Fuel Pump
 

Noticed tonight that the fuel vent hose from my mech. fuel pump actually pumps OUT air...This is probally a stupid question but Im assuming it is supposed to....right? It pumps it out in very quick bursts and my fuel pressure guage moves with each burst (only about 1/4-1/2lb).....Im running about 6 lbs of pressure and if I plug the hose the fuel pressure drops to about 4lbs... Im pretty sure nothing is wrong here but Ive never read anything about the vent tube/hose actually pumping air OUT or a blockage of this vent hose causing low fuel pressure.....Thoughts anyone....

BH

I would have to think that since it is on the back side of the moving diaphram, you will actually have a vaccum/pressure cycle going on if it could be measured fast enough. It's gotta be normal. By plugging the line, you are probably restricting the movement of the diaphram a bit, hence the lower pressure reading.

This is normal. That vent line must be hooked up to your carb. In case the diaphram ruptures, this line will dump the fuel down the carb bowl.

Yeah I understand it's use I just was surprised about the pressure issue. Heck I have seen many people zip-tie them to their fuel line going to the carb...A little tight with the zip-tie (And I mean a LITTLE!) and your looking at 1lb or moore of fuel pressure loss easy! Not to mention any back-pressure probally would put extra wear on the diaphram....

BH