Backfires sometime

[canyonken]

1996 4.3 liter V-6. Had the mercarb 2 barrel rebuilt end of last season. Idles real smooth, runs great, starts just fine. Sometimes when applying throttle to get on plane it will hesitate just a tad and backfire once maybe twice and then run strong again. I replaced plugs, wires cap and rotor and fuel/water filter end of last season too. What causes a small backfire when getting up on plane ??

 

[tpenfield]

Re: Backfires sometime

Could be little lean . . .

 

[mpdive]

Re: Backfires sometime

Starts great, idles great, runs great at cruise, indicates that the idle circuit and main metering are within parameters. Your problem lies within a lean condition problem in either the enrichment circuit of the carb (accel pump, power valve) or possibly a timing issue. Some carbs have two settings for the accel pump rod, and mercury has resorted to using various rod holes depending on performance issues. There is also a debate over eliminating the check ball in the accel pump bore or leaving it in. Verify timing and no vacuum leaks before commiting to carb problems.

 

[canyonken]

Re: Backfires sometime

thanks.
I will look at timing and vacuum leaks first.

 

[canyonken]

Re: Backfires sometime

It is fixed.
No vacuum leak.
It needed timing adjusted and the carb float adjusted.