Onan 4BGE run/stumble

[Rickf1985]

I have a 4BGE that will run good for about 2-3 minutes and then it will stumble and go full throttle to try to catch up. When it does this it runs super rich and just stumbles along blowing black smoke unless I push the throttle lever back to idle by hand. If I do that it smooths out. If I manually try to give it full throttle it does the same thing. I have pulled the carb and cleaned it completely, every jet removed and cleaned. The Main setting does not make much difference at all I am thinking I have a coil going bad, is this a common occurance on these? The spec is F so it should have electronic ignition.

Rick

[TheSportsmanDodger]

if voltage is available before shut off.then its not your coil. sounds like its time to rebuild or change fuel type.  if your mixtures wrong then thats why it wont stay on, you could also pull your plug clean it regap it and that will make it fire properly.

[jmerritt]

Are you setting the genset according to the service manual? If not you should get the service manual and follow the procedures in it. I tried to set my NHE without the manual and never was able to get it right. Also you need a meter that will display Hz so that you can set it properly.

John

[Rickf1985]

Settings are per the manual, One manual says 1 1/2 turns on the main and 1 1/2 turns on the idle and the other manual says 2 1/2 turns on the main. I tried both. New plugs and gapped at .025. Float set at .61 per the manual. The float was substantially lower when I took the carb apart and it ran exactly the same so I think I can eliminate the float setting. It simply will not handle a quick heavy load. It is like the gas is there but not atomizing. I would think clogged bowl vent but it is open.

[legomybago]

Black smoke, running rich, and stumble can be the circuit board?? Take a look there too.

[Rickf1985]

Circuit board? I don't see how that would affect the engine running? I am running with nothing hooked up right now.

[legomybago]

Your ignition control board on the genny

[kattkisson]

If yours is like mine it has an electric choke that has a heating element in it controlled to a certain voltage(I think 10 Volts) by the circuit board in the control box.  If this element has a poor connection and is not hot the choke will pull on thinking it is a cold condition.  Check the connections to the choke coil under the protective cover at the carb.  The choke is spring loaded On and needs the heat to pull off.  From what you describe it sounds like you have an intermittent fault. 

[TheSportsmanDodger]

if you heard of obd II, You would know that the COMPUTER SYSTEM is the biggest part of every new car.


so i agree with them, check the circuit board. something always has to be regulated on every engine on every year not unless ita a orginal model T lol

[DaveVA78Chieftain]

1) You said Spec F so you should be only using 965-0528. Stop confusing yourself and get rid of 965-0530
2) Electronic Ignition did not start until Spec G.  With Spec F you have point based ignition.  Ignore all computer related comments for this generator model.   Even for Spec G that is just a ignition module, not an ECM like used in several of today's new generators.
3) Is electric choke sticking or improperly adjusted causing it to run way to rich?
4) Is the choke pulloff not working such that it is running way to rich during warmup period?
5) Is the governer sticking on full throttle (spring to heavy or weak)? linkage binding?  The after 2-3 minute issue sounds like choke opens but the governer is over reacting to the current rpm.
6) Is the carb linkage binding at full throttle?
7) Adjust the choke, then governer (for speed @ Hz) then mixture (per 965-0528)

Dave

[Rickf1985]

OK, In order.
#1 Duly noted
#2 If I have points then that is probably the problem, Where are they located in relation to the coil or carb so I have a landmark.
#3 Choke is working properly
#4 Choke pulloff is iffy, sometimes it works great and other times it hangs closed for a bit. I am aware of that issue and that is not the problem I am facing. Where can I get a replacement?
#5Governor is working fine, it goes full throttle but the engine does not respond so it stays there, on the few times the engine responded the governor snapped right to.
#7Choke is fine and governor is right on 61 hz at no load. Idle mixture has been adjusted all over the board as has the main. Started with main at starting set point and adjusted idle mixture to fine tune the main.

It will run good for a while and then it will stumble and just cannot catch up.
The stumble will happen long after the choke is off and the engine is warmed up and will repeat over and over.  I have tried many times to to to determine if it is a fuel issue or an ignition issue that causes the stumble. I think it is ignition because it is sudden, itdoes not act like it is running out of gas. Now that I am told it has points I believe that is a definite possibility. Worn points will cause a sudden miss and and large change in timing.

Where can I get points and other parts fast? I have a trip coming up in three weeks and I have found that the rear tires are also bad. I am at the point where I need to decide whether to keep going on this money pit or just put my slide-in on the truck and get that ready in a hurry and dump the class A and cut my losses. The only things I have found that work on this POS so far is the heater and the AC. I have very limited funds and I have sunk way to many of them into this as it is and it has never seen the road yet.

Dave

[DaveVA78Chieftain]

All parts info is from parts manual 965-0231 available in Members Area
Google using Onan P/N for best deal
Most will also be on EBAY.  Onan is proud of their parts ($$)

#2 If I have points then that is probably the problem, Where are they located in relation to the coil or carb so I have a landmark

When you're on the oil filter/carburetor/control box side of the genset, there will be a rectangular sheet metal box on top of the engine, about 1"x4"x2"high, located at the right-hand end of the engine portion of the genset, midway from front to back.  The box will be held down either with a wire 'bail' that needs to be pried side, or with one screw thru the top. If you remove the box/point cover, you'll see the points and condensor. Point gap should be .016. You can turn the engine and generator by hand with a 3/8 allen wrench in the rotor thrubolt, middle of right-hand end of genset.

965-0328 Page 6-12
Points: 160-1183
Condensor inside breaker box (prior to 9/87): 312-0246
Condensor on Generator adaptor (9/87 on): 312-0256

#4 Choke pulloff is iffy, sometimes it works great and other times it hangs closed for a bit. I am aware of that issue and that is not the problem I am facing. Where can I get a replacement?

