Fuel pump question

[Guest TINNDN]

I am in the process of fixing up a 46 Pontiac that has a dual diaphram fuel pump. The fuel pump doesn't seem to be pumping gas at all. I noticed that other day that there is nothing hooked up to the wiper line on the top of the fuel pump. My question is, could that be causing the fuel pump not to work or does that not effect the fuel pump because of it being seperate from the fuel portion of the pump. Thanks for ANY help I can get.

[Rusty_OToole]

It would not cause the fuel pump not to work. The 2 chambers are separate. The bottom one pumps fuel, the upper one pumps air.

To connect the upper chamber or vacuum pump you need to have a line from the intake manifold to the pump, and from the pump to the wipers. Right now you probably have a line from the manifold right to the wipers. The pump should be marked.

In operation, the manifold vacuum holds the pump open and it just sits there doing nothing. But if manifold vacuum drops off the pump kicks in and keeps the wipers working. This is to prevent the wipers stalling out on hills.

[Bud Tierney]

If you have the pump off you can usually tell whether the diaphragm is working by holding the pump and working the arm--you should get some noise, altho can't recall now if wiper part made sucking/pumping noise or not. If arm doesn't move, and'd been sitting, arm may've rusted in upstroke position=no pumping.

If setting a long time, diaphragm might've dried, cracked=no pumping.

I believe replacement diaphragms were available for awhile--the originals didn't do well on the new fuels/fuel mixtures??

Look carefully for filters/screens that may be clogged; if diaphragm bad and no replacement, you should be able to make a new one--neoprene??--can't recall what used, and may require something newer now. Good luck.

[Dave Henderson]

It was a common practice to bypass the vacuum diaphragm part of the pump when that diaphragm went bad. The fuel diaphragm is unaffected by doing that, and would continue to pump gas. This was a low budget approach that kept the wipers operational, except when there was a vacuum drop such as when going up hills. Suspect that is why there is nothing attached to that part of it.

[Rusty_OToole]

Best thing to do is send it away for a rebuild. If it has not been done it will need to be done soon. Today's gas eats up the old rubber parts. You need the new formula neoprene pump diaphragm and new valves.

[Guest GeorgeCagle]

I had mine rebuilt by for my '37 Studebaker by Then and Now Automotive (www.maritimedragracing.com/then_and_now_automotive ). It came back better than new. Even the screws and washers that hold it together looked new. I have put about 500 miles on it and it works great.

[Rusty_OToole]

You may be able to order one from your local NAPA or other good auto parts store.

[rons49]

Tinndn, I too in the last 2 years had Then & Now rebuild 2 AC pumps. The workmanship is excellant for $125 + shipping . Ron