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Murray lawn tractor - wont start

Customer Question
Murray lawn tractor issue- Problem...
Murray lawn tractor issue- Problem still exists with the motor. It turns over but doesnt ignite. Voltage has been checked to all points and shows at 12.4 volts. I have jumped the safety switches as well. When I pour a little gas into the intake it will start up and run for just a second then quit. Also, the headlights do not turn on from the ignition switch but they do when I apply direct voltage to their lead. I'm thinking that I still have a safety swith issue somewhere or a ground not making good contact somewhere. Help is still needed on this problem. Thanks
Submitted: 6 years ago.Category: Small Engine
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Answered in 28 minutes by:
9/2/2011
Technician: James W, Small Engine Troubleshooting Expert replied 6 years ago
James W
James W, Small Engine Troubleshooting Expert
Category: Small Engine
Satisfied Customers: 3,708
Experience: 7 years as Mechanic & Parts Manager for Brother who has Owned Lawn & Garden Repair shop for 35 years
Verified

James W :

Greetings, My name is James W, and I am here to help the best I can. My goal is 100% satisfaction. Let's get started.

James W :

Sorry for the delay

James W :

You DO have a carburetor issue of some sort

James W :

it could be dirty and need cleaned, and I can provide you information on how to do that.

James W :

but playing a hunch, and hearing you mention the possibilty of a voltage related problem

James W :

I also would like you to test a component on the carburetor called an afterfire solenoid

James W :

its purpose is to shut off the flow of gas through teh carb when you turn the ignition off

James W :

to prevent backfires

James W :

It must have 12V at all times to opperate

James W :

when you turn the key on to run, you should hear a tiny click coming from this relay on the carb

James W :

if not, we are sure it is not working

James W :

test to see if there is 12V going to it when the key is on

James W :

Also, check to see if when 12V is applied to the solenoid that the plunger retracts the extends when it loses 12V

James W :

Yes, the solenoid could be bad.

James W :

BUT, another explanation could be that PART of the starter switch is defective

James W :

Or any one of the wires attatched to it could be bad.

James W :

I put $5 on the starter switch if I get good odds

Customer :

I have some questions for you

James W :

dialogue is open

James W :

I now see that you had a second question answered here also

James W :

I am now reading it...

Customer :

Why would it be the a carb issue?

James W :

When you pour gas into the carbh, it runs, and dies when it runs out of the gas you poured in...

James W :

Very much classice dirty carb problem

James W :

But if the carburetor afterfire solenoid is defective, it will have similar symptoms

James W :

ALSO, 80% of the time you have a defective fuel solenoid, you ALSO have a dirty carb because the gum and varnish of old gas either caused the solenoid problem or exasserbated it.

Customer :

Where is that located on the motor

James W :

ON the Carburetor

James W :

Not all engines have it.. But mose of the tractors do now

Customer :

Does the Murray lawn tractor have it?

James W :

Here are few pics of the various types of them

James W :

Murray made 10000 models of tractors before they went out of business

James W :

some did, some did not

James W :

if you have the model number and type number and serial number of THE ENGINE

James W :

I will be able ttell you If and wher it is

Customer :

I don't have the model with me right now.

James W :

that is OK

Customer :

I have replaced the ignition switch and the starter solenoid already

James W :

Let e send you some information on the carb cleaning process

Customer :

doesn't it seem strage though that the headlights do not come on via the ig switch but they do when you apply 12 v to their lead?

James W :

Then you an try it out and get back with me when you are nearer your unit

Customer :

Wouldn't a bad ground somewhere in the harness also prevent the ignition from occuring and stop fuel to the carb as well?

James W :

That is why suggested the starter swithc issue

James W :

ALSO possible the WRONG switch was put on

James W :

there are at least 6 tyupes

James W :

types

Customer :

It's a 7 pin switch

Customer :

looks identical tot he one I took off of it

James W :

A wrong starter switch WOULD 100% explain the fuel solenoid and lights both not working

James W :

Muse Match INSIDE

James W :

must, I mean

James W :

The POLES have to be labeled exactly the same pin for pin

Customer :

Is it possible that there are different 7 pin configurations on switches?

James W :

they have to be wired the same inside

James W :

YES

James W :

Where did ou get the switch

James W :

and how did they determine it wsa the right one

Customer :

Understood. I get the same reaction when I use either switch, the old one or the new one. It cranks but wont fire.....and the headlights do not turn on.

Customer :

which would tell lean me more to a grounding issue possibly

James W :

Then t very well may be a wiring harness problem

James W :

u get to check iINCH by Inch by Inch

James W :

feeling it, unhooking and rehooking it up

James W :

making sure no insulation is bare

James W :

and all contacts work fine

Customer :

can the ignition switch be bypassed in order to get the motor to at least fire and run?

James W :

o corrosion

James W :

messy

James W :

YOU said, it runs when you put gas in it

Customer :

briefly. Unitl the gas is used up.

