. This (6 year old) battery was replaced shortly aftwards due to it's low voltage at rest. I like to see at least a 12.6 or 7 minimum.

Vehicle Gauge Measuring instrument Motor vehicle Auto part

Gauge Measuring instrument Automotive tire Audio equipment Motor vehicle


If you end up shopping for another battery, I suggest looking for the largest CCA battery you can find within the physical dimensions of your battery tray/space.
 

·
Registered
Joined
·
1,386 Posts
Open terminal voltage is not the only way to measure SLA battery SoH. In fact, that can even be misleading.

Many bad batteries may show seemingly good voltage at rest, but once you pass serious current through them, the internal resistance starts to rear its ugly head and so the voltage drop would too great for the battery to say, crank the engine.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #7 ·
Thanks for your input. Sledman, the problem started early after purchase. Cummins said I had to take it to their SoCal service center (a 40 mile drive), then Covid hit and I just gave it a miss. This weekend, I charged the specified battery to 12.5V and the starter would turn strongly but the engine would not catch. I disconnected the specified battery and connected the cables to a 550CCA car battery I had. The generator fired up immediately.
My conclusion is that Cummins undersized the battery and I can live with the larger battery sitting next to the gen. My question is, If the specified battery is strong enough to turn the starter, why doesn't the engine catch?

When I purchased the generator in 2019, it was a new introduction. I wonder if Cummins has changed the battery. I don't think the generator has the ability to charge the battery. A closer look at the instructions indicated that I should have received a plug in to connect to the battery terminals from a "Battery Charging" port. I did not receive that plug in.

I'm a big Harbor Freight fan but shied away from their generators. I'm thinking I should have purchased from a store that has locations everywhere.
 

·
Registered
Joined
·
132 Posts
charged the specified battery to 12.5V and the starter would turn strongly but the engine would not catch
Are you saying it was 12.5 after fully charging? If yes, that's too low/weak IMO. When under the starting load the voltage may well be falling into the low 11's (or lower) taking away from the needed power the ignition system also requires for a start.
Have you ever changed or looked at the spark plug? Is there a Torch branded plug in it? If yes, that can be an issue in itself, remove it and install a name brand plug such as a NGK or Champion. The Torch's are known for failure, I myself have zero confidence in them.
 

·
Registered
Joined
·
132 Posts
I don't think the generator has the ability to charge the battery.
Being a modern electric start unit I believe it should. I just did an owners manual search, is this your Cummins gen?

At the bottom of page 12 I snipped an item from it ---

Rectangle Organism Font Parallel Water


I see this model as a Dual Fuel, if this is your gen are you using gasoline or propane? I have no experience dealing with propane running engines, but the reason I ask is if you're using propane (from what I'm understanding) your spark plug replacement should be an NGK iridium.
I see on the bottom of page 28 it shows spark plug specifics---

Font Rectangle Handwriting Electric blue Writing


If all you can locate is a BPR7ES plug, (and just running gasoline), it will also work fine IME. Regardless, I suggest removing the Torch.
I should have received a plug in to connect to the battery terminals from a "Battery Charging" port
According to the above manual yes you should have. Still have the box it came in? The charger may be stuffed into a pocket of the shipping styrofoam.
 

·
Registered
Joined
·
485 Posts
I had a similar trouble with mine where everytime I turned the key it would turn over for half of a second then stop.. But the engine would start after the 3rd-4th turn of the key.. A new battery sorted that problem.
 
1 - 10 of 10 Posts
Top