Mac 10-10 spark “fuel” and compression but won’t start.

[MelonBoi1]

I just rebuilt my mac 10-10 and it has sufficient compression to run, it is above 125 psi and spark is good it is bright blue, and when I put fuel down the carbs throat it starts and then dies. The carb is freshly rebuilt (by leons chainsaw parts and repair) and I am sure we can get this situated because already the good news is that it will fire, it just won't stay running. So I put fuel in the tank and it won't start. Check the fuel line for blockage and it flows just fine. In case the carburetor was just dry and needed to be primed I kept trying to put 2 cycle mix down the carburetors throat and that worked but like I said, it won't stay running, I did that a couple more times and then when I did it again it just wouldn't start. I tried unflooding the engine but that didn't help, I will try again tomorrow but I need answers, I have worked so hard on this saw and I want to try everything before just flushing it all down the drain.

[rusticretreater]

See if this video helps you out.
McCulloch MAC 10-10 Automatic Chainsaw: Get Running Again
https://www.youtube.com/watch?v=bzWvGvlW98U

[MelonBoi1]

I don't need a video, I need someone to help me.

[doc henderson]

so, you are not getting fuel via the "carbonator" (carburetor).  It works when dumped in and not when trying to aspirate from the carb.  fuel is the problem.  

[doc henderson]

see if the folks that rebuilt the carb can look at it for you, if you cannot find the prob.  starts at the tank filter all the way to the carb venturi.  I had one that ran for the first half a tank then would die and not restart.  My Stihl mechanic told me a common prob. is a formed fuel line that had a bend, would get a crack and at half a tank, start sucking air.  he fixed it in 10 minutes.

[doc henderson]

I am not familiar with the mac 10.  will it run on choke, or does it have a primer bulb?  I had two Mac saws but that has been over 30 years ago.  one homelite and nothing but Stihl since.

[beenthere]

Sounds like an air leak in a fuel hose, or something on that order (from listening to others talk about this symptom). 

[chet]

I don't need a video, I need someone to help me.

Just by the fact that you had a shop go through the carb, rather than doing it yourself.  I'm guessing, maybe just maybe, you might have found something to help you diagnose the problem with your saw,  watching the video.  Rude responses such as yours above are not needed or tolerated here.

[Old Greenhorn]

[MelonBoi1]

I don't need a video, I need someone to help me.

Just by the fact that you had a shop go through the carb, rather than doing it yourself.  I'm guessing, maybe just maybe, you might have found something to help you diagnose the problem with your saw,  watching the video.  Rude responses such as yours above are not needed or tolerated here.

I am sorry if that came across as rude for that was not my intent, I am just frustrated that I put a lot of effort into this thing just for it not to run. There is no primer on it and I went through the carburetor myself too and all works fine, I checked the line and it is also fine and fuel flowed through it just as it should. Though When I did take the carb apart I did notice that it was bone dry, as if it wasn't getting fuel to it and that basically confirmed that it wasn't getting fuel to the carb to get into the engine. I suspect it is something with the way it sucks the fuel with crankcase pressure. But I am not sure.

[chet]

Not familiar with that saw, But assuming it doesn't have an impulse line. The first thing to then check, is when you installed the carb, is the carb to intake gasket on correctly. There should be a single small hole on one side of the gasket. That hole must line up with the hole in the intake.  If you flipped that gasket you are blocking the crankcase impulse.

[doc henderson]

they can be tricky devils.  If you take it to the shop that did the carb, they might have a look.  they do not want anyone thinking the carb did not work after a rebuild, but they may charge you a fee, if the problem is not the carb.  there are so many factors, but at least we know it is not getting fuel to the combustion chamber and you have a place to start.  this is the most common problem diagnostically in my opinion and there should be a fix, not a wasted toss "it in the can" solution.

[MelonBoi1]

they can be tricky devils.  If you take it to the shop that did the carb, they might have a look.  they do not want anyone thinking the carb did not work after a rebuild, but they may charge you a fee, if the problem is not the carb.  there are so many factors, but at least we know it is not getting fuel to the combustion chamber and you have a place to start.  this is the most common problem diagnostically in my opinion and there should be a fix, not a wasted toss "it in the can" solution.

