BeaterShark

Under light throttle changes, my accel pump is not pumping gas (if it is pumping any, it's just dribbling out). It's not until about halfway through the pump travel do I get a good stream of fuel out. This is causing a major hesitation when coming off of idle. The engine pretty much just shuts off for about 1/2 a second. If I am real light with increasing the throttle, the car runs great, so I'm sure the problem has to do with the accel pump operation.

The carb is about 1 year old and ran fine before I swapped engines. I also replaced the accel pump with a new one and still have the problem. Where should I be looking to solve this?

lars

Chris -
I have found that there are a lot of bad accel pumps being sold. The rubber on the pump is not compatible with some of the additives that are currently in the fuels, and this causes the rubber on the accel pump to swell up, and the pump will jam up in the pump bore. This causes the pump to be ineffective for most of its travel, and produces the symptoms you describe.
You can buy individual pumps from NAPA. The pumps that I have bought individually from NAPA have always been of good quality, and they are compatible with the fuels. I have found some of the bad pumps in their carb kits, however. There are other brands of carb kits that also have the bad pumps in them - I just received a Q-Jet from a Forum member last night that had one of the bad, swollen, seized pumps, and this was a carb he had just had rebuilt by a "professional."

BeaterShark

Lars,
I bought an Edelbrock accel pump. Do you have any experience with these? This is also an Edel Q-Jet. Is there anything else I can check other than the pump itself? I know there is a check-ball. Is there any way to verify that it is working correctly?

Thanks for the help

clem zahrobsky

GM sell a spring part# 17083343 to preload the ball in the acc pump check valve which will help

BeaterShark

OK, I think I figured it out. The new Edel accel pump I put in was about 1/4" shorter than my original (you think I would have compared the lengths before I put it in) and the pump skirt on the original did not make a good seal. So, I swapped the pump skirt from the new pump onto my old pump and it works great now.

Thanks for the help.

Golden80

I used an Edelbrock pump when I rebuilt my Rochester and haven't had any problems with it. It was the same length as the one that was in it before.

Matt

73 LS-4

When you buy an accelerator pump, what exactly do you get in parts. I'm having a similiar problem to what Chris A is describing, with a Bog between 2nd and third shifts, which I can correct by keeping a little RPM up between the gears,(blip the throttle between gear changes so I'm not going from a full closed throttle to wide open). thanks for any info.

:cheers:
Pat Kunz

BeaterShark

I bought the Edelbrock P/N 1982. This included the pump assembly and the return spring.

The easiest way I can describe what that entails is that it is everything that is in the accel pump cylinder that comes out once the air horn is removed.

73 LS-4

Thanks, I think this will be the next project after I get the clutch in and the nose repainted, actually this was the project I was kinda working on when the vette decide the garage should be a little larger in front of it :eek:

:cheers:
Pat Kunz