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Engine quits after 3 seconds


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10-28-04, 08:38 PM   #1  
Engine quits after 3 seconds

I have a 1995 Murray push mower with a B&S Diamond Plus 4.75 engine. It has worked nearly flawlessly until today. I push the prime bulb 3 or 4 times as normal, pull the recoil, and it starts. After 3 or 4 seconds, it dies. Repeat the process, same result. I can keep the engine running if I keep pressing the prime bulb.

I took off the air filter over the carb and sprayed some carb cleaner into opening. The engine runs as long as I keep spraying the carb cleaner into it. I took off the filter-holder thing which also contains the tube that carries the gas/air mixture into the engine (pardon my lack of terminology) and cleaned it thouroughly. I reinstalled this piece and tried again, only to get the same result. This leads me to believe the problem is somewhere between the gas tank and the carb itself.

Is there anything else I can do before I drain the gas tank and/or take apart the carb? TIA

 
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10-29-04, 01:03 AM   #2  
Hello DIYnovice!

I believe you need to disassemble and clean the carburetor.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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10-31-04, 05:58 PM   #3  
Thanks for the reply. I've never done work on a carb before, but I ordered an overhaul kit from an online store for about $13. I figure since I'm taking it apart I might as well replace the parts and hopefully get another 9 years of life out of this mower. I've read the FYI at the top of this forum, but do you know of any online resource that shows a general pictorial of the steps needed to get a bowl carb apart and more importantly back together again? I have searched to no avail...Thanks again!

 
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11-02-04, 12:08 AM   #4  
I have no link of pic or procedures, but don't fret over it. It's extremely simple and very few parts involved. Just the carb bowl and screw, float, hinge pin, and needle. Just make a drawing of how the throttle linkage is connected so you know how it goes when reinstalling it. If you run into trouble, we'll be here.


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11-04-04, 09:08 PM   #5  
Thanks again for the reply. The overhaul kit included a small sheet of instructions. I was able to match up most of the parts from the kit with the existing ones. I did not replace all the parts, however (see below). I reinstalled the carb but could not get the engine to start at all. I haven't done much troubleshooting yet except to let the parts "air out" in case there was excess carb cleaner in the engine of intakes - that didn't help. There's a few things I'm unsure of:

The kit included three welch plugs, 2 small ones of the same size and one large one. I could only locate two plugs on the carb. The large one was located on the bottom and had a "notch" next to it that made it easy to remove. I replaced this one and flattened it with a punch - which slightly caved it in. The other plug was located on the side and was fully enclosed (no notch) - I was not able to get this one out. The instructions also indicated that the plugs should be sealed with a non-hardening sealant like finger nail polish. I didn't apply this to the one I replaced since it wasn't air tight to begin with due to the notch. Could these issues with the welch plugs cause a non start?

The kit included 2 small foam washers and one large one. I could only locate one washer on the carb, which was located as part of the assembly that controlled the throttle plate. I didn't replace the washer since I couldn't figure out how to get the assembly apart. I don't think this is the problem because all the parts seem to move freely.

While the carb was apart I cleaned every part and orifice with carb cleaner. All gaskets were relaced. float needle and seat replaced. Idle mixture valve and spring replaced and returned to its original position. No other screws were adjusted during the process.

Additionally, fuel line was removed and cleaned. Fuel is only a month old. Spark Plug is new also.

I'm not sure where to begin with trouble shooting. Any ideas? Thanks again

 
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11-05-04, 07:16 AM   #6  
update

I can get the engine to start if I spray carb cleaner into the carb and immediately start it. Runs for a few seconds then quits. Pressing the prime bulb does not have any effect whatsoever.

 
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11-05-04, 06:43 PM   #7  
Any chance you got the float in upside down? Sounds like the carb may not be filling with fuel.


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11-05-04, 07:58 PM   #8  
I took pictures of each part as it was removed so I'd have something to reference when putting it back together. The way the float needle inserts into the slot of the float it doesn't seem possible to insert the float upside down.

Picture: http://im1.shutterfly.com/procserv/4...47580000001610

Any other ideas?

 
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11-06-04, 12:53 PM   #9  
Azis
Posted By: DIYNovice
The kit included three welch plugs, 2 small ones of the same size and one large one. I could only locate two plugs on the carb. The large one was located on the bottom and had a "notch" next to it that made it easy to remove. I replaced this one and flattened it with a punch - which slightly caved it in.
There should be passages under this plug, is it possible the plug is not allowing fuel to pass? I have never seen a schematic for these carbs but it was my assumption that the welch plugs are removed to access the fuel passages.

At any rate if after your repair, you have more complications than b4, work at getting back what you have lost and in the process may solve the other problem.
The pic of the float was awesome, use more for any questions you have

 
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11-06-04, 02:33 PM   #10  
Finally figured out why it wouldn't start. The refurb kit included an extra gasket that matched the shape and bolt holes on the front of the carb. This gasket didn't exist on my particular carb - instead a gasket was attached to the plastic filter holder/prime bulb mechanism that is bolted tot he carb. But I installed it thinking this is obviously where it should go without regard to the fact it wasn't there to begin with. I removed the whole carb this morning and found that this gasket was covering up the fuel jets! DUH lol. I'm not sure where its' supposed to go, hopefully it wasn't meant for this particular model.

The engine was then able to start cleanly, but ran very hard. I made some adjustments to the mixture needle and got it running a *LITTLE* better. While observing the parts in motion while the engine ran, it seemed that the spring that was part of the governor linkage *MIGHT* have been stretched a bit during its removal or reinstallation. I used a needlenose pliars to squeeze it a bit and take out some of the play at the ends. This made the engine run incrementally better, but from my recollection still wasn't at optimum speed and it would still sputter once in a while. It also quits if I take it off of full choke. However, I decided to try it out and actually cut some grass with it. It went through tall grass without bogging down much. I'm not sure what to make of it. The mower as a whole now works like its supposed to, but technically the engine doesn't work the way it's supposed to. Not sure where to go from here, maybe I should just leave well enough alone?

Here are some pictures I took from before the refurb:

Pic 1: http://im1.shutterfly.com/procserv/4...4efa0000001610

This is the best pic I had that encompassed most of the carb parts. What is the purpose of the adjusting screw that I drew an arrow pointing at? It's not attached to the carb itself. Turning it clockwise pushed the lever thingy to the right, which only made the engine down, CCW had no effect since the screw eventually stopped touching the lever thingy.

Pic 2: http://im1.shutterfly.com/procserv/4...cf3d0000001610

This is where the extra gasket was placed. It covered up the jet just below the left hole.


I can take and post pictures of any part that might help make a diagnosis, just let me know. Thanks again for all the help!

 
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11-06-04, 10:41 PM   #11  
Check the screw that holds the bowl on the carb. It has tiny holes in it, through the side and down the center. Make sure they are completely clear...that sounds like where the problem is.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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11-11-04, 08:23 PM   #12  
Hi cheese, I checked that screw on the orginal inspection and blasted out the holes - they all seemed to be clear.

But something remarkable happened since my last post. I used the mower to bag leaves for about 2 hours a few days ago. By about half way through the engine was running like it used to before the problems started, and I could even set it to idle and keep it running. It's as if the engine fixed itself! Not sure what to make of it, but I certainly am not complaining! LOL

 
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11-12-04, 12:11 AM   #13  
Great! There was still some trash in the carb causing a blockage and it finally pulled through.


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