Just to clarify I did not take it to a specific shop I bought it as a rebuilt carburetor from Leon's chainsaw parts and repair.

[thecfarm]

Just so you know about the you tube help.
My stepson can watch youtube and change motors. I entered his life in his mid 20's. He had a family and I was not much help showing him how to turn wrenches. His Father was not around to show him anything.
Now he can watch youtube and work on his vehicles.

[Al_Smith]

A common problem with the 10 series McCullochs is the fuel line inside the tank develop a small slit in them which will stop them from sucking fuel .Unless that fuel line has been replaced it might be very old and prone to breakage .Try filling the tank clear up to the top if you haven't already .

[DHansen]

Is the needle stuck in the seat from the carb sitting in storage or on the shelf?  Is the pulse circuit clear at the base gasket and to the block?  The pulse circuit is needed for fuel to be pumped, but the needle is a location that stops the flow into the carburetor.  Just two things that I would check if I was working on this 10-10. 

[MelonBoi1]

A common problem with the 10 series McCullochs is the fuel line inside the tank develop a small slit in them which will stop them from sucking fuel .Unless that fuel line has been replaced it might be very old and prone to breakage .Try filling the tank clear up to the top if you haven't already

A common problem with the 10 series McCullochs is the fuel line inside the tank develop a small slit in them which will stop them from sucking fuel .Unless that fuel line has been replaced it might be very old and prone to breakage .Try filling the tank clear up to the top if you haven't already .

The line is new and flexible.

The line is new and flexible

[Hilltop366]

Old saw, If everything else checks out it could be the crank seals.

[MelonBoi1]

Is the needle stuck in the seat from the carb sitting in storage or on the shelf?  Is the pulse circuit clear at the base gasket and to the block?  The pulse circuit is needed for fuel to be pumped, but the needle is a location that stops the flow into the carburetor.  Just two things that I would check if I was working on this 10-10.

I made sure the needle was unstuck, I do plan to do a full inspection on those pulse circuits.

[MelonBoi1]

Old saw, If everything else checks out it could be the crank seals.

The saw is restored by me, new rings piston, seals everything.

[Al_Smith]

As usual attempting to trouble shoot a chainsaw over the internet is like herding cats .One last thing then I'm done .If I am correct the carb has a hole in it for the impuse which comes from the cylinder via a hole in the intake .It should have a  gasket with a hole in it for the impulse and if it's installed bottom side up it will block the impulse .No impulse no putt putt.

[chet]

Al you weren't paying attention, we covered that. 

[DHansen]

You could try this to help with diagnosis.  Get a clear bottle Put 2 stroke fuel in it about half full.  Mark fuel level with a sharpie.  Use a clear hose from the bottle to the carb inlet fitting.  Remove the spark plug.  Have ignition shut off so there is no spark.  Pull the engine over a few times and see if it pulls fuel through the clear hose.  This would determine if the saw is capable of pumping fuel.

[doc henderson]

OK, I misunderstood.  so, are they online?  If it checks out bad, you may want to let them know to see if they can make it up to you.

[lurk]

Didn't see any mention of pressure and vac testing the crankcase after the rebuild, I read the seals were changed but that doesn't mean they're not leaking. Obviously a leak would cause a very weak or non excitant pulse to the fuel pump. 

Also if you used sealant on any of the gaskets make sure it hasn't plugged the pulse channel.   And as mentioned many times, the inlet gaskets and insulator need to be the correct ones and fitted correctly. 

[MelonBoi1]

You could try this to help with diagnosis.  Get a clear bottle Put 2 stroke fuel in it about half full.  Mark fuel level with a sharpie.  Use a clear hose from the bottle to the carb inlet fitting.  Remove the spark plug.  Have ignition shut off so there is no spark.  Pull the engine over a few times and see if it pulls fuel through the clear hose.  This would determine if the saw is capable of pumping fuel.

I would do that but the fuel line is molded and I cannot put clear line on it.

[MelonBoi1]

Didn't see any mention of pressure and vac testing the crankcase after the rebuild, I read the seals were changed but that doesn't mean they're not leaking. Obviously a leak would cause a very weak or non excitant pulse to the fuel pump. 

