generator starts right up but quits

thelonewolf · October 03, 2015, 09:21 AM

My generator. Is a ohan and she starts right up and runs for a min then stops she acts like she is starvin for fuel. But it has plenty. Changed fuel. Filter and carb.

Any suggestions on this madder would be most helpful

Rickf1985 · October 03, 2015, 09:35 AM

Possibly a coil gone bad.

lemortede · October 03, 2015, 09:35 AM

I'll toss out what was causing my issue.
There is a quick shutdown solonoid that was shorting out.
It wasn't evident until the engine was running and the system was powered.
It would extend or stay extended due to the short and kill the engine...like it's supposed to when you want it off.
Beyond that there are a number of things, oil pressure safety switch etc that could be the problem.
Did you download the manual for your generator from the member area. The service manual has a troubleshooting guide.

Bnova · October 03, 2015, 10:34 AM

If you recently did some work to the gen (changed fuel filter and carb), I would go back and double check all your work. Especially if it only started doing this after that work was performed.

When it runs for a "min" and then shuts down, does it start right back up?

And when it's running, does it run well or is it sputtering?

And when it shuts down, does it shut down like normal or is it surging or sputtering?

Also, what model Onan?

DaveVA78Chieftain · October 03, 2015, 01:20 PM

Lots of different Onan models so we have to know the complete Model No. info from the ID plate to help you.

Winnebago · October 31, 2015, 09:21 AM

I'm encountering a similar problem on a 4.0 BF generator (70's model?) Will run great for about 45 seconds, start to surge (hunt?), then shut off. When I attempt to restart--it won't go. I'll leave it for several hours and attempt to start. Will go for about a minute, surge, then stop. Any suggestions? Where to start? How to test? Thanks for any help!

Rickf1985 · October 31, 2015, 09:44 AM

Clogged fuel filter or coil going bad. Replace the fuel filter first, much cheaper and easier.

DRMousseau · October 31, 2015, 12:23 PM

I'm generally inclined to believe these are fuel issues, but I won't rule out the ignition coil matter.

If a coil is really bad, it will cause sever missing and poor starting if at all. A failing coil usually has to "warm up" a bit before internal expansion causes shorting within it, and it then usually begins missing and dies. After cooling down a bit, it may restart as normal, till the coil again, warms to that critical point. This was a common issue in Bakelite (plastic) enclosed coils, that were subject to extreme heat and age that often cracked the enclosure. And not uncommon in early "can" type metal enclosures, where in time, engine vibrations, heat, and age caused internal shorting between the lightly coated and insulated wire coils.

These issues described, running for about 30-40secs or so, surging and "starving" before stopping, and unable to immediately restart, is often a sign of restricted fuel flow for any number of reasons. The location of these generators is usually quite some distance from the fuel tank, and fuel pumps are more efficient at "pushing" fuel then "drawing" fuel over distance. I have a small fuel tank I can connect at various points in the fuel system to bypass suspect components right up to the carburetor if necessary. If the engine starts and runs good with an overhead gravity fed fuel supply connected directly to the carb,... then you'll know the fuel system between carb and tank supply is faulty. This includes fuel filters, pumps, feed lines and maybe an obstructed tank outlet.

If the engine still fails to maintain itself with an auxiliary tank, THEN I'll begin to look at other systems including the carb and float bowl and other problem areas such as the oil pressure switch, cutouts and others.

LJ-TJ · October 31, 2015, 12:44 PM

Well! Just had a similar problem. What a pain in the A*%. This is what I found. First thing make sure you check your oil and it's at the right level. Two things were in play with me. 1) I bought a NEW COIL off E-bay. It wasn't an original Onan coil but one that was suppose to replace the original. Well what it did was fry the new condenser not enough so it wouldn't run, just enough that the generator wouldn't run right. Surge shut down etc. 2) The little push rod that operates the points was worn and allowing oil to come up and deposit oil in the points box and when that happend the points would become saturated in oil and then you'd loose the spark and she'd shut down.
Try and pull the fuel line off after the fuel pump and try to start her and see if your getting fuel flow through the fuel filter and if your are then go up to the carb and pull the line off at the carb. Try and start her again. If you have fuel up to the carb then you no the problem is some were around the carb. Pull the fuel bowl off and see if you've got fuel in the bowl. If you do then you know she's getting fuel. Make sure she's not just burning the fuel that's in the bowl and then running out.

M & J · October 31, 2015, 04:36 PM

After about a minute the choke will open also. Maybe clogged primary jet? Stumbles and stalls since the choke kept pulling more fuel until it opens. Maybe explains why it starts again after it cools off and the choke closes when cooled. Just a thought.

LJ-TJ · October 31, 2015, 05:31 PM

I'm not sure if the gang will get pissed with me posting this site but these guys are the Classic Winnebago and RV's people of Onan Generators. Their a fantastic group dedicated to helping guys like us with our old Onan's. This is not a reflection on Dave and the guys but intended to be another resource. Anyway here goes nothing.
http://www.smokstak.com/forum/index.php?s=7ea4cb38906d95a0754c97106b6ccff0

DaveVA78Chieftain · October 31, 2015, 06:18 PM

Me? Never! I suppose you have not noticed I provide a direct link to the Onan section of Smokstak on the generator manual pages?

