engine starting & running problem

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  #1  
Old 04-12-04, 06:54 PM
Grandmaster
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B&S engine problem

Hi All,
I am experiencing a frustrating problem. I have a Murray lawnmower with a Briggs and Stratton 5.75hp quantum engine. Recently the engine has been doing the following: Prime carb, pull cord, engine starts-up and dies. I have done the following to try and remedy the problem: cleaned carb, used compressed air to blow out all orifices and jets etc replaced all serviceable components on the carb and replaced all o-rings and gaskets and the air filter and spark plug. Put it all back together and still experience the same problems. For further troubleshooting did the following. I placed my thumb over the carb and pulled the cord and suction seems to be good. If I hold my thumb over the carb allowing only the slightest amount of air to get by, I can start the engine and it will continue to run until I remove my thumb. Gas is flowing well from the tank to the carb and the bowl is filling up as well. I am really at a loss as what to look at next. Any ideas? Does it sound like the carb is the culprit? Any help would be much appreciated.

Thanks,
Louis
 
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  #2  
Old 04-12-04, 07:08 PM
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Yes it does. I think you need to adjust your carb. Adjust your carb untill it runs properly and let us know how it goes.
 
  #3  
Old 04-12-04, 09:42 PM
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I'm assuming that you have checked to see if the choke is working OK. It wouldn't be unusual for you to need some choke on the engine until it warms up a little. That effectively is what you are doing with your thumb by blocking part of the carb throat. If your choke is OK then your float level may be too low.

Since you must hold your thumb over the carb throat in order to keep the engine running, that says to me that you need a little additional suction go coax the gas up from the bowl into the throat of the carb. It's a common problem and easily adjusted. I don't happen to have a spec from your particular carb because I don't know what kind you happen to have. I do think that the float level should be checked however. You usually just use a ruler or a known sized drill bit to measure the distance between the edge of the float and a point on the carb.

Anyone else have any other ideas??
 
  #4  
Old 04-12-04, 09:42 PM
Grandmaster
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Thanks for the reply. As far as I can tell the carb has nothing to adjust. There are not any adjustment screws on the carb at all...so I am not really sure what there is to adjust. I just looked up the carb on briggs and stratton's website and it lists it at $32...so I guess I will try to find a repair center that stocks it here and see if that fixes my problem.

Thanks,
Louis
 
  #5  
Old 04-12-04, 09:55 PM
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Hello Grandmaster!

You have a restriction in the carb still. (it has no choke, and it has no adjustments...even the float height). Some of these had a hole in the bowl screw. Did you check it and clean it out too? You may have to remove the carb and soak it in carburetor cleaner to clean it out.
 
  #6  
Old 04-12-04, 10:13 PM
Grandmaster
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Hi Cheese!

You know, come to think of it I think my bowl screw did have a hole in it...and it is probably the only thing I did not clean or blow compressed air through. I will check that in the morning before resorting to buying a new carb...or a new honda or toro mower!

As far as carb adjustments, the float does not appear to be adjustable. The float is held in by a loose pin and the float valve slides into an indention on the float. Nothing appears to be adjustable. This engine uses a primer bulb and no choke. That is what has made this so frustrating...there is nothing to the carb...but it will not work!!!!! If it is that little hole in the bowl screw I am going have a good laugh!

Thanks!
Louis



Originally posted by cheese
Some of these had a hole in the bowl screw. Did you check it and clean it out too?
 
  #7  
Old 04-13-04, 08:22 PM
Grandmaster
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well, I just wanted to say thanks to all those that responded. Cheese...you da man! That darn hole in the bowl bolt was clogged! Sheesh!

Thanks All.

Louis
 
  #8  
Old 04-13-04, 08:29 PM
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Great! Glad we could help!!
 
  #9  
Old 04-21-04, 06:49 AM
Sophie_Sundown
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Angry Starting & running problem dido, however.....

