Hi all, I am new here.I have an Onan HGJAB-1038C Spec C generator that is surging while under a load from the A/C. It will do this for a minute or two then die.I just replaced the carb and camping world said the choke wasn't adjusted properly. I don't think they put it under a load though because it was cold out.It runs great not under a load and will start right back up after it dies as long as there is no load on it. I put a temporary fuel line into a fuel jug to see if I had problems with fuel flow from the tank. I checked other things as well and from what I can tell it is not a fuel delivery problem. I also made sure the oil is right up by the full mark.Not sure where to go from here other than back to camping world, but that is expensive sometimes.

Pump? That would be my guess. Putting the line in the gas can next to it still used the same pump. All that rules out is crack or air penetration into the fuel line from the tank.

It sounds lean and it's showing most when the ac is on. You need to further prove that the fuel system is ok. There shouldn't be any restriction in the carb because it's new so you need to check fuel pressure and volume. What type of fuel pump does it have? So you connected another small fuel tank to the fuel pump to eliminate the lines and tank.The only time the choke is used is at cold start up. When the engine has warmed and if the choke pull off system is working the choke will stay open. If manually slightly closing the choke seemed to help the engine run better it would seem that you have a lean issue. You have to have fuel volume, fuel pressure, proper float level, clean carb orifices and no vacuum leaks and not sucking air on the supply side.You have eliminated 3 of them.

OK, thanks for the replies. I will check it out further as soon as I can and report back here on my findings. It could be a couple days though.The pump seems to be working OK. Sounds like it always has. I did test it a while back and it pumped fuel pretty good. I don't have a way to pressure test it though. It is the standard Onan pump that goes on the generator. I will get the part number off of it. I saw it earlier today, but I can't remember the number.If it is running lean, how do I adjust that? It has the altitude adjustment on it and it is almost down to 0. I am only about 800 feet above sea level.

So it's a mechanical pump not an electric? If it had a high speed adjustment it would most likely be on the top center of the carb. If you were looking down on the carb the adj needle and the bowl nut would line up. Another place some carbs have a high speed adj is on the carb bowl nut. Most newer engines have fixed jet and are not adjustable.Have you checked the governor settings? Are any throttle linkages binding? Some throttle linkages have a long thin spring on the link itself. Each end of this spring would connect to throttle arm or gov linkage. They are used to take slop out of the linkage to prevent surging and erratic throttle shaft movement.

Does it present a code from the start switch? (light blink sequence).Mine properly reported under-voltage, and shutdown.. it could not tell me the motor side of the generator pulley rubber had failed..

Onan 5.5HGJAB-1038C | Good Sam Community

13 Replies

carterw65
Explorer
May 10, 2015
OK, thanks for the replies. I will check it out further as soon as I can and report back here on my findings. It could be a couple days though.

The pump seems to be working OK. Sounds like it always has. I did test it a while back and it pumped fuel pretty good. I don't have a way to pressure test it though. It is the standard Onan pump that goes on the generator. I will get the part number off of it. I saw it earlier today, but I can't remember the number.

If it is running lean, how do I adjust that? It has the altitude adjustment on it and it is almost down to 0. I am only about 800 feet above sea level.
azrving
Explorer
May 10, 2015
It sounds lean and it's showing most when the ac is on. You need to further prove that the fuel system is ok. There shouldn't be any restriction in the carb because it's new so you need to check fuel pressure and volume.

What type of fuel pump does it have? So you connected another small fuel tank to the fuel pump to eliminate the lines and tank.

The only time the choke is used is at cold start up. When the engine has warmed and if the choke pull off system is working the choke will stay open. If manually slightly closing the choke seemed to help the engine run better it would seem that you have a lean issue.

You have to have fuel volume, fuel pressure, proper float level, clean carb orifices and no vacuum leaks and not sucking air on the supply side.

You have eliminated 3 of them.
Pirate1
Explorer
May 09, 2015
Pump? That would be my guess. Putting the line in the gas can next to it still used the same pump. All that rules out is crack or air penetration into the fuel line from the tank.

Forum Discussion

Onan 5.5HGJAB-1038C

13 Replies

About Technical Issues

Related Content

Onan Problem

Onan Generator

Onan Running Problems

Dead Onan Generator

onan 5500