Generac 4000exl has Fluctuating Voltage. But also Engine Rpms varying?

[Mastiffman]

 Hey guys, new to the forum, been on it for literally the last two days and I'm Diggin' it!

 Anyway, one fo the many things of duty.. I purchased a Generac 4k exl last fall for $100. it works but has fluctuating Voltage. one thing that is really evident is the Engines Rpms. They pulse. So I'm not sure if it's the Engine that is doing it, as I can get it to run a bit higher Rpms if I hold the the Throttle still but then it starts getting so hot that the muffler starts popping and spitting a flame out every few seconds... So not a good thing deal with. The Voltage Fluctuates between 103v and 113v...

 I know that the voltage regualtor could be the issue as well. I'm just windering where I should start to get thing running smoothly and outputing the proper Voltag, stably.

 The gentlemen that I purchased it from said that the 110 15amp plug supposedly "Just went bad", so he replaced it with a residential duplex box, outlet and Cover attached to the outside of the Unit!? Seemed a bit "redneck-ish" to me, but whatever I knew that I could get it and repair whatever was wrong with it.

 Thanks!

[Mary B]

Are you measuring this under a load? Toss a halogen shop light on it and see what it does.

[OperaHouse]

I have repaired a few generators for a friend in construction.  I am amazed at the number of defective brush holders for the rotor field I have found.  These have the plastic holder melted.  The carbon brush still has enough length and the spring is still good.  These brushes are easy to get at and remove by aking the back cover off.  If it is starting to stick you might be able to fix it for a while.  I found some on ebay for $18 + shipping.  An outrageous price considering they declare the life to be about 500 hours!

[hiker]

check your carb --might be running a little lean..
if it has overhead valves -check those as well..

[bob g]

i would about guarantee its the carb at issue
it likely is all gummed and corroded up inside

with the epa clamping down on everything buy my backside, the small engine oem's have had to setup their carbs to the gnats hair of too lean to start with, now after it gets a bit of old gas and some corrosion the thing will start to lean out, run irratically and finally not want to start or run at all.

the voltage fluctuation is related to changes in rpm.

take the carb off, and have it serviced if you don't know how. most any old dude that runs a lawnmower shop can assist you with this issue. failing that just buy a new carburator, often times they are available for less money than what you would have in a carb kit and labor to fix your old one.

with the pump gas today having alcohol in it, i see a lot of corroded crapped up carbs on small engine's in my shop, lots of them these days, it is by and large the most common problem i have come into my shop.  i think about a half dozen so far this season and  i am only a small garage that i do my own stuff in and not a business, i can only imagine if i am seeing so many the real shops are covered up with this problem.

good luck
bob g

[Mastiffman]

Okay. Excellent! I'll go ahead and check into all of this stuff and report back when I get some results...

 Questions:

-Wouldn't the Genny have a constant reading without a load if the Fuel saving Switch is turned off?
-If I'm getting a Voltage Reading Close to the proper rating would there still be a possibility of the VR being a Factor?
-Can I just use some Carb Cleaner to clean the carb once removed?
-If indeed the Carb is causing a lean running Engine, Would that cause the Muffler to be gummed up as well ultimately making it more possible for the Muffler to become a bit flamable? Or is the  Popping and Flame busrting out of it from the Lean Carb Setting?

 Great Community and Thanks a Lot!

[bob g]

i see as many carbs that are running lean as i do carbs that are running over rich due to gummed up needle/seat valves and floats that are cracked or have a hole worn into them.

if you got crap in the muffler, i would guess a rich condition, so check the air filter to see if it is clogged, see if the choke is opening properly, and check the engine oil to see if it is overfull and thinned out with gasoline. if it is overfull it will be sucked into the carb via the crankcase breather tube and run very rich.

carb cleaner is fine, if you take it all apart and are able to insure all those tiny passages/ports are clear. i use a piece of stranded copper wire to rod out the passages to insure they are  not only open but clear of corrosion. any reduction in size due to a layer of corrosion can effect fuel mix and make a lean run problem.

just giving you some idea's to look into, very hard to properly diagnose from afar.

bob g

[Mastiffman]

i see as many carbs that are running lean as i do carbs that are running over rich due to gummed up needle/seat valves and floats that are cracked or have a hole worn into them.

if you got crap in the muffler, i would guess a rich condition, so check the air filter to see if it is clogged, see if the choke is opening properly, and check the engine oil to see if it is overfull and thinned out with gasoline. if it is overfull it will be sucked into the carb via the crankcase breather tube and run very rich.

carb cleaner is fine, if you take it all apart and are able to insure all those tiny passages/ports are clear. i use a piece of stranded copper wire to rod out the passages to insure they are  not only open but clear of corrosion. any reduction in size due to a layer of corrosion can effect fuel mix and make a lean run problem.

just giving you some idea's to look into, very hard to properly diagnose from afar.

bob g

 bah!? That's what I was actually thinking of was being Rich... When Lean was Mentioned above... 


