Husqvarna 455 won't idle, if it does, dies on acceleration.

[dsell]

Another 455 on the bench and I hope it's the last. Here's what's been done:
1. New fuel line
2. New fuel filter
3. New fuel vent
4. New purge bulb
5. New purge lines
6. New tank grommets for the fuel tank lines.
7. Cleaned the carb in ultrasonic and rebuilt with new Walbro kit.
8. Tried a known good plug
9. Checked kill switch.
10. Checked spark, good, consistent.
11. Pulled the intake, cleaned, checked carefully for cracks.
12. Pulled the flywheel, clutch, and muffler, pressured to 7 lbs and held steady. Sprayed soapy water everywhere looking for leaks. It's tight as a drum.
13. Took the carb down again and pulled the welch plug. Ran through ultrasonic again with stronger soap solution.
14. Doesn't matter where the needles are set, limiters are gone, it does the same thing. Same as when it arrived.
15. Good compression, both sides of the piston and cylinder are fine.
16. Spark arrester is clear.
17. Flywheel key is fine, gap is fine on the coil.
18. Impulse line was tested when I had it pressured up.
19. Only thing left is the coil or replacing the carb, unless you guys tell me there's something else to service in the carb. I need to check Walbro and make certain I have the metering lever set correctly. Just seems to run out of gas. You always have to choke it after it dies and it takes several pulls choked to fire again.
20. Did I say I hate this series? This is the 2nd 455 I've worked on and they both suck.

 

[Dawnsman]

Another 455 on the bench and I hope it's the last. Here's what's been done:
1. New fuel line
2. New fuel filter
3. New fuel vent
4. New purge bulb
5. New purge lines
6. New tank grommets for the fuel tank lines.
7. Cleaned the carb in ultrasonic and rebuilt with new Walbro kit.
8. Tried a known good plug
9. Checked kill switch.
10. Checked spark, good, consistent.
11. Pulled the intake, cleaned, checked carefully for cracks.
12. Pulled the flywheel, clutch, and muffler, pressured to 7 lbs and held steady. Sprayed soapy water everywhere looking for leaks. It's tight as a drum.
13. Took the carb down again and pulled the welch plug. Ran through ultrasonic again with stronger soap solution.
14. Doesn't matter where the needles are set, limiters are gone, it does the same thing. Same as when it arrived.
15. Good compression, both sides of the piston and cylinder are fine.
16. Spark arrester is clear.
17. Flywheel key is fine, gap is fine on the coil.
18. Impulse line was tested when I had it pressured up.
19. Only thing left is the coil or replacing the carb, unless you guys tell me there's something else to service in the carb. I need to check Walbro and make certain I have the metering lever set correctly. Just seems to run out of gas. You always have to choke it after it dies and it takes several pulls choked to fire again.
20. Did I say I hate this series? This is the 2nd 455 I've worked on and they both suck.

That's odd mine just wanted to idle wfo lol I couldn't figure why till I found a super tiny spot that looked line a stupid mouse bit into the intake boot swapped it out still a bit faster at idle than I like but its running

 

[dsell]

You can see some white stuff under the blue tongue and laying in the filter area. I wonder if it has plugged the nozzle with that crap and the ultrasonic isn't getting it. The owner uses ethanol free fuel, but the previous owner may not have. I'd guess the current owner has ran it 5 years.

 

[dougand3]

I don't like that white flaky stuff. You may have tiny particles screwing up fuel flow. I'd try a new carb - AM clones are ~$15.

 

[Thommo]

You need to clean off that white stuff so the fuel pump valves can seal. It wont pump enough fuel the way it is

 

[dsell]

I pulled it apart again and took the welch plug out again. Carefully inspected all the holes, poked wires through, shined lights through and they all are clear that I can see. I checked to make certain the lever is set .060 inch under the carb body. Blew through everything again and put it back together. Same thing, choke it, pull it 7 times, it runs until it's out of fuel. That just made me think, I should but a gauge on the impulse line. Anyway, I pulled the plug and pulled it many times to check the spark and it never misses, bright blue with two different plugs.

