I'm posting this to help some of you that may have this problem.
Accelerator pump pull over is when the accelerator pumps flow gas at certain RPMs when the pump isn't even actuated by the pump cam. usually caused by vacuum through the venturi across the pump nozzle pulling fuel out of the nozzles!
Ive worked on 2 new Holley double pumpers in the last month on engines that were running rich that had Accelerator pump pull over at speed!
Even on the secondary's when the secondary throttle plates were closed ( no Vac. through the venturis) That really threw me:confused: because there was nothing to cause the fuel flow through the pump nozzles? I changed nozzles to no avail and tried other normal remedies no help! And pulled the pumps to find a rubber check instead of a check ball on the fuel bowls! I tried changing fuel bowls to the ones with check balls and it cured the problem!
I called Holley and talked to a tech about it and was told the rubber checks can vibrate at certain engine RPMs and actually pump fuel out the nozzles that's why the secondary pump nozzle was pumping fuel even though the secondary throttle plates were closed!!!!
This morning I did a search and found this Video!!!!
I hope this helps some of you that may not even now you have this problem at higher RPMS with the rubber pump checks:thumbup:
Jester
Accelerator pump pull over is when the accelerator pumps flow gas at certain RPMs when the pump isn't even actuated by the pump cam. usually caused by vacuum through the venturi across the pump nozzle pulling fuel out of the nozzles!
Ive worked on 2 new Holley double pumpers in the last month on engines that were running rich that had Accelerator pump pull over at speed!
Even on the secondary's when the secondary throttle plates were closed ( no Vac. through the venturis) That really threw me:confused: because there was nothing to cause the fuel flow through the pump nozzles? I changed nozzles to no avail and tried other normal remedies no help! And pulled the pumps to find a rubber check instead of a check ball on the fuel bowls! I tried changing fuel bowls to the ones with check balls and it cured the problem!
I called Holley and talked to a tech about it and was told the rubber checks can vibrate at certain engine RPMs and actually pump fuel out the nozzles that's why the secondary pump nozzle was pumping fuel even though the secondary throttle plates were closed!!!!
This morning I did a search and found this Video!!!!
I hope this helps some of you that may not even now you have this problem at higher RPMS with the rubber pump checks:thumbup:
Jester