Also if you used sealant on any of the gaskets make sure it hasn't plugged the pulse channel.  And as mentioned many times, the inlet gaskets and insulator need to be the correct ones and fitted correctly. 

Yes but the problem is I don't have a pressure test thing for that and I don't really have a way to cover up the cylinder ports with anything. I think I should focus on that right now, because I thing one of the seals I might have installed wrong.

[beenthere]

Melonboi
You have your work cut out for you, and we wish you the best finding where that problem lies. Good luck, and hope you take us along on the hunt. We are interested.

[doc henderson]

Maybe you understood this, but I think DHanson was suggesting a dry clear water bottle of fuel with some clear tube the same size as the fuel barb on the carb.  with switch off and plug removed so it is easy to crank but will not fire, see if the carb is working to pull fuel.  this is a test that you can do with simple materials.

[Al_Smith]

Al you weren't paying attention, we covered that. 

Well for Pete's sakes we've collectively covered just about anything that could be wrong with the danged thing .Of course there's the "new" carb which doesn't say it's a good one .I give up it's just got saw gremlins uncurable evidently .Maybe I'm just lucky,i have several 10 series Mccullochs from early right hand start 10-10's up to nearly the last model ever made plus including an 805 .They all run and quite well considering how old they are .Like I've touted --'tain't rocket science .

[MelonBoi1]

Maybe you understood this, but I think DHanson was suggesting a dry clear water bottle of fuel with some clear tube the same size as the fuel barb on the carb.  with switch off and plug removed so it is easy to crank but will not fire, see if the carb is working to pull fuel.  this is a test that you can do with simple materials.

I don't think it will help because we already went over the fact that when I took the carb apart after it wouldn't start, it was bone dry.

[doc henderson]

Okeedoke!

[DHansen]

Yes, your carb as stated was bone dry.  So now we try and figure out why.  Its a simple fuel system.  By doing the test I suggested you eliminate part of the fuel system and you determine if the pump is capable of pumping fuel.   If it is not pumping, either the carb is put together incorrectly, or the pulse line is obstructed.    I can link to a vacuum pressure test I did a while back.  Not hard to do.  

[chet]

Have you pulled the carb and double checked that the gasket isn't flipped yet? I would not proceed any further until you verify that!

[MelonBoi1]

I pulled it apart so yeah.

[doc henderson]

guys if the carb is off can you/should you hear or feel pressure/air from the port to the impulse channel with the carb off and pulling it over?  I have never tried it.  Melonboi, you did not want a video and asked for help.  It may just be your communication style, but all the suggestions seem to be dismissed.  It sounds like the saw has a minor hard to figure problem that can be fixed.  we are trying to isolate and diagnose the problem.  It has a fuel problem.  we are trying to narrow that down, so you are not shooting in the dark, and only have to check a few things.  We are happy to try and help you get that thing running.  

[Al_Smith]

In general conversation concerning carbs if you place the spacer gasket for the main disphragm out of order in assembly it will not pump .Carb out it's spacer then diaphragm then cover .I once had a brain fart and assembled one out of order but it was a Stihl not a McCulloch .That one about drove me bonkers .Got mad and punished the saw by parking  it on the shelf for a couple of months .After which with cooler heads prevailing the answer was as obvious as the south end of a north bound goat .Humbled by a carb ,things happen  

[chet]

I pulled it apart so yeah

So the rather more than obvious question is, what did you find? 

[MelonBoi1]

guys if the carb is off can you/should you hear or feel pressure/air from the port to the impulse channel with the carb off and pulling it over?  I have never tried it.  Melonboi, you did not want a video and asked for help.  It may just be your communication style, but all the suggestions seem to be dismissed.  It sounds like the saw has a minor hard to figure problem that can be fixed.  we are trying to isolate and diagnose the problem.  It has a fuel problem.  we are trying to narrow that down, so you are not shooting in the dark, and only have to check a few things.  We are happy to try and help you get that thing running. 

I am not dismissing anything 

[MelonBoi1]

I pulled it apart so yeah

So the rather more than obvious question is, what did you find?

Nothing worth noting besides the fact that it was bone dry, I can always use the other carb that I rebuilt but I don't think it will make a difference.