 

[Thommo]

Are the flap valves on the fuel pump sitting flat so that they seal. On the top photo it looks like one is curled up a bit

 

[dsell]

Are the flap valves on the fuel pump sitting flat so that they seal. On the top photo it looks like one is curled up a bit

The photos were taken when I took it apart originally. I just wanted to show the white stuff that built up in the fuel pump. It has a new white/beige flavored pump valve now from a new OEM Walbro kit. There are two items left in the carb that I don't have repairs for, the nozzle and whatever the other brass plug has under it. I ordered a Chinese replacement carb last night.

 

[dsell]

I removed the impulse line and hooked it to my gauge. The saw started on the 2nd pull, I wasn't expecting that with no impulse line. So, I took it outside and it behaved exactly as it does with the impulse line attached. The gauge shows impulses, the high pulse is 2 to 3 psi. Either the fuel pump isn't pumping or the diaphragm isn't opening the inlet needle. The Chinese carb is due to arrive Saturday. 84-643-1 is a check valve and 86-583-1 is the nozzle check valve. I suspect one of them is the culprit or there is a blocked passage to them. Some of the parts in the diagram don't exist on this model. I guess they use the same drawing for several models and then zero out the bill of material for the items that don't apply. Notice 1, 17, and 22 are missing in the BOM.

 

[Brad2185]

Does your carb have a accelerator pump?


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[dsell]

Does your carb have a accelerator pump?


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I don't believe it does.

 

[Brad2185]

I don't believe it does.

I know those o-rings behind the pump tend to fail


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[dsell]

This is a Walbro WTA-29. What carb has the accelerator pump?

 

[dsell]

The new chinese carb arrived today. I put it on and the saw started, I left it on fast idle and it ran a while before it slowly died. Started it again and it wouldn't accelerate, low turned all the way out against the limiter. So, I pulled the new filter out of the tank and replaced it with a new Husqvarna filter. The saw started and accelerated. Top end wasn't there and occasionally it would fall on it's face when accelerating. Seemed to float down from high rpm like an air leak would do. Certainly not snappy or responsive like it should be. I wonder if the butterflies are timed correctly. So, took the new chinese carb off and put my rebuilt back on. Saw runs like a top, didn't even need to change the needle settings. The pisser of the new chinese filter being the culprit, I suspected it early on. I used a large syringe and disconnected the fuel line from the carb and sucked fuel easily into the syringe. Does anyone know if there is a spec for how much vacuum it should take to pull fuel through the filter? I'll try to do some testing with my mity-vac when I get some time. Maybe the stone is not porous enough to allow the weak fuel pump to pull the fuel through it. I swore off chinese pistons, cylinders, chains, air filters, ignition coils, fuel line, and switches long ago. Now I can add chinese fuel filters and carburetors to the list. The carburetor came with a new air filter and there's no way it will go on the saw. The true test will be to have the owner cut with it a day before i'm satisfied it's cured.

 

[dsell]

I tested the new bad chinese filter. My Mity-vac would only pull 20lbs of vacuum and no fuel flowed. The weird part, when I relieved the vacuum the fuel flowed for a while. This was repeatable. So, the longer the saw ran the worse the flow was due to the vacuum build up. After it would run out of fuel and die, the vacuum was relieved and the fuel filled the carb up again. I tested the old filter and I couldn't pull a vacuum and the fuel flowed fine. The most vacuum I could see on the gauge was to the Z in ZERO but it was very brief.

 

[Thommo]

Did you change the fuel hose with the filter. I have had trouble with chinese fuel and vacuum hose sucking in from being too thin in the wall, but have not struck a bad filter yet

 

[dsell]

The spiral hose is oem. I used the gray Homelite hose for the primer. I used the expensive oem tank grommets, oem tank vent, and Walbro brand carb kit. The hose I did the test with is the old oem hose.

 

[dsell]

There is plastic film behind the screen that caused the problem.