Stewart Warner 240A Fuel Pump Switch Renewal

Randy V

Lifetime Supporter
There's a price to pay before you consume this information.
It's called Pay-it-forward. In other words - if you use this information, you're bound by agreement to help someone else.

The Stewart Warner 240-A-12 fuel pump has been out of production for probably 20 to 25 years at this writing (2009).
These pumps were manufactured to allow them to be serviced of literally all parts (some sub-assemblies) - but the parts supply has dried up along with that of the new pumps.

This thread is an instructional thread on the servicing of the Switch Assembly on the side of the 240-A pump.

Tools / Supplies needed;
* Drill motor
* Drill bits
* Razor blade / Xacto Blade
* Thin blade screwdriver
* Dremel tool with small cut-off disk
* 4/0 Emery - Polishing cloth
* Rosin Flux Remover or good Contact Cleaner
* Light machine oil
* Penetrating oil
* JB Weld Epoxy (original recipe - not the quick set)
* Brass Bristle brush (fine)

Here we go

The Switch assembly is on the side of the pump. It's secured with a hollow Aluminum retainer pin that fits through the side of the switch cover.

When I first tried to force the cover off by just turning it with a large wrench - I realized that it would not shear the lock pin. At least the adjustable wrench I was using did not have a good enough grip on the cover to turn it off.

I tried to pry the lock pin out but could not get a very good grip.

Never having seen one of these switches actually removed -
I thought of driving it through to the inside. I got very lucky here in that the lock pin is hollow and it essentially "compressed" up against the body of the switch itself. This allowed me to turn the cover off.

Here is what the lock pin looked like when I tapped it with a punch to drive it inside the cavity

My advice would be to use a like-sized drill bit and carefully drill the top of the lock pin off.

Removal of switch assembly

Warning! - Don't just twist the cap off and yank the switch.

Once the lock-pin is removed, turn the cap counter clockwise to get the cap to release from the pump body.

Carefully push the wire into the cap as you pull the cap straight off the pump body.

Pull the cap off far enough where you can properly see the full switch.

Using a razor blade or thin knife - carefully work the blade between the gasket and pump body.
Once the gasket is released - insert a thin blade screwdriver to pry the switch straight out. Do NOT twist the switch as you are removing it.

There should be a black O-Ring/Gasket that fits around the toggle end of the switch. Usually it stays put in the pump. If not - don't worry - but just the same - don't lose it... Make sure you keep the same orientation (don't remove it and install it again facing the other direction)..

If the copper connector tubes came out with the switch - carefully remove them by using the Xacto blade or razor blade to help pry the tubes up and off of the brass conductors of the switch.

Protect these little copper connector tubes - they are very delicate and (like the other parts of the pump) no longer available.

You can see that there is a vent hole in the top section of the switch's cover.

Using the fine brass bristle detail brush - clean the outside of the switch body and toggle area.

From here we're going to carefully prepare the switch for removal of the switch's cover.
While I did this operation while holding the switch in my hand - I'd advise a small hobby vice or some other means to hold the switch in a steady position for work.

Not in my 30's any longer (for a long while now) I used a lighted magnifying glass to do the cutting work and some of the finer operations;

Using your Dremel or other high speed hobby tool and carbide wheel -

Grind the crimps off carefully without cutting too deeply into the switch's cover plate (Switch Plate).

Carefully insert your thin blade screwdriver under the Switch Plate at one of the 3 exposed openings on the side of the switch and pry just a little at each of the three points (sorry - no picture of this operation)...

Once the switch plate is loose - lift it straight up from the switch body - Here is what you should end up with;

A few more pics of the switch assembly..

Contacts open

Cleaning of the switch and contacts..
I used a Rosin Flux Remover to loosen the corrosion in the switch as well as knocking down some of the varnish on the switch's contacts. While I did spray it liberally inside the switch, I remained cognizant of the plastic toggle (blue plastic with square window) and did not leave it submerged or wet for long. A Q-Tip swab was used in areas I had good access to. Compressed air was used to spray the loosened corrosion free from the switch.

Now to clean the contacts - There was a pretty fair degree of carbonized varnish on the contacts. I figure at some point in time, this pump was submerged in water and also had traces of oil inside. It was the burned oil (I think) on the contact surfaces that finally caused the demise of the switch.
To clean the contacts, I cut a strip of 4/0 Emery Polishing paper and inserted it between the contacts and drew it back and forth a couple dozen strokes - then carefully flipped the paper over to clean the other side of the contacts.

