I have 2 Cummins generators one has a 6LTA8.9-G2 engine and the other has a 4BT3.9-G2 engine with Stamford alternators. The Cummins engines are made in China and we are trying to parallel with the mains supply. The problem with them both is the engine speed is unstable which is not allowing it to synchronise properly. It surges and hunts when it goes to parallel with mains. We have fitted a good quality GAC governor and have adjusted the stability and speed carefully to try and stabilze it without any luck. Has anyone had a similar problem before and do you think it could be an injector pump problem across the board for all Chinese built Cummins engines? Any suggestions or fixes? Thanks

SOURCE: Coleman generator OHV3000

The carburetor is probably clogged up. Mix a bottle of carburetor cleaner with the gas to see if that would help. Also check/replace the fuel filter.

SOURCE: ENGINE OVER SPEEDS WHILE RUNNING

This is almost surely a problem with the governor, check it like this.
Have someone with a finger on the kill switch.
Watch the governor arm while starting the engine, if it does not move almost immediately after starting the engine it is broken.
This is not a simple repair as it involves taking the crankcase apart, you'll have to contact robin/subaru to get a parts list in order to get the right governor spool and weights.
For an experienced technician this is about a 2 hour repair task.

Hope this helped,
Carl

SOURCE: Porter Cable 5500w generator (10hp BS) will not regulate speed.

While attending college I worked at a tool rental center and learned a great deal about matching generators to customer requirements and troubleshooting customer owned units. There are simple tests that you can perform, however, first some info on what to expect from a generator. Most generators are overrated and under powered. You should only expect to get about 60 - 75% of rating. Example, a commercial honda 5000w generator has an 11hp motor that can only produce about 9.5 hp at 3600 rpm. If a customer needed 5000w of power, we would rent them an 8000w generator because as the generator is loaded to max the voltage will drop. You generator will probably only provide steady voltage ex. 115v at 60 cycles to about 3500w then voltage will begin to drop. New generators have automatic voltage regulator that varies the power to the armature increasing/decreasing the power of the magnet. These voltage regulators suffer a high failure rate and are expensive. If your generator is not giving you 3500 watt at 115v 60 cycles your engine may have a few problems and your power generator end may need tweaking. (I would not expect to achieve 5500w at 115v with briggs 10hp) .
The governor is about 2 inches in diameter and turns off the cam gear inside the engine. It is flyball type with two or three small arms that react to rpm. The faster the engine turns, more force is applied to the governor arm to reduce engine speed. Easy to test, with engine running use finger pressure against the arm to increase speed and you should feel a greater resistance as the engine speed increases. Another simple test, remove air filter to expose butterfly inside the carb. Move the governor arm and check that the butterfly opens fully. If it does not open fully linkage and governor is not set correctly. Next, start engine and load generator up to max and check that butterfly opens to full as the load increases. When the butterfly opens all the way under load the engine is at max. Add up the wattage of all the tools/appliances you used to load the engine to get an idea of max load . Lets assume that the shop adjusted the governor properly, if the governor was not working the engine would over rev. and damage would occur. As you were told the governor spring controls speed and can be adjusted somewhat by bending tab or adjustment screw. But a review of your generator manual or that series of briggs engine will show that there are several governor springs available and different placement holes on the governor arm to attach the spring that will change the power curve. Pulling on the spring can only do so much, however changing the spring to different gauge /turns/material or differnet location on the governor arm will cause the engine to perform differently. These springs are sold thru briggs dealers by part number for your engine. This would be considered tweaking to get a different power curve.
Now for the generator. Some generators have a capacitor incorporated in the windings. This capacitor must measure within 95% of rating. Remove from circuit for testing. Finally look very carefully at the commutator rings for any evidence of brush bounce. If the brushes do not perfectly seat you will lose power. If your generator is brushless you can only hope that the diodes are within spec. because it is too difficult to test them. They also must be removed to test. Finally if your generator has an automatic voltage regulator the only test would be to replace with a known good part. At the rental center we stocked spare parts so that we could quickly find fault. There is soo much to learn and the life too short. I hope this helps good luck, please email your questions.

SOURCE: Coleman Powermate 3000 surging

Check your air filter to make sure it is clean, especially if the gen. has been run in dirty, dusty conditions. Make sure the gas tank vent is not clogged.

Also, pour some combustion cleaner into the carb. through the air intake to clean the carb. It sounds like it is starving for gas.

Hope this helps.
Rob

SOURCE: Engine over heats on Lister Petter AD1 generator

If it's over revving then more than likely the problem is in the governor. The governor is under the fuel pump and thats what regulates the engine speed.

Testimonial: "Thanks alot for your help."