....I think I can top Grandmaster's problem. So, hopefully Cheese, Terminator or Jughead will come to my rescue! (or anyone who can help)

The mower: MTD Self Propelled, 6 HP/21Ē Cut Briggs & Stratton Engine (Rear Bag/Mulcher)

As in Grandmaster's post, I also have a problem with the engine starting and then dieing out. Here's what I have done: thoroughly cleaned the carb (with carb cleaner for the third time - it was really nasty the first go around) and replaced the components using a carb overhaul kit (the hole in the bowl bolt is not blocked), replaced the gas tank, fuel line, spark plug, and air filter. The oil is clean and at the 'full' line. Iíve also added a fuel stabilizer.

Each time I have put it all back together, the engine sounds like it wants to start but only will if I put gas directly into the carburetor and then it stops running once that fuel is used up. It will also start with carb cleaner in it. (?) I thought the problem was the gas line or tank so I replaced those but still does the same thing. As far as the primer bulb, I can hear suction but can't see if gas is being sucked in because of the air filter's casing which is where the primer bulb is located. There would be no choke with a primer, right?

In reading the article titled 'Basic Carburetor Information' that is at the beginning of posts for this forum, there is a mention of 2 screws to adjust high speed or low speed. Where are these and do you think they are related to my problem? or... Where are the idle needle, adjusting screw and mixture valve located and should I concern myself with these?

Perhaps it's related to the throttle?? I say this because what I think is the throttle seems to be very loose. What I'm referring to is the metal wire that connects to the top of the carburetor. Would adjusting the throttle be part of what is called "adjusting the carburetor" as suggested in WimbeldonWoman's post? Is the throttle shaft the same as the choke shaft?

The shop where I've taken my other dead mower for service and where I've bought parts has provided some help...one suggestion was to make sure to replace the little red rubber gasket that the float needle rests in. I did that last night and haven't put the mower back together yet. It just seems like such a minor thing and Iím not messing with this mower anymore once I put it back together.

The owner's manual is pretty much useless because for most items that it references, it states in parentheses "if equipped" behind the listed item. Though the manual is supposedly for this model, the diagrams don't look like my engine so itís hard to tell what itís equipped with. And.... what is up with the Briggs & Stratton's carburetor kit suggesting the use of nail polish to seal the Welch plug?? I did and it didn't affect anything yet so maybe it's not so odd.

Sorry.... I know you're probably getting as frustrated as I am and I should just take it in for service but I've spent too much time at this point and it's also too heavy for me to lift. Plus the cost of the service and having them pick it up will cost me the same as buying a new one - which is what I did last night. However, it was more of a p.o.íd buy and donít want to spend the money when Iíve come this far so Iím adamant on not taking it out of the box until I've exhausted all measures with this monster. Besides this mower is my ex's and I sort of look forward to mowing over the dog poop that I missed hidden in the tall grass! (Yes, I need a life.)

Any ideas and/or suggestions? Anyone want to buy a lawnmower? Thank you VERY much in advance.....

Sophie
 
  #10  
Old 04-21-04, 09:22 AM
Grandmaster
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Hi Sophie,
I am no expert, but I think your problem is still carb related. You said it was pretty dirty when you first took it apart so assuming fuel is making it to the carb and filling the bowl, then I think there must still be something clogging something somewhere! I assume that every time you have taken the carb apart there has been fuel in the bowl indicating that fuel is making it into the carb. If you have an air compressor I would blow air through every orifice just to make sure there is no blockage. Also on the bowl nut, when I removed mine I blew through it and thought it was not blocked...but I blew compressed air through it anyway and that seemed to be my problem. Also when re-assembling it make sure that one of the 2 holes in the side of the bowl bolt align with the notch in the carb when tightened. Hope this helps...or at least gives you something to do until Cheese tells you what is really wrong!

Louis
 
  #11  
Old 04-21-04, 09:27 AM
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Incase you don't know this, when you tighted your bowl screw back on, the rule of thumb is tighten till seated than back off 1/2 turn. Thanks...
 
  #12  
Old 04-21-04, 11:17 AM
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Before you back off any "bowl screw", be aware that there are no adjustments on this carb. If you do back the bowl nut off, it will leak fuel. Don't do this. Back to your problem! You said you cleaned the carburetor in a cleaner. My concern is whether this cleaner you used is sufficient. Spray cleaners just don't cut through well enough in heavy varnish build-up. I recommend using NAPA product # 6401, carburetor cleaner to soak the carburetor in. You will have to strip the carburetor down again in order to soak it in this cleaner, as this cleaner will ruin any rubber parts. Soak for only 20 minutes and be sure to use protective gloves as this cleaner is caustic.
 