BTW - Be sure to download the BF Operators, Parts, and Service manuals from the members area. The fuel pump uses screen filters vs a typical fuel filter.

Rickf1985 · October 31, 2015, 06:19 PM

TJ, I don't think anyone will have a problem with that link, I think it is our resource page anyway. They have the best info around on all old engines.

Winnebago · November 05, 2015, 09:12 AM

Update: At some point in the process, I wasn't able to get the generator to start at all. Checked for spark. No spark. Realized that the F2 fuse was burned out. Replaced. Will start--(but back to the old problem of running for a short while (seconds) then shutting down).

All roads seem to point to the fuel pump. On my model, the fuel pump and filter are within the same piece. When I apply 12v to the fuel pump (by-passing the control board), I might get a single clicking noise and a small squirt of fuel out of the carb side of the fuel pump...then nothing else. Am I correct to think, by-passing the control board and applying direct volts to the fuel pump, that I should notice or hear a consistent pumping or "clicking" noise from the pump? Thanks for your input. There is something oddly addictive and unhealthy in trying to hear that old generator purr again....

DRMousseau · November 05, 2015, 11:00 AM

The pump you have is an solid-state interupter type oscillating solenoid pump. The "click" you hear is the solenoid activating ONCE, with no release. The pump "oscillates on and off" to move a piston inside, against a spring and internal switch to return for the next stroke. The pump and piston has check valves to move fuel flow in one direction. When running properly, it has a constant clicking or tapping sound that many mistake for loose tappet adjustment.

The pump CAN be easily removed to disassemble for cleaning and/or to replace the filter if present. Some had no internal screen filter and required and inline filter BEFORE the pump. While removal of pump is not necessary for filter replacement, it is best to remove for disassembly, inspection and cleaning. A special wire clip retains the piston against spring pressure.

When I disassembled mine, I found some particle matter and surface corrosion that hindered full piston and valve action, and noted some damage to aging seals and valves. I cleaned and reassembled with no further problems SO FAR. But I will have to replace the pump sometime in the near future. The internal solid-state switching mechanism is sealed and not accessible or serviceable.

If after through cleaning, it still doesn't work,.... you'll likely have to replace it. And it isn't a cheap one,... made by Facet.

Rickf1985 · November 05, 2015, 11:24 AM

If the gas line is hooked up to the carb when you are applying the voltage to the pump then it will click only until the carb is full and the needle closes. Once pressure builds up in the line the pump stops. If the line is off of the carb then it should run constantly and flow a steady stream of gas. Even if it is not getting gas from the tank it will still rattle.

Winnebago · November 05, 2015, 11:30 AM

Thanks for the thoughtful response, Dr. M.! Thanks Rick, as well. I will post an update after attempting a new fuel pump...yikes $$$!

Bnova · November 05, 2015, 01:25 PM

I think I would first take the old one off and give a try to cleaning and testing as Dr. M suggested before buying another.

Wayne Thomas · November 05, 2015, 04:39 PM

I had a bad diaode . When mine acted that way .

LJ-TJ · November 10, 2015, 01:03 PM

Ok! I am now in a little better frame of mine thanks to a chap by the name of Rob in a small southwestern Ontario village called Wyoming. As you all know my generator has been giving me fits. Well what I found out was
1) the little push rod that operates the points was worn allowing oil to come up the shaft.
2) I had put in a new generic coil that was suppose to be a replacement coil for the original Onan coil.

Well it seems the new coil fried the new condenser I put in. Also the points were worn. I didn't take Rob any longer four minutes to figure all that out. Seems this isn't to first time he's had this problem with these new replacement coils. The interesting thing was the amount of time he spent setting up the points. When he was finished the old girl really did sound like she did when I'm sure she sounded like when she was new. It runs like a dream now. So if any one is looking for someone who really does know about these old girls you might want to check out Wyoming Tires Plus (519) 845-0813. Oh! $80.00 plus tax. I thought that was a pretty fair price considering I was going to turn it into a boat anchor and purchase a new?

M & J · November 10, 2015, 07:27 PM

thelonewolf · November 25, 2015, 03:10 AM

Hey guess what I replace my generator and yep im old school and low buget on purpose and u all been. Very helpful. And guess what fella IM A GIRL yep. Im a pistol packing mama. And I do everything old school. I work on my own stuff

LJ-TJ · November 25, 2015, 08:04 AM

Awwwwww BUT. Tell us more. What did you replace it with.How'd you replace it? Got any pictures. Remember we're guys. We like pictures. We don't read directions well. :)rotflmao

Winnebago · July 02, 2016, 09:29 AM

Update: I attempted cleaning the old fuel pump with no success. Purchased a new pump and seperate filter (the older pump had these combined). The cost was around $100. The generator seems to run great now! Any advice on fine tuning the generator would be great (there are two adjustment knobs, right?). Otherwise, I love having the Roof ac on while driving down the road. Thanks for all of your input!