Cummins Onan LP 25 won't start...
Hi all. I'd like to get some help with a 7-year-old Cummins Onan LP generator that won't start. I've tried to do as much as I can before potentially wasting your time on a problem that I overlooked. The particulars of what I have done and what I have observed/measured follow...
2016 Mercedes Sprinter Van Conversion
Cummins Onan LP 2500 Generator
2.5HGJBB-1121A (spec A)
Subaru X21 7HP Engine
This belongs to my friend, and he hasn't used the generator in quite a while and did not "exercise" it during that couple-year period. Now it won't start -- doesn't even try -- but cranks with no indication of any kind of problem. The blink code simply reports error code #4 which says that I've run the starter for 15-20 seconds with no result.
- The spark plug is clean and has a good blue/white spark. My assumption is that any of the sensor interlocks, such as the oil level sensor, would interrupt the electrical system and I wouldn't get a spark. But with a magneto -- which I think this has -- there may be no way of stopping the spark and they interrupt the fuel flow instead. I just don't know.
- The output of the two-stage regulator is 11" of water -- has been as high as 14" with no difference in the symptoms.
- The gas solenoid opens -- can hear the click -- and you can hear the sound of gas flowing when the start/stop switch is pushed to the Prime position.
- The LP Regulator works with no leaks -- pulled it, opened and examined, used a MityVac to put a small vacuum on the outlet and the diaphragm opened, allowing flow through the inlet. The LP regulator vent hose is clean and clear of obstructions.
- The throttle and choke assemblies move freely -- I've manually opened and closed each of them while cranking with no change.
- Air breather is new - have tried with it installed and without.
- There is no vacuum being pulled into the bottom of the mixer when the engine is cranking -- required for the LP regulator diaphragm to open the inlet valve.
- Cannot hear or feel the fuel solenoid open when the On/Off switch is in the Start position.
There are tons that I don't know about LP-fueled engines, but this seems to indicate that the problem is not directly related to the fuel system itself.
It acts like one or both valves are staying open, preventing the downstroke of the piston from pulling air in, and creating the necessary vacuum. Or that I'm getting air around the piston on the down stroke.
There was one other thing of note that appears to indicate a mechanical engine problem -- I forgot to put the oil cap back on before cranking it and it blew oil out with a pretty high pressure. The specs say that this engine uses "splash" lubrication so that may be normal but seemed pretty high pressure to me.
I'm gonna use an unlit propane torch to blow propane directly into the mixer while cranking and see what happens.
Also, I'm going to see if I can get a compression tester in -- there is practically no access to anything on this beast -- and prove/disprove this theory.
But in the meantime, I'm hoping some of you will read this and critique my troubleshooting and see if you agree with my "almost" conclusion regarding the engine itself being the failure point.
Thanks in advance,
Just a country boy from the cotton fields of Alabama trying to get by in the big city...
2016 Mercedes Sprinter Van Conversion
Cummins Onan LP 2500 Generator
2.5HGJBB-1121A (spec A)
Subaru X21 7HP Engine
This belongs to my friend, and he hasn't used the generator in quite a while and did not "exercise" it during that couple-year period. Now it won't start -- doesn't even try -- but cranks with no indication of any kind of problem. The blink code simply reports error code #4 which says that I've run the starter for 15-20 seconds with no result.
- The spark plug is clean and has a good blue/white spark. My assumption is that any of the sensor interlocks, such as the oil level sensor, would interrupt the electrical system and I wouldn't get a spark. But with a magneto -- which I think this has -- there may be no way of stopping the spark and they interrupt the fuel flow instead. I just don't know.
- The output of the two-stage regulator is 11" of water -- has been as high as 14" with no difference in the symptoms.
- The gas solenoid opens -- can hear the click -- and you can hear the sound of gas flowing when the start/stop switch is pushed to the Prime position.
- The LP Regulator works with no leaks -- pulled it, opened and examined, used a MityVac to put a small vacuum on the outlet and the diaphragm opened, allowing flow through the inlet. The LP regulator vent hose is clean and clear of obstructions.
- The throttle and choke assemblies move freely -- I've manually opened and closed each of them while cranking with no change.
- Air breather is new - have tried with it installed and without.
- There is no vacuum being pulled into the bottom of the mixer when the engine is cranking -- required for the LP regulator diaphragm to open the inlet valve.
- Cannot hear or feel the fuel solenoid open when the On/Off switch is in the Start position.
There are tons that I don't know about LP-fueled engines, but this seems to indicate that the problem is not directly related to the fuel system itself.
It acts like one or both valves are staying open, preventing the downstroke of the piston from pulling air in, and creating the necessary vacuum. Or that I'm getting air around the piston on the down stroke.
There was one other thing of note that appears to indicate a mechanical engine problem -- I forgot to put the oil cap back on before cranking it and it blew oil out with a pretty high pressure. The specs say that this engine uses "splash" lubrication so that may be normal but seemed pretty high pressure to me.
I'm gonna use an unlit propane torch to blow propane directly into the mixer while cranking and see what happens.
Also, I'm going to see if I can get a compression tester in -- there is practically no access to anything on this beast -- and prove/disprove this theory.
But in the meantime, I'm hoping some of you will read this and critique my troubleshooting and see if you agree with my "almost" conclusion regarding the engine itself being the failure point.
Thanks in advance,
Just a country boy from the cotton fields of Alabama trying to get by in the big city...
