Re: was running fine-turned off and now will ot...
The Carburetor or the AIS(Air Induction System) maybe the culprit or if they are fine, then the engine valves are needed to be replaced. Generally backfire occurs due to faulty engine valves.
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Hi Timothy:
Old Dude wisdom..........
- Fire at the plugs and
- Fuel in the jugs
If everything else is OK it should run. Not necessarily well, but it should run.
What to do?
1) Check for hot blue spark at the plug electrodes
2) Check for fuel in the carb.
If you have spark, give it a shot of gas into the carb, and give it a try. If it doesn't start, backfires, or catches fire, you'll need to double check the timing and plug lead firing order.
check the carburetor. If you have a stiff diaphragm then it won't run. I have seen them that behave just like that. They will run fine, turn it off for a few minutes then they won't restart. WD40 isn't going to get it to run either, try a small amount of mixed gas right into the carb. It should run for a minute until the gas you put in runs out then die. If it doesn't run then you have a bigger problem
If the unit runs normally after it starts it is probably a defective coil that isnt changing timing relative to crank speed. It is running advanced even at slow speeds and that is the backfire. You could also have a slightly bent flywheel key. This is what sets the primary timing so it is always a good idea to check it when you have the engine cover off!
I know you mentioned the EGR valve has been replaced, but you may have a bad 'new' part. I know the car is electronic, but has anyone checked its ignition timing (timing belt been looked at, I know it only has 77k on it). Is the fuel pressure regulator OK and it vacumm supply?
I find my 2148 runs much happier on the medium grade shell than on the cheaper gas. I did have a nasty POW, which resulted in bent pushrods, or perhaps the bent pushrods caused the POW. After replacing the pushrods, and adjusting same, the backfiring stopped altogether. knock on wood. The 21 is a B&S engine which has a propensity to the bent pushrods. Fortunately for me, my neighbor is a wiz at those fine adjustments.
This problem can be several things. When your engine is cold, your computer is in a "closed loop" and just pretty much keeps the engine running until warmed up. After reaching operation temperature, the computer starts reading all the sensors. If one sensor is not connected or is defective, you will experience performance problems. Most of the time this will turn on the check engine light, but not always. Second is the fuel pump. This too will cause erratic engine problems.
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