18hp vanguard won't start - backfires

Route 6x6 Discussion Board: Shop Talk: Tech Tips and Q&A section: 18hp vanguard won't start - backfires
Top of pagePrevious messageNext messageBottom of pageLink to this message   By rhawkins on Unrecorded Date: Edit

My '94 max II won't start. It turns over and tries to fire, but won't idle. Then it will begin to backfire. Any clues?

Top of pagePrevious messageNext messageBottom of pageLink to this message   By rhawkins on Unrecorded Date: Edit

Mystery solved.

I had only one spark plug firing. When I first tested for spark, I only tested one side...not both. Turned out to be a bad spark plug.

So this is one for my log book.
Symptoms: Fires, but won't idle
Carb floods
Backfires

Secondary issue: Excess fuel fouled the remaining good spark plug.

Solution: Check for spark on both sides. A v-twin will not run when only one side fires.

Now I can go work on the winch, lights and outboard motor. :-)

Top of pagePrevious messageNext messageBottom of pageLink to this message   By roadwolf on Unrecorded Date: Edit

one or two bad spark plugs

Top of pagePrevious messageNext messageBottom of pageLink to this message   By rhawkins on Unrecorded Date: Edit

Started out as one. The second failed while trouble shooting the problem.

Top of pagePrevious messageNext messageBottom of pageLink to this message   By Fred Sowerwine, Montana's Max dealer (Fred4dot) on Unrecorded Date: Edit

Don't mean to be argumentative, but I think you have water in your gas/ maybe bad gas/maybe two bad plugs. I have found (I believe others also have found) that a vanguard twin will run and idle just fine with only one good plug - no power though and exhaust will be smoky.

Be sure to check your oil, and if overfull, change it. If an engine runs very much on only one plug, the fuel that doesn't get burned goes right into the crankcase.


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