A couple more shots of the Rosin Flux Remover and some compressed air and the contact faces were once again in very nice condition.

Then I decided to instill just a couple of small droplets of oil on the fulcrum of the Blue Plastic Toggle using a syringe.

After cleaning the switch body inside and out -
I put a couple droplets of oil on the pivot of the brass switch arm and worked it in good.

Now comes the interesting part - the re-assembly of the switch;
The blue toggle was moved to it's outside position (Contacts open) -
Carefully slide the switch body down over the top of the switch cover - being careful to insert the brass switch arm into the center of the blue toggle.

Now we need to re-attach the switch plate to the switch body.
You may need a small pliers to squeeze the two back together again once you have found the precise orientation that the two parts once shared.

I used a little bit of the cleaner - again - on a cotton swab to make sure that all oils were removed from the surfaces I was about to bond together.

Using JB Weld epoxy - I put a few dabs around the same crimped area that we just cut free with the Dremel tool.

Let the switch sit for 24 hours for the epoxy to fully cure.

The Switch Cover (the part that has the Hex Head) needs to ground against the top of the switch itself.
Once the epoxy is cured, you will need to cut the excess epoxy that might interfere with the contact needing to be made between the cover and the switch. I used an Exacto blade for this task.

Now comes the tough part

Installing the switch back into the pump

The two thin copper conductor tubes that we rescued earlier are about to be put back to work. Ultimately these tubes are the conductors between the switch and the pump's solenoid coils. As you can see - they fit rather snugly over the brass conductors.

BUT this is not where they shall remain.

These tubes will be removed from the brass conductor pins and inserted into the two holders inside the pump body's switch cavity as the one shown below;

Next - make sure that the switch has it's gaskets installed
If the black O-Ring gasket is not on the switch or still stuck in it's well in the pump body - install it now on the switch as shown;

Suddenly it all makes sense and comes together

When installing the switch in the pump body - Carefully insert the two brass conductors inside the two copper conductor tubes and gently push the switch inside the pump body until it's fully seated.

Rotate the Switch's locking cover over the 3 pins - making sure that the retainer pin hole and hole in the locking cover will align once turned into position.

Install a new locking pin - the one used below was a piece of plastic golf tee with a dab of Hot-Glue to hold it in place.

There you have it.. Now - if you ground the pump and connect the switch wire to your 12v battery, you should be rewarded with a very rapid "THUMP-THUMP-THUMP-THUMP"......

I hope this is of some help to all you gear-heads out there...



GT40s Sponsor

If your switch is past repairing or you need a new one and or gaskets/seal kits, please email me on [email protected].
Awaiting delivery of first production models.
This is more an exercise in effort over adversity, just like my other reproductions of GT40 Gold parts have been.
Email: [email protected]
Great "How To" article. It's really nice to see people share their knowledge like this. I hate the whole knowledge is power attitude so why should I share attitude.

Randy V

Lifetime Supporter
Great "How To" article. It's really nice to see people share their knowledge like this. I hate the whole knowledge is power attitude so why should I share attitude.
Thanks Richard - It's nice to know that someone appreciated the effort I put into documenting this entire process..

I did receive two messages on this in PM.

One told me that I may be introducing a potential fire danger (fuel in proximity of the switch contacts) - I did nothing to change the operational design or parameters of the switch - so I don't feel that this is necessarily true. Also - the design of the switch and the seals used are actually quite ingenious and I feel safe.

The other seemed to indicate that I was pretty bold to put my (C) copyright watermark on my pictures. To that all I can say is that if I had not, I would bet you dinner that I would find my instructions and images for sale on eBay or elsewhere..
Great job Randy. Thanks for posting. If I had tried that i would have ended up with a very rare and expensive desk ornament.

Trevor Booth

Lifetime Supporter
well done, well documented,
you can restake the two parts together by cutting slots about 1/4 " apart midway between each of the original tags and bending over the lip on the switch body about 45º. The dremel slitting saw blade is ideal for this.
The epoxy is probably a bit easier, however I would suggest clamping the two parts whilst epoxy cures.

Ron Earp

Very nice write up Randy. And keep putting the copyright on the picture, else you'll find someone else making money off of it in some way.

