New Briggs Vanguard Backfiring

[bgsengine]

Oh they will start they just wont RUN - solenoid will only close off the main emulsion tube, fuel will still be fed through idle circuitry but at WOT position the engine will be excessively lean - after enough cranking you may have enough fuel vapor to start a slow combustion that may still be burning slightly when intake valve is open.

Have had it happen before on a Briggs engine - no start just backfires, the fuel solenoid circuit was not grounded (someone did not hook up the ground wire)

Took the shade tree guy 2 days and several "Try it and see if it fixes it" parts (Coil, 2 new plugs, valve job, to name a few things he did) before giving up and it came to me - while checking it over I noticed the solenoid ground hanging loose, hooked it up and she started right up just fine - had to do a little bit of adjustment work and re-work of the other guy's "fixing" afterwards..

[KE4AVB]

That's a new for me to remember though as I probably have would check the wiring without giving it a second thought but that what I get for running on auto-pilot when it comes to electrical checks; 35 yrs of electronics will do that to you.

That like working on a copier using 120Vac circuit and having the neutral open. Most techs usually just reference frame ground and since they 120 vac dismiss a line problem. I seen one very good tech nearly pull his hair out after a week of troubleshooting and finally comment to me "This just doesn't make sense.". I ask if I could help being a lowly calculator tech. He said it won't hurt. I found the problem quickly as I had a lot problems with Army wiring at Redstone and automatically check the power source. Glad I did that plug had no neutral but the plug next to it had 240vac on it; no wonder the lady's electric typewriter sounded like a sewing machine. Now that's government work for you.

[RoyM]

I'm thinking a diode in the ignition harness is bad, both cylinders are firing at the same time. Disconnect the kill wire from one coil and try it, if the problem disappears you have your answer.
I wondered if the op is a dealer, if so he could replace the harness under warranty. If he is the end user and bought from a Briggs outlet, the dealer may or may not entertain warranty as Briggs technically will only authorize repairs on dealer installed engines. If he bought online it could be more difficult.

[Arkie]

Thanks for the explain.

A electronics tech gave me a very expensive piece of electronics test eq few years ago because he could not repair it and it was his own eq. He was pulling his hair out trying to repair the unit but no go. He needed the eq immediately in his business so he replaced it with a new expensive piece of equivalent test eq. The neon power light would come on indicating power applied but no go. I'm a electronics tech also and we worked together at same place for awhile and he had moved on to another job, but we remained frineds.

I called him couple days later and told him he could have his electronic tester back it was repaired. He asked what was wrong and when I told him it was ONLY a open Neutral wire broken inside the unit. He said, but the power light was on indicating power and it appeared to be a bad power supply. I said those neon indicators will do that even with a open N. He said to keep the eq and enjoy.

Open electrical neutrals are very dangerous and require a heads up at the higher voltages.