 Understandable... The Muffler looks pretty black. Woudl that be an indication of running rich?

[Mastiffman]

UPDATE:

 Went outside today and perform some inspections:

1. Pulled Carb off, Inspected Gaskets, Choke and Governer Funtioning. All checked out.
2. Pulled the Valve Cover off and everything looked normal. No Sludge and smooth oil. Air tube from Carb is a bit cracked but nothing major at this point. May replace in future due to age.
3. Found the Throttle adjustment Nut. (was hidden between the Starter coil and bottom of Fuel Tank. Tight but manageable.
4. Pulled the Spark Plug, Was COVERED in Carbon. I was told that it was replaced. Replaced the Spark Plug
5. I spected Plug Wire and it was fine.
5. Pulled Fuel Filter and replaced it.

 The Spark plug was fouling out. Must have been old. Replacement Plug and Fuel Filter with Throttle Adjustment and She Purs like a Kitten Now! Before Adjusting the Throttle I let her warm up a bit, Then Plugged in a light and Tested the Voltage and it was already mroe stable. But , it was only topping out at about 114.5v -115v. So I adjusted the throttl a bit and It's stable at about 120v.

 So just wanted to say Thank You fro all of the Suggestions! No Worries of Destroying my Refridgerator Motor now when the power goes. Since my wife and I moved in, in Jan. 2007 I've counted the power outtages and they are Currently at 45 outtages that range from a Cut off and then Back on to the Longest outtage which was just under 12 hours. So nothing Crazy except the frequency of them...

 So this guy is a happy Camper for now! 

[Bruce S]

Mastiffman;
Been reading this, glad to see it's running like it should without major stuff.
IF you can, try taking to muffler off and dumping as much soot out of it as possible.
The carbon in it could lead to clogging or too much back pressure.
Might let it run a bit (couple hours) to let it really clean out the cobwebs :-) and allow any other possible problems to show up now rather than later.
Happy Camping 
Bruce S

[thirteen]

I did not read all of the posts but maybe water  in the gas. There has been alot of that lately. If you see where they are unloading gas at a station go to the next one. They stir up the junk in the bottom of the tanks when pumping in 3-4 thousand gallons. Just an idea

[Frank S]

now that you have it running, and as someone suggested to let it run a couple of hours. since it is going to be running anyway you should load the generator with some kind of inductive resistance load like a couple of 2000w electric heaters start off with about 50% load for a few minutes then go to 75% and finally 100% for a few minutes monitor the heat of the generator I wouldn't  run 100% for more than 6 minutes out of 10 . by the end of an hour or 2 of this you will know how much you can depend on your unit in an emergency.
 For a further comment about something I did in the past look in the Hijack thread

[Mastiffman]

Mastiffman;
Been reading this, glad to see it's running like it should without major stuff.
IF you can, try taking to muffler off and dumping as much soot out of it as possible.
The carbon in it could lead to clogging or too much back pressure.
Might let it run a bit (couple hours) to let it really clean out the cobwebs :-) and allow any other possible problems to show up now rather than later.
Happy Camping 
Bruce S

 Thanks. Good idea about the Muffler. I'll do that today.

I did not read all of the posts but maybe water  in the gas. There has been alot of that lately. If you see where they are unloading gas at a station go to the next one. They stir up the junk in the bottom of the tanks when pumping in 3-4 thousand gallons. Just an idea

 I get Fuel from the Mobile Station at the Corner which hasn't received a fill in a fwe months, IIRC. So I shold be okay there. but this is why I chaged the Fuel Filter on the unit as well. it was looked kind of Dark. SO I figured that it couldn't hurt. but I will keep your suggestion under advisement when getting fuel and seeing a fill Tanker on the Site.

now that you have it running, and as someone suggested to let it run a couple of hours. since it is going to be running anyway you should load the generator with some kind of inductive resistance load like a couple of 2000w electric heaters start off with about 50% load for a few minutes then go to 75% and finally 100% for a few minutes monitor the heat of the generator I wouldn't  run 100% for more than 6 minutes out of 10 . by the end of an hour or 2 of this you will know how much you can depend on your unit in an emergency.
 For a further comment about something I did in the past look in the Hijack thread

 I don't have any heaters, but have a couple of AC Window Units not in use. So maybe those would Suffice? both are 115v aroiund 5 or so Amps I think. one is 6k BTU and the Other is almost a 10k. That is a good Idea as well. Although, I did have it running a mothn ago for about a good 7-8 hours and this was how I discovered the Issues. I noticed that all of my Water Pumps were Moving Noticeably Slower (first, by the Sound of the Rpms and then the lessoned surfice turbulence). So when I checked the voltage, it was around 103v-111v. But I set it to 120v Last night.

 One question that I was thinking about while trying to drift off to sleep was:
Is the Voltage is supposed to be set as Close to 120v without Going Over or is a 10ths over okay? Also, the Unit stated that it's a 120v 15amp but would it make a difference if I set it to run at 115v? Or would this lower the Amperage for the Duplex, and thus Not be a good idea?