Customer :

when i put gas into the intake it will run for a sec

James W :

Before we go too far, you need to check the after fire solenoid

Customer :

so I know there is ignition in the chamber at least

James W :

if there is 12V to the afterfire solenoid, and it runs with gas poured in, then

James W :

bypassng the starter switch will make no difference

James W :

You y have more than one problem

Customer :

it only runs until the little amount of gas I put into it is used up. Then it quits

James W :

but start with checking the 12V to the solenoid and then check the solenoid

then get back to me

James W :

I wil notified via email of yur replies

James W :

nd to start a new question up

Customer :

Do you have a picture of what the solenoid looks like on the carb?

James W :

j come back here

James W :

sorry

James W :

I thought I had sent it to you already

James W :

here are several types

James W :

about three ays they mount depending on which engine and which carb

James W :

two ways of wiring depending on the year

James W :

wire or t

James W :

two

Customer :

I got it this time. Can they be checked out while still mounted or do I have to take it off to check it out completely?

James W :

Only st you can do with it mouncted is LISTEN for the click and see i it has 12V when the ignition switch is on

James W :

ll else musbe tested with it in your hand

James W :

If there is ANY gum and varnish, you must clean the carb

James W :

I did not send you my carb info, did I ??

Customer :

When you say yhe "ignition switch on" are you referring to being turned all the way to crank or just to the first position on the switch?

Customer :

No. I did not get carb info

James W :

1st Position in running not starting position

James W :

Here comes a long carb page

James W :

Small engines are pretty simple systems (in theory).

In order to work your engine needs these things

  • Proper compression
  • Proper Gas / Air Mixture with good quality fuel.
  • Proper spark
  • Spark at correct time
  • Proper Lubrication (not required to start and run, but required for it to run very long).

I would check your compression, which must be at least 90PSI, and 110 is desireable.

If the compression tests good with a meter,

I expect you have either a fuel Quality or fuel delivery problem.

But first, we need to know it has spark.

Even if yo got it to start and it died, try to start the unit one more time,

Take the spark plug out, reattach the plug to wire to it and ground it to a head bolt. (When you had it out, was it wet or dry)?

If it is dry, we are 99% sure we are on the right track, but we still need to know if you have spark.

Turn unit on and either pull rope or engage electric starter. Look for a bright blue spark and see if you hear it. If it has spark, put a teaspoon of gasoline in the plug hole and reinstall the spark plug.

If the unit tries to start, but only runs until the gas you put in is gone then we need to look at cleaning the carburetor (especially if the plug was dry when you took it out).

Some of these engines have a tendency to sheer flywheel keys. If this happens, you may have no spark, or it may spark at the wrong time because the flywheel has spun on the crankshaft. Eventually, you may want to check this.

You may get lucky and it may start and run. If so, let it. It may "clear its throat" or you may get some work done right now.

Most likely you have a fuel delivery or fuel quality problem.

As engines sit or get older, fuel that is left in the carburetor can turn to gum and varnish and cause this and other problems.

Also, any gasoline that was left in a gas can for a period of more than 30 days must be discarded because it also has begun to turn to varnish.

Today's gasolines contain MTBE and alcohol. (Ethanol) They turn to "Junk and garbage" very quickly. Alcohol absorbs water. And they call it "Oxygenated fuels! It is the oxygen (and the water) that breaks down the organic compounds in the fuel and turns the gas to "Garbage" (Gum and varnish) The fuels we had just a few years ago had no alcohol in it and would store for longer periods of time before going stale.

Fuel stabilizers do almost nothing to prevent the fuel from going bad with the changes in today's fuels. The whole point of a fuel stabilizer is to form an oily film on the surface of stored gasoline whether in the tank or in a gas can. The idea was to keep oxygen away from the gasoline to prevent breakdown. Since the fuel is already oxygenated, the fuel stabilizer concept is null and void. These fuels start to degrade immediately upon the addition of the ethanol.

Do not buy gas from the "Discount" Stations. The discount stations get a reduced price on gas because they may be buying fuel that is nearly 30 days old already. You may be getting fuel that's nearly stale right from the pump when buying from a discount station. Purchase your fuel from the well-known stations such as Shell, BP, Sonoco, Phillips 66 etc.

More than 70% of all of our repairs in our small engine repair business are due to these same issues. You most likely have dirt, gum, varnish...etc in your carburetor plugging up the small passageways and jets in the carburetor.

The carburetor will need to be cleaned and overhauled as well as the rest of the fuel system.

