Stewart Warner pumps

**brianstewart** · 10-28-07, 03:51 PM

I have just acquired two original 240-A SW fuel pumps. One has the little rubber cap on the top (over the pressure regulating nut) split, the other has it missing. What function do these caps serve and how essential are they? Anyone know of a source of new ones if they are needed?

Thanks,

Brian.

Doc Watson · 10-29-07, 03:55 PM

Not sure about a source for new ones (I could do with 2 myself!!) but I do have the original service manual for the pumps.

The manual states that the assembly at the top is part of the pressure regulator. It also states that the rubber end piece is a 'pulse chamber' although I cannot see any reference to it in the manuals.

Hope this in some way helps

Andy

**brianstewart** · 10-29-07, 04:28 PM

Thanks Andy - looks like it is needed.

Big-Foot · 10-29-07, 07:07 PM

I always thought that the cap only protected the threads on the regulator screw.. Hmmm...

Andy - do you have any other exploded diagrams of these pumps?

Jimmy M · 10-29-07, 08:08 PM

Only guessing but I would think the 'pulse chamber' covers the opening and allows air movement when the diaphram moves while regulating pressure.

You could probably just put some sort of filter on/in it if you cant get originals.

Just an observation, I may be completely out of left field........

JM

Doc Watson · 10-31-07, 04:11 AM

Randy,
Yes I do have more exploded diagrams of the pumps, send me a PM and I will email them to you.

Andy

Trevor Booth · 10-31-07, 08:43 AM

I have run SW pumps with and without the rubber cap. It does not make any difference to its operation but I would suggest that if you had a solid rubber plug it would build up pressure in the upper chamber and may well affect the operation of the pump.

John Fitzpatrick · 10-31-07, 06:48 PM

Is the regulator on the SW pump good enough to run without a second regulator in the line, or should it be run wide open and regulated closer to the carbs?
John

Trevor Booth · 11-01-07, 07:11 AM

If you look carefully at some of the original car photos they did use a secondary regulator /filter unit. I have not found a need for this and use the SW regulator without any issues cranking 470HP on Webers.
What you do need to do is be very precise setting the pressure on both pumps exactly the same, this is the reason I believe they used a single regulator. If they had to replace a pump in a long distance race they would not need to worry about setting the pressure. When setting the pressure do not rely on a gauge, I use a piece of plastic tube taped to a graduated board and held near vertical at the carburettor fuel inlet and with the zero graduation at the same height as the fule inlet.
the height that the pump sends the fuel up the tube is then read off the graduated board. The height in feet X 0.434 = psi.