  #13  
Old 04-21-04, 11:03 PM
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I agree...soak it in carb cleaner. Don't back off the bowl nut unless you are removing it. It needs to be snug, otherwise you'll have a fire/explosion just waiting to happen. I think terminator is thinking of a high-speed adjustment screw, which your engine does not have. You have no adjustments, so the info about the 2 screws in the "basic carburetor information" you read does not apply to you.
 
  #14  
Old 04-22-04, 05:03 PM
Sophie_Sundown
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I soaked in carb cleaner the 2nd go around....

....the cleaner is Champion Heavy Duty. And used it again the 3rd time to spray the surfaces and inside. Puey: Is this a comparable brand to NAPA? (The first time I used cheap stuff from Walmart...actually I've probably taken it apart 5 X or so and cleaned it each time.)

Grandmaster: What do you mean by aligning one of the holes in the bowl nut with the notch in the carb? I'm not sure I understand which notch.... ("then I think there must still be something clogging something somewhere!" - ha, ha! ‹)

I will use compressed air for the little holes and the bowl nut.

Cheese: Could the throttle have anything to do with my problem or is that also not in need of adjusting? It seems loose.

Terminator just wants to put me out of my misery....

Thank you for your responses. Compressed air and reassemble. Yes, I'll probably take it apart again if I have not luck!
 
  #15  
Old 04-22-04, 06:02 PM
Grandmaster
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Hi Sophie,
It is possible that my carb may have differed from yours so my advice may not hold true. I am also not sure of the proper terminology for everything but I will try to convey my message as best I can. On my carb, the bowl bolt threads into a center post(lacking the proper terminology here...but is basically the threaded place the bowl bolt threads into) of the carb. When the bowl is attached to the carb, the indented bottom of the bowl sits flush with the bottom of the post, except for a little notch in that post. The fuel, I assume, flows from the bowl past the little notch in the post, through one of the 2 little holes in the bowl bolt, up the center hole in the bowl bolt, up through the main jet and then into the engine. I used a marker to mark the bolt head with the location of the 2 holes and the bowl where the notch was at. If I were to have tightened the bolt till it was super tight, the hole and notch would not have been in alignment.

Of course my disclaimer is I am not an expert, shadetree mechanic at best...so it is likely that I have no clue what I am talking about!!

Louis
 
  #16  
Old 04-23-04, 12:58 AM
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You don't have to worry about the hole and the notch. The screw has a relief cut into it...an un-threaded area...that allows fuel to enter the notch and work its way through the hole no matter what position it is in.

The throttle should not affect the problem you're having.

The carburetor cleaner we are talking about comes in a bucket/pail. It has a basket you put the carb in and lower it into the solution and let it soak. This is vastly different than the spray type carb cleaner.
 
  #17  
Old 04-23-04, 06:42 AM
Sophie_Sundown
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Lightbulb Okay.... I may have found the culprit

Thank you cheese, I have a much better idea of what you guys are talking about. So then I guess it wasn't a good idea to soak it in my bathroom sink? ‹

Louis, I completely understand what you are saying....probably because I haven't a clue on technical verbiage either. Don't take offense if I go with cheese and 'X-out' the alignment of the notch and one of the two holes on the screw.

After tonight, it may take me a few days to get back to you guys with the status. I'm not giving up - I fractured my elbow wednesday night so I am moving pretty slow plus I have relatives coming in tomorrow.

ANYWAY..... I may have figured out what the culprit is: I'm having a major problem with the plate that has holes and tabs in it and is screwed onto what I think is the throttle shaft. According to the carb overhaul kit, the tabs are supposed to be on the bottom and the numbers on the plate face outward, away from the primer bulb and fuel intake place. I cannot get it to sit right in that position. I can get it in that position but then it doesn't move freely or open and close I guess it's referred to. It only spins halfway to closed or whatever. Like it's stuck on the side edge of the top and/or bottom shaft holes. Making any sense? I'm sorry!