  • If you plan to do the work yourself, take pictures with your digital camera or at least make a drawing of where all the linkages, gaskets, and component parts go. Correct reassembly is critical.
  • Remove the carburetor from the engine.
  • Remove all of the non-metallic parts since the carburetor cleaner will cause them to be disfigured decompose and plug the carburetor as time goes on.
  • Clean all parts with carburetor cleaner.
  • Blow out all the small holes and passageways with compressed air.
  • Use a tiny stiff wire such as is found on the twist tie on a loaf of bread or on a garbage bag to open all tiny passageways found in the carburetor such as in the screw, nut, or jet holding the bowl of the carburetor on (if it has a bowl). Make sure to look for tiny holes in the bottom and side threads of the bowl nut or nozzle a make sure they are clear with the wire.
  • Wash the carburetor cleaner off of the metal parts by washing them in warm, soapy water then rinsing with clean water.
  • Dry all carburetor parts by blowing it off with compressed air.
  • Make sure that all the passageways are blown dry before reassembling (you do not want water back in the carburetor).
  • Reassemble the carburetor using a NEW carburetor rebuild kit.
  • NOTE: DO NOT TRY TO REASSEMBLE WITHOUT USING A COMPLETE CARBURETOR KIT! You will just end up having to do the job again.
  • Find the Model, type and serial or code numbers off of the engine and take them to your local dealer to get the carburetor repair kit.
  • ALWAYS clean the fuel tank and replace the fuel line when doing this repair or you may have to do it all over again. The inside of the fuel line disintegrates over time and these small pieces of rubber will plug up the carburetor too. Dirt and water from a dirty fuel tank will also plug up the carburetor. If this happens, you will be starting over again from the top.

In an Emergency such as a blizzard where you cannot get out to buy a carburetor kit until the plows come through, or during an emergency power outage and you need a generator running even if it runs poorly, you might try the following if your carburetor is the type that has a bowl. Sometimes this procedure works:

While the carburetor is still mounted to the engine:

  • Pinch the fuel line with a pair of vice grips to stop the fuel from going to the carburetor.
  • Remove the bowl nut (or nozzle from the bottom of the carburetor and let the fuel drain from the bowl.
  • Carefully remove the bowl from the carburetor without letting the needle and seat and float fall out of position (if it does, no big deal, but you will have to reassemble it, which is harder with the carburetor on the unit).
  • Dump all of the Gunk out of the bowl and put the bowl back into position.
  • Use a tiny stiff wire such as is found on the twist tie on a loaf of bread or on a garbage bag to open all tiny holes in the screw, bowl nut, or nozzle that was holding the bowl of the carburetor on (if it has a bowl). Make sure to look for tiny holes in the bottom and side threads of the bowl nut or nozzle a make sure they are clear with the wire.
  • Reassemble and see if you got lucky.

You may be able to finish the job at hand then clean and overhaul the carburetor correctly when you have more time and a new carburetor overhaul kit.

If you don't feel comfortable with these kinds of repairs, or if the carburetor still doesn't work correctly after your attempt, I would suggest sending it to a profession repair shop with a reputation for having friendly, knowledgeable, experienced service technicians. It would be best to take it to someone who has an "Ultra-sonic" cleaning machine. This machine uses a very mild carburetor cleaner in concert with ultrasonic vibrations to get the very small passageways clean. This method is very effective even when traditional methods fail.

There is a New Product that you can try.

http://www.b3cfuelsolutions.com/html/mib.html

It si designed to help clean the carburetor without damaging the diaphrams and rubber parts like regular carburetor cleaner. Click on this site and it will tell you all about it. http://www.b3cfuelsolutions.com/html/mib.html

The mechanic in a bottle is NOT a conventional carburetor cleaner.

It actually breaks down the varnish into it molecular components and it completely dissolves. It DOE NOT clog up the jets as conventional carburetor cleaners do. Conventional carb cleaners just loosen the varnish and the varnish particles will go into the jets and filters and clog them up.... usually causing much more problems that was originally there. The conventional carb cleaners also will loosen the "GUMK" that has formed in the gas tanks and cause all of that gunk to go through the carburetor as well.

The Mechanic in a BOTTLE is a completely revolutionary product that will in many case alleviate the need to tear the carburetor down and rebuilt it..... unless there is mechanical wear and tear that would require that parts be replaced.

In addition, the special formula actually is designed to soften and restor the rubber parts in the carburetor such as the needle and seats and gaskets.

Mechanic in a bottle is NOT a cure-all but it can help customer get going in many cases without them having to tear the carburetor apart. If the customer is NOT mechanically inclined, it might save them a trip to the repair shop.

Yes I was very skeptical about this product when I first was introduced to it, but the Distributor demonstrated it and we have tried it on many occasions with terrific results.

Otherwise you will have to clean and rebuild the carburetor.

Please feel free to ask follow-up questions so that we can always arrive at the correct solution. We want you to be 100% satisfied.

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Technician: James W, Small Engine Troubleshooting Expert replied 6 years ago

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James W, Small Engine Troubleshooting Expert
Category: Small Engine
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Experience: 7 years as Mechanic & Parts Manager for Brother who has Owned Lawn & Garden Repair shop for 35 years

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