Help with 8HP L head 190412 runs 1 min and stalls

First off hi all. newb here. I like to think I'm a fair backyard mechanic. Like most I suspect and need for help led me here.

I have a 8HP L head 190412 runs 1 min and stalls. It is on a 1988 Homelite Generator.

I have been chasing this problem for a while. I have:

-replaced fuel lines and inline filter.
-replaced carb (med flo-jet)
-replaced plug
-put on a used coil

I have homemade inline spark tester that shows spark. I have run with out fuel cap. all no change.
I have pulled muffler and soaked exhaust valve with LMT, as well as putting in plug hole.

I have been told low oil shut off could be suspect, but I do not see that this engine has a low shut off sensor.

I have owned since new, and other than being lazy and storing with gas, I do not know of any issues. It has always run fine until this.

I am hoping someone can shed some light. All replies are appreciated. Thanks for lookin.

Thanks,
Jim

First thing first.
Run the engine with the spark tester fitted and watch what happens.
spark stops before the engine does = ignition problem.
Keeps on flashing all the way to the bitter end = fuel problem.

Sounds like a fuel problem. The engine is running on what's in the bowl. When it stops the bowl then fills back up slowly. Then the process is repeated.

A bad bad coil will go out in a minute but usually they run for 10 minutes or so.


Could be where the line goes in the tank is all gummed up I have seen that before.

Take the fuel line off the carb and put it in a quart jar. See how long it takes to fill it up ~!~!

assuming the gas is new and not old, because old gas will work that way, is there a pump between the tank and carb? Follow the line from the tank.

Sometimes as a quick test I will disconnect the fuel line at the filter, and give a quick bust or two of compressed air through the line back to the tank. That will clear any blockage in the fuel line. If it works, but only for a little while, I would consider that there may be debris in the tank, or in the fuel shutoff valve, if it's the kind attached under the tank.

I would replace the fuel pump, fuel lines and vacuum line because those go bad too. Make sure that the fuel valve under the tank is open and not in a closed position if your motor has one. Lots of people forget about that valve.

Most likely if the fuel pump is original and not cracked you can get a rebuild kit. If the fuel pump has been replaced with the later style or it is cracked then it may be a different style because the original fuel pump is no longer available - in fact on a 192402 8 HP engine I just spent a month looking for either a new old stock one or a rebuildable core.

Thanks all for the replies.

I ended up taking to shop. They claimed new carb required clean and adjust. Claiming this was common with aftermarket carb. I noted a new fuel line and filter, installed but not mentioned. They also mentioned not to used gas that had ethanol.

Thank you all for your replies and assistance offered here.

Jim