[MelonBoi1]

And people keep mentioning this but I know you can put the gasket on the wrong way and stuff. Every time I put it back together I always put it on the right way You can't mess it up because of the way it is designed.

[beenthere]

As "jack of all trades", you will find the problem and have it up and running in no time. Let us know when you find it. 

[Hilltop366]

So if the carb is assembled correctly and everything in there moves freely, the needle valve leaver is set right, the diaphragm is installed correctly on the leaver and the flaps on the pump side are not stuck to the carb, the fuel line and filter are good and the carb is still dry it only leaves the crankcase pulse to be faulty for the carb to be dry so with the carb gasket on correctly it leaves:

1) the pulse hole is blocked in the top piece or crank case, with carb removed put some heavy oil in it to see if the oil moves when pulling saw over. 

2) a leak in the crankcase or seals or in between the crankcase and the rear handle/ fuel tank assembly.

A pressure/vac tester tool will answer that, could improvise with a bicycle pump with a gauge so not to over pressurize it and a spark plug with centre removed and solder a metal tire valve to it.

[MelonBoi1]

As "jack of all trades", you will find the problem and have it up and running in no time. Let us know when you find it. 

Yeah well the reason I want help is because the Mac 10-10 is in my opinion a poorly designed saw and I wouldn't just make a thread like this just to document what is going on. The point is for me to ask for help.

[MelonBoi1]

So if the carb is assembled correctly and everything in there moves freely, the needle valve leaver is set right, the diaphragm is installed correctly on the leaver and the flaps on the pump side are not stuck to the carb, the fuel line and filter are good and the carb is still dry it only leaves the crankcase pulse to be faulty for the carb to be dry so with the carb gasket on correctly it leaves:

1) the pulse hole is blocked in the top piece or crank case, with carb removed put some heavy oil in it to see if the oil moves when pulling saw over.

2) a leak in the crankcase or seals or in between the crankcase and the rear handle/ fuel tank assembly.

A pressure/vac tester tool will answer that, could improvise with a bicycle pump with a gauge so not to over pressurize it and a spark plug with centre removed and solder a metal tire valve to it.

Yeah probably not. Too much DIY. I will look for a pressure test kit but I need to know how to use it on this.

[MelonBoi1]

Is there any part number or plate thing that I can use to cover up the ports for the pressure test? And I am not going to cut up a piece of metal I don't have the tools fot that.

[Hilltop366]

No metal needed, it is common to use a solid rubber gasket in-between the muffler/ carb and the saw body. Even a piece of inner tube (or doubled over) would do as you don't need much pressure, 7 or 8 psi would be enough.

Check out a couple of youtube vids for ideas.

Check the pulse hole to see if it plugged first, no special tools required.

[DHansen]

Just some added information about vacuum and pressure testing.  I would get a Mighty Vac gauge set up.  They work great for this test.  An old compression gauge fitting to screw into the spark plug hole works great.  An old inner tube cut to fit and block the exhaust port on the cylinder between the muffler and the block will seal the exhaust side.  You can put the rubber in and bolt the muffler back down.  On the intake, rubber from an inner tube will also work, but a small plastic block, metal or work to seal the rubber to the intake works better than bolting the carb back on.  But whatever works best for you or what you have around to seal it with. 

ADDED:  I found information saying not to apply too much pressure.  Seems that 5-7 PSI is the recommended pressure for pressure testing.    Also seems that most are also using 5-7" Hg vacuum for vacuum testing.

ADDED:  No more than 1" HG loss per minute and no more than 1 PSI loss per minute.  But I have seen several comments that a good saw will hold 7 Hg vacuum for 5 minutes and not lose any. 

[DHansen]

Photo of Mighty Vac gauge.  Compression fitting with core removed and vacuum hose connected to compression gauge fitting.  It sounds like you already have a compression tester, so use that fitting, but remove the valve core.  I bought my Mighty Vac used for $30.00 US.

[doc henderson]

great information gents!

[MelonBoi1]

Photo of Mighty Vac gauge.  Compression fitting with core removed and vacuum hose connected to compression gauge fitting.  It sounds like you already have a compression tester, so use that fitting, but remove the valve core.  I bought my Mighty Vac used for $30.00 US.