It moves perfectly with the tabs on the right side or on the top. Also, are the holes supposed to be free and clear of the shaft?

It was a little bent and I very carefully tried to straighten it. Will this prevent it from ever working right? It wasn't supposed to be bent was it?

Can I take the plate (if similar) out of the other dead mower's carburetor and install it in this one? Didn't one of you guys price a B&S carb at $30 or something?

Think Lowes would notice the carb switched out? (I'm kidding...)
 
  #18  
Old 04-23-04, 10:59 PM
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Is the plate you're describing inside the throat of the carb? If so, it shouldn't be bent. Try loosening the screws that hold it on, and see if it will close all the way then. If so, hold it in the closed position and tighten the screws.
 
  #19  
Old 04-26-04, 11:58 PM
Sophie_Sundown
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plate...

yes, the plate is inside the throat of the carb. It will only close if the tabs or holes are in the wrong position. According to the overhaul kit, the tabs should be at the bottom. No, it will not close if the screw is loose, only when out of position.
 
  #20  
Old 04-27-04, 12:41 AM
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It's hard to tell just by text (without actually looking at it), but might need to turn the shaft 180 degrees, and install the throttle plate that way. It should completely close...enough that you can't see a gap around the edges of it. Look at the one on the dead engine you have and note which way it is installed.
 
  #21  
Old 05-04-04, 10:14 PM
Sophie_Sundown
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Question

Well, I checked out the carb in dead engine (can't use the plate for this one) and it doesn't have the holes or tabs that this one has. According to the overhaul kit directions, the holes are supposed to be on the bottom after installed. That's why I'm trying to get it to close without turning it.

What do you mean cheese by turning the plate and the shaft 180 degrees? The shaft sets in a cut-out in the throat of the carb.....

(I busted out the new mower but still want to fix these two, or atleast this one)
 
  #22  
Old 05-04-04, 10:28 PM
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By rotating it, I mean turn the shaft around half a turn. It's hard to describe, but if the wrong end of the plate is installed first, it will not function properly. One end of the plate will go farther into the carb throat than the other end, and if you have it the wrong way, it will not open and close all the way, or possibly won't close enough. (when you open and close the butterfly plate, one end goes into the carb throat and the other moves out toward the opening. If you have the ends turned around, it won't work, or if it is opening from the wrong side of the throat, it won't work).

I hope you can make sense of this...as I said, it's hard to describe.
 
  #23  
Old 05-04-04, 10:49 PM
Sophie_Sundown
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Question

but the plate is round.... Do you mean flip it over?

I know it's hard explaining it so thank you for your attempts! I just hope I'm making sense of what you're saying...
 
  #24  
Old 05-07-04, 12:46 AM
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I wish I could come up with some kind of better way to describe this, but try to follow me. Picture this " l l " be the carb throat, as if looking down at it from the top of the carb. If the throttle plate " / " is in like this ...l/l , then try reversing the position of it like this.... l\l . The shaft should have a spring that makes it return to one position when you move it, and release it. It should make the plate close when you release it.
 
  #25  
Old 05-09-04, 06:45 PM
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Were you able to figure this thing out?
 
  #26  
Old 05-11-04, 05:24 PM
Sophie_Sundown
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Thumbs up got it...

dig... I'm hearing you now. I'll check it out and see how it sets. I probably won't get to it for a few days. (I think I mentioned that I decided to use the new one but still want these 2 as a pet project so to speak.)

Thank you again - great explanation!

Any idea how to remove thinset? (without chipping it away by hand or using a grinder that might tear up my concrete below it) - I've posted in flooring with the ?
 
  #27  
Old 05-11-04, 05:27 PM
Sophie_Sundown
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sorry terminator, I didn't see your post. My comp didn't show it for whatever reason.

I'm going to check it out and will post what I find and if cheese's suggestion works for me. It may be a few days though....

Thanks again all!! I'll 'talk' to you soon...... (fair warning ‹)

Sophie
 
  #28  
Old 06-19-04, 07:38 AM
Sophie_Sundown
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Just an FYI

I have set this project aside for now.... at least until I can get all of my lawncare stuff in order (along with the rest of my house).

I'll be back though....

Sophie
 
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