[Mastiffman]

Okay, so earlier today I had a chance to go out and do some testing on this unit and preplug volts were between 120.1v and 120.9v.

 I used a 5k BTU AC unit that it rated @ 550w and a 9950 BTU AC unit rated @ 1110w.

 I plugged the 5k 550w AC unit in with the Volt meter plugged into the other duplexs outlet and when I turned on the AC unit the VOlts Drop to around 116v.

 Removed the 550w units plug from the outlet and When I tried the other 9950 BTU 1110w the volt started the same before turing it on, but then it drops to around 105v-109v...

 Mind you, that both units are 115v and the 550w is rated @4.9amps and the 1110w unit is rated @ 10.1amps.

 So my question is: Is it normal for the genny to drop in volts like that becasue of the motor Dealing with the Back EMF from the Draw on the Genny head? Or should I have had them Plugged in to the 120v @ 30amp outlet to do the load testing?

 Thanks!

[Mastiffman]

Okay, So I'm back at it again with this Genny.

 Worked for the most part when I needed it to. few weeks ago the unit just quit.

 Long story short, I had replaced the Spark Coil, LOS (low oil sensor) and Fuel tank. I went ahead and got everything that I need to get this unit back to its original working condition and purchased a Cart Handle (didn't have one), new 125v 15amp outlet that was gone and replaced with a duplex box, Valve cover Gasket (broke in half), breather intake tube, air filter, Another fuel filter and new fuel line as well as a new Battery and Float Charger. got her back together and in working order and here is the issue at hand.

 The idle control switch that helps conserve fuel is not working very well now. I'm not sure if I need to make an adjustment on the Governor lever or not... I can use my finger with fuel Conserver switch on and get the Governor lever to bring the RPMs down but it snaps back if I let it go.

 Noticed that my Aquarium Circulation Pumps are still running a bit slow. I checked the voltage frequency and when I set the Voltage to around 122-125v the genny Voltage frequency is only at 54hz... From my understanding the unit should run at 62hz with no load and drop to 60hz with a load to operate loads in the proper range.

 When I adjust the speed control of the engine, she's REALLY cranking out RPMs it seems. (maybe I'm just not used to hearing it run so high as it wouldn't do this before. possibly because of the carb, Spark and air cleaner issues.) when I bring the output frequency to 62hz (no load) the voltage is at 146vAC...? This can't be right can it? I thought that I read somewhere that with no load some gennys are set to run that high and the VR will adjust once a load kicks in...

 I'm not sure where to go from here and I've spoken to a few "Certified" Generac Repair people and they couldn't tell me a thing.

 Any help would be great. 

[tanner0441]

Hi

As you don't know the history of this generator you don't know if anyone has adjusted anything.

I have serviced plenty of small generators and in your case having sorted the fuel, air filter, and plug issues I would load the generator up with something like a fan heater to half way, set the engine RPM to the correct revs, in the UK it is normally 3000 depending on the number of poles in the alternator. I think for 60 Hz it is 3600. once the frequency is set I would look to the voltage regulator and adjust it to the correct voltage.

The I would remove the load and see how much the voltage goes up. Then load the generator to its maximum capacity and see what the voltage drops off to. It is not unusual for a small generator to have a voltage swing of up to 20% between no load to full load. You also need to know the power factor as well because that can have an effect on the voltage swing.

Inverter generators are another thing altogether and the voltage and frequency are independent of engine revs.

Brian

[thirteen]

1 1/2 years ago I started using premium gas instead of regular gas. It helped stop things from running rough under load and if it would sit for 3-4 months I stopped having problems with storage. It won't help your problem but I thought I would pass it on. It made big difference in my chainsaw and gensets.   13

[Flux]

I don't know your particular generator but as its voltage is sensitive to speedI assume it is a capacitor excited version, if it had an avr the volts would stay constant with speed.

The capacitor excited things are very speed sensitive. Assuming it is a 60Hz unit you need to set the speed first and about 61 to 62Hz on no load should be ok, it will drop to 60 on load.

Make sure your frequency measurement is accurate and check with a tacho as a check if you can.

If your speed is set right and the volts are high it is conceivable that it was designed for 50Hz. If it is a genuine 60 Hz unit then almost certainly the capacitor has been changed for one that is too big and you will need to find the correct value to get back to 115v. Try to measure the existing one so you have a reference to work to.

It may be that the capacitor was changed to something near and the engine speed was dropped to get the volts back down.

Can't help with the idling device, not familiar with it. We have the same problem with crap fuel with alcohol added in the UK and it causes havoc with carbs.

You seem to be most of the way there with the engine, the capacitor is the only thing other than speed that affects volts.

Good luck
Flux

[Mary B]

capacitors change value with age as they dry out too so it just may be defective. And a new one off the shelf isn't always the right value of it has sat in a warehouse for years.