Acceleration

[dcarey]

1978 Spider, 2 bbl weber. Car idles fine, when I accelerate, it pops (backfires) through the carb. I think it may be too lean. The jets are standard and the accelerator pump appears to be working. I have removed the EGR, air compressor and carbon filter (and plugged all the wholes). Any ideas?

[So Cal Mark]

make sure the ignition timing is correct, but more than likely it needs a new accel pump diaphragm and/or o-ring on the pump nozzle

[dcarey]

Thanks, I will check it out.

[majicwrench]

The pump nozzle on my 72 was about half-pluigged, cleaning it out with a strand of copper wire make a huge difference in the amount it pissed out, and really improved my acceleration.
Did this just start, or has it always done it??

[dcarey]

The pump nozzle on my 72 was about half-pluigged, cleaning it out with a strand of copper wire make a huge difference in the amount it pissed out, and really improved my acceleration.
Did this just start, or has it always done it??

The car is new to me and had not run in eight years, I disassembled the carb and cleaned it. I am cleaning the nozzle again now and installing a new acc pump diaphram.

[So Cal Mark]

the o-ring on the pump nozzle should be replaced too

[dcarey]

I ordered a rebuild kit, hopefully the o-ring will be included. On closer inspection, the pump diaphram is slightly blistered (but not ripped), so I am guessing it is not providing a full shot. This is probably the cause of the lean backfire.

[dcarey]

Thanks all, in the end, it was the accelerator pump, replaced the diaphram, engine accelerates with no backfire through carb.