HELP PLEASE - Engine hard to start and surging/backfiring

jasonzns · Oct 16, 2018

I have a Husqvarna 5424Z with a Briggs model 44S877-0014G1 that is only 3 years old.

For the past 3 months I have been dealing with hard starts and surging/backfiring/dying. I have to spray starting fluid to get it started and once I have it running I can usually run the blade engaged for about 20 minutes before it starts missing and RPM's are no longer stable. If I disengage the blade and lower the throttle for about 5-10 minutes it will stop misfiring and run for maybe another 5-10 minutes before the problem returns.

Now for the troubleshooting steps I have taken

1. replaced spark plugs and gaped to spec
2. replaced magnetos and gaped to spec
3. replaced vacuum hoses (there was a crack in the hose from the valve cover)
4. replaced air filter
5. replaced carburetor with new
6. replaced fuel pump
6. sprayed carb cleaner near all hoses checking for vacuum leak (nothing)
7. adjusted the valves to specs (slightly off)
8. removed gas cap and placed a sock over

Honestly to me it feels like its either starving for fuel or flooded but there is no smoke. Must be fuel related as it wont start without starting fluid

What have I missed? I am desperate to cut my lawn..

Darryl G · Oct 16, 2018

What about the fuel tank and fuel lines? Have you drained and cleaned the tank? The outlet could be partially plugged. May as well replace the lines while you're at it.

jasonzns · Oct 18, 2018

I have not cleaned the tank or the hoses from the tank. I will give this a try..

Also what about the gas cap? I haven't replaced but did attempt to remove it completely by putting a sock over it with a rubber band.

Do you agree that its fuel starvation?

Darryl G · Oct 18, 2018

Cap/venting issue usually shows up after running for a while so I don't think that's it.

I'm not one of the experts on this site - I'm just a landscaper - in my experience surging is usually a fuel supply or air infiltration issue.

sgkent · Oct 19, 2018

guessing this is carb and not FI. My best guess is fuel starvation (dirty filter, failing fuel pump, or tank vent plugged) or critters have built nests around the motor and it is getting too hot. The engine may be slowly going lean as the fuel level in the bowl drops then it runs hotter. You slow the engine down and the bowl refills so it runs better.

Walt 2002 · Oct 19, 2018

Boy, you might as well bought a new engine. Should be easy enough to tell if fuel starvation or flooding. Add some choke manually to see. IF you can't figure out how to do that, remove the air cleaner and use your hand over air horn. People are always replacing B&S CDI units which are pretty trouble free. Much more likely is the "Kill Wire" harness on these. To test, unplug each Kill Wire at the base of the CDI. Given the symptoms you mention, first thing I would do is try some SeaFoam per instructions on container. Water in fuel is another possibility.

Walt Conner

jasonzns said:
I have a Husqvarna 5424Z with a Briggs model 44S877-0014G1 that is only 3 years old.

For the past 3 months I have been dealing with hard starts and surging/backfiring/dying. I have to spray starting fluid to get it started and once I have it running I can usually run the blade engaged for about 20 minutes before it starts missing and RPM's are no longer stable. If I disengage the blade and lower the throttle for about 5-10 minutes it will stop misfiring and run for maybe another 5-10 minutes before the problem returns.

Now for the troubleshooting steps I have taken

1. replaced spark plugs and gaped to spec
2. replaced magnetos and gaped to spec
3. replaced vacuum hoses (there was a crack in the hose from the valve cover)
4. replaced air filter
5. replaced carburetor with new
6. replaced fuel pump
6. sprayed carb cleaner near all hoses checking for vacuum leak (nothing)
7. adjusted the valves to specs (slightly off)
8. removed gas cap and placed a sock over

Honestly to me it feels like its either starving for fuel or flooded but there is no smoke. Must be fuel related as it wont start without starting fluid

What have I missed? I am desperate to cut my lawn..

MowLife · Oct 19, 2018

I’d start with a compression test...if all good more than likely fuel starvation.

Boobala · Oct 19, 2018

Pull the fuel line off the pump to carburetor, see if it's pumping gas, if yes, it would indicate carb or possible ignition issue, if not, then fuel flow from tank to the pump may be blocked, if there was trash in the tank or lines after you installed the new carb, then you may have pulled it into the pump and carb .......... check the plug(s) for firing..........

HELP PLEASE - Engine hard to start and surging/backfiring

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jasonzns

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