P/N 146-0589

When it does this it runs super rich and just stumbles along blowing black smoke

Yes over rich mixture.  Recheck the float adjustment.  To much fuel in the bowl will cause it to flood.   Are you using the stock fuel pump?  If not, then pressure range is 4-5 psi.  Anything greater will force the needle valve off it's seat resulting in a flooded condition.

Dave

[Oz]

Here's the link to generators in the resource section:

http://www.classicwinnebagos.com/forum/index.php/page,page4701.html

[Rickf1985]

Thanks Dave, I will look for the box again. That was where I thought it was but all I saw there was the intake manifold which appears to cover the whole top of the engine. I am probably going to end up unbolting the carrier and sliding it out so I can see what I am doing. Everything is easy wiring wise except the 110 wiring which is tight. The float setting is dead on at .610. It was a quarter inch lower than that before and ran the same or a bit better, maybe I should put it back to the wrong setting. LOL. They give a range of .040 to play with and it was .250 off and ran. Go figure. By the way, I set it with a dial caliper so it is actually .6101 but I don't think the extra thousandth will matter.

Mark, Thanks for the link, I can never find that stuff when I need it.

I am in the decision making process right now as to whether to keep it or get rid of it so after I get several loads of wood this week I am putting my slide in on for the trip in May. The missus wants to keep it but I have about had it, I see no end to the bleeding. I have to put 1600.00 worth of tires on my pick-up next week so it is real hard to justify  another 2,000.00 for a R/V which will rot the tires long before wearing them out. The tires that are on there are brand new Michelins with the nibs barely worn off and all four back tires are dry rotted!

[DaveVA78Chieftain]

It was a quarter inch lower than that before and ran the same or a bit better, maybe I should put it back to the wrong setting.

0.59 to 0.63 is with gasket installed

If the gap was .61 - .25 = .36 then the engine would run rich as the fuel level would be higher in the bowl. (point where float closes the needle valve)

If the gap was .61 + .25 = .86 then the engine would run lean as the fuel level would be lower in the bowl.

Given that a carb only uses atmospheric pressure to suck the fuel out of the bowl, the level is critical to proper operation.

For ref, here is a video of a typical set of Onan points (not sure what engine model it is though)

http://www.youtube.com/watch?v=xL5swQNfD-8

The box goes over them.  Please note that the even if it was electronic ignition, I am fairly sure the box would be in the same place.

Dave

[Rickf1985]

Dave, Being a retired master mechanic that specialized in carburetors and electrical I could have a lot of fun with you on this one. There is no such thing as "sucking" the gas out of the bowl. It is delivered by negative pressure produced by the manifold vacuum and atomized by the venturi effect in the carburetor. W% W% Sorry, Just had to. This whole RV is getting to me and I need a release from it. Now I find the wipers are not right. N:( I'll address that in another post. I looked around in there and I did see the points cover, it is going to be a bear to get with the unit in place but I think I can do it with a mirror. At least get the cover off and see if they are points and if so the condition of them.

By the way, when I said lower on the float I meant lower fuel level which should have run lean but did not, it ran basically the same as now.

[DaveVA78Chieftain]

Dave, Being a retired master mechanic that specialized in carburetors and electrical I could have a lot of fun with you on this one.

Now that I know you are a retired master mechanic   W%    .....
You already know all the simple and not so simple stuff.

Normally I try to talk to the general audience who most likely has no clue of the theory behind a carburetor.

Dave

[Rickf1985]

Let me put it this way, I never knew it all when I was an active mechanic and I was never afraid to ask for help if I needed it. That has not changed one bit. If you knew it all then you were full of it! and not knowledge.  W% Master mechanics did not do a lot of work on RV generators, actually this is my first!!! A have done a lot of small engines and the basic theory is the same but they all have their nuances. I never worked on a class A before I bought this thing. Never had a shop big enough to put one in and did not have enough room in my lots to have a monster like that taking up room for an extended time. Class C was the biggest RV I worked on. I did do diesel work for others but again, no RV's. So master or not, here you are my teachers.

Rick

[M & J]

Sometimes we call Dave Sensei.

[ibdilbert01]

Being a retired master mechanic

Why is it always the retired mechanics asking for mechanical help?    D:oH!

[Stripe]

Sometimes we call Dave Sensei.

Indeed..
Wax on....  Wax off....

[Froggy1936]

Yea , That makes no sense ! To Me ! Frank Hm?

[Stripe]

The Karate Kid (Original, not remake)... 

[Rickf1985]

Why is it always the retired mechanics asking for mechanical help?    D:oH!

When I first joined I offered a lot if advice on engines and engine modifications for mileage since that was what I built for people. I also got involved with a questionable modification asking for proof and things got testy. I was banned for a while and since then I keep my engine and driveline  expertise to myself and ask questions about the things that are RV related that I am not familiar with. Like I said, I do not know it all and never will, none of us do. We are always learning. I will offer advice on vehicle wiring and carburetors since they were my specialty and engine repairs but that is it.

History lesson over, back to generators.

[jmerritt]

#7Choke is fine and governor is right on 61 hz at no load. Idle mixture has been adjusted all over the board as has the main. Started with main at starting set point and adjusted idle mixture to fine tune the main.

On my NHE governor no load adjustment should be at 63 Hz max and at full load 58 Hz min. Not sure this would make the difference with your problem but thought I would chime in. I know my genset will hunt badly if the governor idle and mixture screws aren't just right. Also, I had to replace the governor spring on mine since it was getting sloppy and causing bad adjustment.

John