You own the pictures no matter but it's strange someone would comment on the copyright. It's one thing if you're making your living at this but for most of us this is a hobby so I'm not sure why someone wouldn't share. I had one of these fuel pumps on a 65 Falcon that used to drag race. Hated the noise but I guess I wish I would have kept it. Keep up the good work.

Randy V

Lifetime Supporter
Update - Here's some factory Service Instructions. Obviously these instructions will tell you how to replace sub-assemblies rather than repairing them (such as the switch in this thread).


Randy, I have four of these pumps on my dining room table, in various stages of disrepair. I am just starting to look them over and figure out how they work. Do you have any other instructions that you can post a copy of (similar to above) like the materials that came with the pump? I ordered a copy from eBay; we'll see what the fellow sends me, but I would like to know what else is out there. As far as I can tell, I have four complete pumps, although I don't have the mounting clamps for two of them. But that wouldn't be difficult to bend up out of some sheet steel.

Randy V

Lifetime Supporter
Hi Jim,

Other than the Gasket Part Number list - This is the only other document (image) that I have.

If you like, you can PM me and we can go over any specific questions you may have either on the phone or in email.


Rescanned to PhotoBucket to get it bigger for you
Last edited:


GT40s Sponsor

I have the full SW documentation for rebuilding switch & pump body.
Its in PDF form.
I'll email it to you today.
Thank you both. I got the pdf files today and printed it. I have a battery around here someplace and I am going to try the pumps out, and see if anything happens. I have the impression that the only spares available for these pumps are either what Andrew has had made up (gaskets and seals and the rubber pulse chamber top) or what is available as NOS stuff- is that right? It appears from the paperwork that everything necessary to rebuilt these completely was available back in the day- you could start with a bare casting and rebuild the entire unit. Pity they didn't keep that going. Andrew, I will call you around six pm UK time. Thanks to all as usual.


GT40s Sponsor
Randy, or for that matter any other Forum members.
PM me your email and i'll send you the full set, incl bench setup instructions & flow figures.
Please dont go paying $ 10.00 on eBay for half of what i have.

Brian Stewart
I thought it might be worthwhile relating my experiences with rebuilding SW 240A fuel pumps, just in case anyone else was trying it and came up against the same frustrations I did. I have, over the past three years purchased three of these pumps (very cheaply) via eBay. The first one worked perfectly on arrival, and was duly cleaned and polished and looks great. The second and third did the familiar (to many of you) single “bump” and refused to function. After a good kick the second one decided to work, but only if it was switched on/off a few times at each start-up. OK, time to thank Randy and Andrew for their brilliant posts on how to rebuild these things, especially the internal switch. Following their instructions it is not difficult to dismantle the switch, spruce up the contacts and pivot and reassemble. A quick probe with a multimeter showed all was working as it should after fettling so the pumps were reassembled. With high anticipation I connected them up to the 12V supply and…. “bump”. Bugger! Pull both apart again and re-examine my work. Nothing appeared to be out of order. Reassemble and “bump”. Bugger again. OK, so what might be wrong? The “bump” tells me that the switch is closed, making the solenoid push the piston down, but the switch must be staying on preventing the solenoid from allowing the piston to go back up. OK, so I carefully moved the piston through its supposed range to see if it tripped the little lever in both directions. Yes, it did. So why was it not turning the switch off under its own power? I concluded that the piston was not travelling far enough on the down stroke and slacken off the intake valve a couple of turns to give it more travel. Connect up the power and voila! “bump, bump, bump, bump……”. So, the lesson is, do not tighten the intake valve much more than finger tight. I do not know if the little lever gets slightly bent out of shape over time or if the inside of the little square hole in the switch actuating mechanism gets slightly worn, or maybe just the internal switch gets very slightly out of alignment, but it appears that things only need to be out by less than a millimetre for the piston to miss out activating the switch at either end of its stroke. Result – a single “bump”. So, if you have a pump that goes “bump” and nothing more, try slackening off the intake valve a turn or two and see if your pump then goes “bump, bump, bump, bump……”. If so, maybe fit an appropriate shim or spacer before re-tightening and your pump should be sweet. If everyone already knew this, my apologies for the superfluous post…

Randy V

Lifetime Supporter
Good work Brian :thumbsup:

In the bunch that I have done now, the fix only failed one time. I thought that maybe the coil did not have sufficient pull so that one's still on my shelf...
I'll give it a try with your suggestion.. Maybe double-gaskets?

Still looking for replacement fuel filters.
Although the filter does not have to be in place for the pump to work properly..