VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Gas seepage at '31 fuel pump

I continue to have some gas seepage at top of fuel pump for my '31, appears to be coming from around screw heads. I am reluctant to tighten screws further for fear of stripping/warping the casting, and am also concerned some gas may seep into block, although it appears the drain in the casting prevents that.

I have a new diaphragm made from laminated material, seems to be just fine but I notice the old one had a very thin cork gasket on top of diaphragm, seems to be adhered to it. Went to local gasket supplier and he suggested using 1/32" durlon (compresses about 10%) gasket material, and placing a gasket each side of diaphragm. I have the gaskets now made, but before taking pump off to do this, wondered if others had suggestions. BTW, I also plan to replace lock washers at same time, they are old and I am concerned they may not be keeping screws tight.

Sounds to me that your valves on the pump are leaking. Not the screws. Also all you need is one sheet of rubber stock....you don't need to laminate it.

When u say one piece of "rubber stock" what do you mean. The piece I took out was modern rubber, but it seemed to have stretched, and as indicated was leaking around the screws. I checked the valve nuts and they were tight no leaks.

In the box of spares that came with the car was an NOS diaphragm cut to size with the 6 outer holes in perfect alignment. All that was missing was the 1/4" center hole. The diaphragm was made of what appears to be a laminated belting type material, very flexible but appears very durable, and does not stretch.

So this is what I have there. I will have a good look for leak source before I remove it again.

As I write this it ocursa to me the rubber may have been too stretchy (causing it to pull away from screws) and the second one may be too stiff, also causing it to pull away from screws. Oh well I'll have to keep trying to find the best combo. Does anyone have the kit from FS, what is their diaphragm made of?Thanks for advice.

By "rubber stock", he probably means a diaphragm that is one piece of rubber and not laminated.

From your description, it sounds like your leak might have been coming from the diaphragm around the area of the screws.

The FS rebuild kit is very well done and worked great to rebuild my pump. The diaphragm is of a neoprene type material and, in addition, I do not use ethanol fuel any longer in any engine I own from a string trimmer to the 32.

Mac

If the diaphragm you used came with the car it may not be suited for use with alcohol. NOS in this case is not the best.

Just buy the kit from the Filling Station and rebuild your pump. You will be happy with the results.

I'm going to do 2 things, continue to experiment with the materials I have and order an FS kit. Thanks for advice.

See private message sent.

32 Confed you get top prize. Went out this AM and rechecked the valve above the diaphraghm and sure enough it needed about 1/8 of a turn or so to tighten. No leaks now. I've had trhis pump on and off 3-4 times and apart at least twice (due to buying the garbage one over eBay) and at some point must not have fully retightened the valve. Went for 2 mile spin, no leaks. On to the next thing which is trying to get my NOS Tillotson Carb tuned properly. But that will be a new Topic.

Thanks Gunsmoke, let me know how it works. I've built a lot of these pumps for people.