Dolmar 421problem

[woodbutcher56]

Close inspection NOT cluster !!! Smart phone my a*!#

 

[sugarbush]

what the dealer said is interesting, did he say why the intank fuel line?

 

[woodbutcher56]

The way I understand it the B&S rep visited my dealer(he's the guy that hooked my dealer up with Dolmar 10 years ago) my dealer quized the rep the rep called another , in his words huge dealer that sells over 200 saws a year, that dealer said they had 1 saw a 421 come in with the same problem and the culprit was the in tank fuel line .

 

[CoreyB]

Did anyone mention some earlier models needed an oring on the fuel line to keep them from popping off.

Edit! Sorry my phone just updated I see this has been adressed.

 

[Chris-PA]

To make the idle speed rise you have to either change the L mixture to closer to the the max idle speed setting (which implies it must have started somewhere else), or increase the idle air flow. I suppose something that changes the ignition timing could change the idle speed too, but that seems like a long shot. Starting there, if in fact the H operation is unchanged, then you have to come up with things that only effect L.

The first thing I'd do is see where the L mixture is set - how far from max best idle is it and on which side? Then I'd look at the throttle linkage and operation of the carb throttle shaft. Last, I'd look at fuel lines - but I'm not sure how a fuel line problem effects idle when the fuel flow rate is low and does not effect higher fuel flow rates.

 

[woodbutcher56]

To make the idle speed rise you have to either change the L mixture to closer to the the max idle speed setting (which implies it must have started somewhere else), or increase the idle air flow. I suppose something that changes the ignition timing could change the idle speed too, but that seems like a long shot. Starting there, if in fact the H operation is unchanged, then you have to come up with things that only effect L.

The first thing I'd do is see where the L mixture is set - how far from max best idle is it and on which side? Then I'd look at the throttle linkage and operation of the carb throttle shaft. Last, I'd look at fuel lines - but I'm not sure how a fuel line problem effects idle when the fuel flow rate is low and does not effect higher fuel flow rates.

I appreciate your help. I seriously doubt the fuel line will cure the problem. They base that on the fact that fuel has always been 1/2 tank or less. I believe the fuel level is there because that's how much the saw used to reach the temperature where the problem starts. In the thread from 'gearjunky' he stated that if he pushed the primer bulb during high idle the saw would idle properly ,briefly.

 

[woodbutcher56]

Ambient air temp the first occurrence was warmer than the second occurrence and the first time the saw had nearly 1/2 tank of fuel the second time a little over 1/4. Colder temp longer run time to reach the same temp. Coincidence maybe??? The confusing part is I ran a whole tank of gas through it with no issues in between the two occurrences?? If the saw had at I'd swear the problem was electronic in nature.

 

[woodbutcher56]

Both times the problem went away after the saw sat and cooled off!

 

[CoreyB]

Both times the problem went away after the saw sat and cooled off!

Hmm coils are notorious for causing trouble while hot and being fine cool.

 

[woodbutcher56]

I thought of that , but if the coil was breaking down wouldn't the saw be rich?

 

[Sepia]

Just a thought, but possible that the impulse line is leaking slightly after saw heats up, and is not providing enough signal/pulse to the diaphram at idle to feed the carb, but does have a strong enough pulse at WOT?

 

[CoreyB]

I thought of that , but if the coil was breaking down wouldn't the saw be rich?

I have seen coils do weird things that make little sense and can be hard to put a finger on.

 

[MountainHigh]

might be the vent valve - hot saw with sticky valve could feel like vapour lock.

check this thread out . . .
http://www.arboristsite.com/community/threads/dolmar-421-help.291731/

 

[woodbutcher56]

Just spoke with the dealer on the phone he has not verified that there is a problem with the fuel line. He said they have to separate the tank from the saw to replace the line and didn't want to leave my saw in pieces on the bench until the part comes in. They are going off of the previous experience from the other dealer. So at this point it's just speculation.

 

[woodbutcher56]

Just a thought, but possible that the impulse line is leaking slightly after saw heats up, and is not providing enough signal/pulse to the diaphram at idle to feed the carb, but does have a strong enough pulse at WOT?

This makes more sense to me than the bad fuel line .

 

[woodbutcher56]

Just have to wait and see! Dealer said it would be the middle of next week for the part.

 

[sugarbush]

sounds like there has to be an air leak for your saw to idle so fast that the chain runs. your dealer can check the fuel system for an air leak by pulling the line out of the tank and pressurize it. but if he cant do that just remove the in tank line and replace with a piece of fuel line. his warehouse may not have that line in stock anyway, mine don't, its on back order. if your saw starts to idle fast after running about a half tank of fuel and then will run ok after it cools down and you didn't add more fuel i don't think its your fuel line. i wonder if your dealer done a proper leak down test because your saw symptom is an air leak, the fuel line is what i would have checked first then the engine, which would have included the impulse.

 

[woodbutcher56]

sounds like there has to be an air leak for your saw to idle so fast that the chain runs. your dealer can check the fuel system for an air leak by pulling the line out of the tank and pressurize it. but if he cant do that just remove the in tank line and replace with a piece of fuel line. his warehouse may not have that line in stock anyway, mine don't, its on back order. if your saw starts to idle fast after running about a half tank of fuel and then will run ok after it cools down and you didn't add more fuel i don't think its your fuel line. i wonder if your dealer done a proper leak down test because your saw symptom is an air leak, the fuel line is what i would have checked first then the engine, which would have included the impulse.

I totally agree! I wonder too about the leak test. No way for me to know. He said he did and cleaned the carb and retuned. The saw has started and idled properly after cooling down each time with no added fuel. I'm at the mercy of the dealer I guess.
Thanks for your input ,greatly appreciated.
Would I be out of line to ask for documentation of everything the dealer has done ? Fordf150 said they would be glad to check it out if the locals can't figure it out. I would just have to ship the saw.

 

[sugarbush]

Not sure how to tell you to approach this problem with your dealer unless you have a good relationship with him. But for him to just guess what's wrong and replacing that line is a little foolish. If that doesn't work, then what? If you do have a good relationship with him, somehow make a suggestion to pressurize that fuel line to check for an air leak, and if there isn't one, I don't see any reason for replacing it. I've sold quite a few 421/EA 4300's and have never had a leak in a fuel line. (I have had a few fuel lines slide off in the cold weather and was an easy fix.) As far as documentation, I don't think that will do you much good. I think Fordf150 is in Ohio so I don't think it would cost too much to ship it to him and back. Makita may just pay for your shipping fees if that's what it takes to get your saw fixed. Keep us posted on this in case I'm wrong about an air leak. LOL!

 

[7sleeper]

Just simple speculation, but maybe the fuel line has a pinhole in the "middle" and as soon as the fuel drops below a certain level the problems evolve.

So it is too bad you didn't refill the saw when the problems started to see if they went away when the tank was full again.

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