Generator out put issues........

[Blueflame6]

I've got a Coleman/Powermate 4,000 watt generator model : PM54A4302 with a B&S 8 h.p. model 194412 engine. I got it from Craigslist last summer (2016)cheap, I went through it, carb rebuild, fuel lines, etc. removed end bell cleaned it up inside (brushes like new), ran well, produced 120v and 240v no problem at no load.....that's the problem. Went to use it this week from the storm as it knocked out the power, started right up, checked the output voltages and Hz good so I plugged it in and the engine slowed down to a point where elec. generation was 90v AC. Removed load, engine went back up fine and voltages were all good again. Even putting a 500 watt halogen work light slows the engine down, voltage to 110v and 60 Hz. A 1,000 watt draw gives me 93v with 56Hz with a nice rpm drop. I checked the governor preset (from my B&S repair book) RPM and set it for 4,250, then set the engine for 3,750 rpm top no load for 3,600 rpm 60 cycles. Then removed the end bell again and changed the capacitor as the old one looked a little "lumpy". Still the same, runs well and produces well at no load. Just wondering if I am missing something?

[lee]

I'd be curious as to what happens if you put about a 50% load on it with a resistive load that low voltage won't hurt like a heater, toaster etc. With the load pulling down the rpms and you looking at your voltmeter, tach, freq meter what happens if you manually open the throttle plate? Does voltage and rpm come up? Is the throttle already wide open and the engine not able to produce any more power? Is the engine surging (lean) or running rough and smoking (rich)? What happens when you remove the load and manually push the throttle plate closed against the idle stop? Does it idle nice and smooth around 1750 rpm? When you let the throttle rod go does the engine return to 3750 rpm nice and smooth? My 5000W PowerMate would stumble when you hit it with a load and richening the idle screw on the side of the carb fixed it. The idle screw on mine controls the fuel at no load all the way from idle to 3750. If it's lean and the throttle suddenly opens due to a load it will stumble. I put at least an 80% load on it to adjust the main metering screw after the idle screw has been adjusted. Hope this helps and it's a carb prob and not a gov or internal engine prob.

[Skywatcher]

Hi Blueflame

The other thing I'd look at on this unit is the spark arrester in the muffler if equipped. I've known these units to run fine at no load, but once a load is applied, the engine can't breathe out properly so stumbles and struggles. Also, as Lee says, look into the carburetor and see if the throttle shaft can actually move to full throttle. Let us know what you find and all the best,

Sky

[KE4AVB]

Here is a thought.

It might be running too lean or too rich. These engines tend to run off the idle carburetor circuits until loaded which they then start pulling fuel from the main mix circuit. This is actually how most carbs work on governed setups with the throttle vane nearly closed off load and then it opens once loaded.

First adjust the idle mixture at idle speed and then adjust the main mixture under load and that should correct the problem if it is fuel related. Otherwise with it being an L-head the valve clearances might be too low causing a loss of compression under load.

Just thinking of possibles.

[Blueflame6]

Good morning, and thank you for your replies, Just finished another test. Throttle shaft works to full throttle. Tested with elec. hot plate and 2 halogen lights for a 1,500 load. RPM @ 3,500, 55.7Hz, and 90.7V. No surging, smoke or running rough. Disconnected load, idles pretty good @ 1,750 (no idle mode here, I did it manually) and back up to 3,750 smooth. With load back on voltage and rpm comes up nice when I manually push the throttle plate to proper speed. Sounds like it will generate alright. I did adjust carb main mixture at load 1/16 turn richer gained a little RPM. It does really run smooth high or low just doesn't ramp up to proper speed when called for. Static governor lever adj. maybe?, spring tension too much? I must thank you all again for your help, any more suggestions are certainly welcome................Peter

[RoyM]

If the throttle is wide open and the engine won't come up to speed there is nothing wrong with the governor. You may have a leaking valve or head gasket.

[Blueflame6]

RoyM, thanks for the reply.....I have the genny set @ 3,750 rpm no load, when a load is applied the engine doesn't ramp up to keep the engine at 3,600/3,750 for good voltage, etc.. I have the top preset RPM set at 4,250 RPM, manually I can bring up the RPM properly to 3,750 and voltage and Hz is good. I was just now thinking the governor wasn't doing its job. Never considered a leaking valve or head gasket. thanks, Peter

[38racing]

seems to me if you can bring it up to speed to match load by manually adjusting throttle then it's not valves but rather the governor. if you know that you'll be running on a constant load for awhile then maybe you can just use the idle speed screw (or a longer replacement one) to get the correct Hz.

[Blueflame6]

38racing, that does make sense, but usually when I use any of my generators (3) there is usually no constant load. Start up and run RPM is 3,750, when a load comes on a dip more than to 3,600ish kicks in the governor, or what I thought is supposed to happen. I set my top governor pre set RPM at 4,250 so it can never go higher, I just wonder if setting it higher than 3,750 may do any internal harm? I will try a higher going to 4,000 RPM for my run speed tomorrow and report what happens. My B&S repair manual doesn't have much detail on the governor itself, just the adjustment for generators.

[lee]

My 5KW Powermate has the Tecumseh 10 HP engine and it doesn't have any way to preset the max rpm to 4250. It would probably throw the rod before it ever got to 4250 or at least burn up whatever was connected to the gen as voltage would be sky high. Did you open the throttle under no load until it hit 4250 rpm and then set a stop screw or bend a tab in order to not let the throttle open any further? If so that may be your problem. On mine you can look in the carb throat and turn the throttle plate until it is wide open. You do this while the engine is running no load and it will rev until it throws the rod as there is nothing limiting max rpm when you manually open the throttle. That said when you put full load on the engine the throttle will be wide open or pretty close and the rpm will be around 3400-3450. By full load I'm talking about a 5kw 240V heating element in a water heater as the load. No load rpm set at 3750. If I somehow set my throttle to only open enough to get to 4250 no load it would do exactly what your's is doing when I put a load on it. I hope I explained this so it makes sense and it helps you out. I've received lots of help over the years from the folks on this forum and it's predecessor perr.com so I like to try to help when I can.