Interesting but I am not a compression tester expert. I need to get one without bending and cutting and fabricating my own system. I can make the sealing plates but I can't make some goofy jig for the compression tester.

[DHansen]

The valve core threads out of the compression tester adapter. Just like a valve core from a tire pressure stem.  The hose slides over the end nipple of the compression adapter.  Thread adapter into the spark plug hole on the cylinder head.   Don't even need to use a clamp on the hose.   No cutting or bending.  Unless you are talking about cutting the inner tube to size.  I am just trying to help you diagnose the issue with your saw.  No magic bullet, just tests that will help eliminate the possible causes.   Eliminate one thing at a time and move forward to pinpoint the cause.  You have already confirmed ignition and compression.  You have determined the carburetor is dry inside.  Your description suggests a lack of fuel flow.  So, either the saw is unable to pump due to a pulse issue or there is a carburetor problem.  Pick which one to trouble shoot first, then move forward.  Making it work is all up to you and your abilities.  You are adding additional troubleshooting skills to your talents and learn by trying.

[beenthere]

Take it to a chainsaw doc. 

Someone who will do the good suggestions provided here and then fix your saw. 

[Al_Smith]

I would not suggest a 10-10 Mac is a poorly designed saw .They made them or some variations of them over 25 years .I think that is a record for a chainsaw .That said they are "old school " but usually very dependable .About the only way to kill them  is to straight gas them .Now that said they refuse to run unless the carb is getting fuel .It's not magic,not rocket science just the cold hard fact .However there is a device to end all the drama called a battery saw .If the battery is charged they always start plus they are very quiet ,no hearing protection needed .I've got one myself ,tiny thing that it is . If I had enough batteries in about 3 hours I could drop an 18" oak I'd imagine .

[WLzM1A]

I don't need a video, I need someone to help me.

Good way to never get help

[MelonBoi1]

I don't need a video, I need someone to help me.

Good way to never get help

Your comments are unnecessary.

[Al_Smith]

Well this has gone on nearly a month  .People have tried to help but it's been replied "that has already been done " .I for one have ran out of ideas except evidently something has not been done as reported it had been . Perhaps it's time to find somebody who is knowledgable about old McCulloch saws .I'm rather busy myself .--good luck ---

[Old Greenhorn]

I don't need a video, I need someone to help me.

Good way to never get help

Your comments are unnecessary.

Well to be fair, you kind of asked for it.  Some very knowledgeable folks have offered you some terrific guidance here and from what I see you have not given clear feedback on what you've checked and how you checked it. So they mention it again in another form and you get snarky with them. In fact, some might say you have been pretty demanding for results, which frankly is a bit rude.
 Looking at your other posts I see that you only post here when you have a problem you can't figure out, but I don't see you sharing your knowledge to help others. That's not exactly cricket as they say. I'm just pointing this out in case you didn't notice it. This forum works both ways, it's not a 'fix my problem' platform, although it very often is.
 I wish you the best of luck with your saw, but I think you may be turning off the very folks that are trying to help you. Good Luck an I hope you work through it.

[WLzM1A]

I don't need a video, I need someone to help me.

Good way to never get help

Your comments are unnecessary.

Neither is your.....nevermind. Good luck to ya 

[MelonBoi1]

I don't need a video, I need someone to help me.

Good way to never get help

Your comments are unnecessary.

Neither is your.....nevermind. Good luck to ya

What are you trying to say? 

[chet]

What he was politely saying, is your attitude will get you no where on this forum. He, like myself and others have bowed out from trying to assist you.
You will not find a more willing group to help, so it would be wise of you to not squander that opportunity.

[WLzM1A]

I don't need a video, I need someone to help me.

Good way to never get help

Your comments are unnecessary.

Neither is your.....nevermind. Good luck to ya

What are you trying to say?

It's pretty clear what I'm saying

[WLzM1A]

What he was politely saying, is your attitude will get you no where on this forum. He, like myself and others have bowed out from trying to assist you.
You will not find a more willing group to help, so it would be wise of you to not squander that opportunity.

Amen Chet