The Unobtanium File: Saving An Ancient Caterpillar Fuel Pump Made of Solid Bronze With Skill and Crafty Thinking

The Unobtanium File: Saving An Ancient Caterpillar Fuel Pump Made of Solid Bronze With Skill and Crafty Thinking

Welcome to the Unobtanium File, a randomly reoccurring blog series that will highlight some of the more interesting, off the wall, and down right cool projects that the dudes and dudettes at Then and Now Automotive in Weymouth, Massachusetts are working on. We’ve done lots of stuff with Then and Now because the place is bad ass beyond words. The work they do and the parts they have will literally blow your mind. If it hasn’t been made in 50 years, they probably have 100 of them. If it hasn’t been made in 100 years, there are probably 50 of them. I once saw about 10 aluminum heads for Essex cars dating back like 100 years, but that’s another story for another day.


Today’s trip into the Unobtanium File deals with a fuel pump from an old Caterpillar tractor made of all things…solid bronze!

Before we get to the actual project, we wanted to give you some background on mechanical fuel pump history and to do that, here’s Then and Now’s owner Tom Hannaford who is one of the great automotive historians and story tellers we’ve ever met (and trust us…we’ve met lots!) –

Some car makers jumped on right away issuing mechanical fuel pumps in their 1928 models, others waited. Hudson waited until 1933, becoming the last major maker to join modern times.

Truck and equipment makers mostly stayed with the old technology (gravity fed fuel systems) they were familiar with. It worked OK and in large vehicles it was easy to get enough height above the motor for gravity to work fine. Tractor Trailers stayed with huge, heavy duty vacuum tanks well into the modern era. So did many construction equipment makers except Caterpillar.

Caterpillar’s equipment was often not operating on a level surface, so the problems with gravity tanks or vacuum tanks were very real customer complaints to them. When they could get a mechanical pump, they switched to it, but they were making equipment that mainly lived outdoors. They also made a tough, bombproof product, so they wanted a pump made out of something equally tough and outdoorsy…Bronze.

AC Spark Plug was in the process of creating the market for mechanical fuel pumps, making them in die cast zinc. However they were not alone in the fuel pump business, a major maker of vacuum tanks had seen the writing on the wall and was also beginning to offer mechanical fuel pumps. Stewart Warner was the little guy in the field, up against a division of mighty GM, so they could be more flexible. They too were mostly working in die cast zinc for the vacuum tanks and their own mechanical fuel pumps, but for a good customer ordering thousands of pumps, making a pump in bronze was not out of the question.

So Stewart Warner made bronze pumps for Caterpillar, and things went along smoothly for a couple of years until AC noticed that Stewart was making a dent in the money AC could be making if the were the ONLY mechanical fuel pump maker. AC had had their engineers busily creating and patenting their mechanical fuel pump designs, while Stewart had worked the old fashioned way- they looked at what the other guy was building, and made something just like it but different.

By 1932 AC was convinced it was NOT different enough, so they set the GM lawyers onto Stewart and by 1933 the courts had agreed, and suddenly Stewart had been forced out of the mechanical fuel pump business, and AC now owned the factory Stewart had built the pumps in, along with all the parts, tooling, and all the contracts to supply pumps to the gas and diesel engine makers, including Caterpillar. AC was able now that they had no competitors, to offer attractive terms to all the other makers to simply abandon the Stewart contracts and switch over to an AC pump made to do the same job. Except to Caterpillar that is!

Cat wanted a bronze pump, the contract said bronze pump, and by damn they were going to get a bronze pump! That left AC in an odd spot. Their modern factory did not do bronze, but the old Stewart plant could, plus all the parts and tooling were there so from 1933 until the contract ran it’s full term in 1940, AC made bronze Caterpillar pumps in the old Stewart factory. The only concession they got from Caterpillar was they were allowed to change the casting dies to remove the Stewart logo and replace it with the AC logo and the new AC part number for the Stewart part.
These Cat pumps exist in four forms. Original all bronze pumps with Stewart Warner raised out of the castings, all Bronze with AC logo and part numbers, a hydrid version as 1940 approached in which the body of the pump was die cast AC with the fuel cover on top in bronze with AC logos and numbers, and the last version made after 1940, in which the pump is all zinc die cast and carries AC logos.

There could be more to the story. Did the court just throw the factory to AC instead of making Stewart shut it down? Or did some smart AC lawyer with some engineering in his background figure out that they would NEED that factory to fulfill the Caterpillar contract, and fought to get it? Who knows! – Tom Hannaford



What we DO know is that Mike Casella at Then and Now opened a box and saw one of these bad boys staring right back at him. Like the old parts ninja that he is, Mike went to town on the pump, came up with some creative solutions to fixing the parts that event he couldn’t get his hands on and ended up with a fuel pump that deserves to be displayed at the Smithsonian as opposed to being bolted to a big old Caterpillar tractor! (Although it is a totally cool old Cat that has been restored to the nines).

Scroll down for the photos and captions that tell the tale of how one solid bronze fuel pump was saved and now works like a champ!

Here’s the ugly bastard upon arrival. While interesting looking, Mike winced at the smell and the fact that it looked to have been plucked from a grave.


Despite the fact that it looks like hell externally, it is a neat looking component, right?

Hey, maybe all the internal parts are still in great shape, right?

No, that would be wrong. Lots of gnarled, junked stuff in there. Luckily, most of it is out there to be found, but a couple pieces aren’t.

These two little pieces provided the problem. Those are the original “filters” which are really stacks of tiny brass wafers. They would catch sediment and bad stuff before it got to the engine. The problem? You aren’t buying or making these anywhere on planet Earth.

Another look at the cool, but irreplaceable “filtering system”.

Here’s what the stand and the filters look like pulled apart. Mike had to go into thinking mode to come up with an effective solution that would fit in the glass fuel bowl that the pump had.

Like we say here at home, Mike is WICKED SMAHT! His solution was to walk over to grab a carb fuel filter from a Q-Jet and compare it for size.

Since these filters have a one way valve, Mike remove that and forged ahead.

A little crafty machine work and voila! The filters were mated to the head and they fit like they were designed to be there.

That nifty little plate holds the filters in position and allows the spring that lives inside of the fuel bowl to keep them in position.

Like we said, this is just too cool! Problem solved. Want to see the rest of the finished product?

Just bitchin!

We’re surprised Mike sent this one back. It is just beautiful!

The end of the story? The customer was totally pleased and all of a sudden the ancient Caterpillar community had a new group of heroes in Weymouth at Then and Now!


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3 thoughts on “The Unobtanium File: Saving An Ancient Caterpillar Fuel Pump Made of Solid Bronze With Skill and Crafty Thinking

  1. john

    What about the “rubbers”? Lordy…don’t forget the rubbers (gaskets I mean) !!! 🙂

  2. jim

    you could always ahve the original wafer filters ultrasonically cleaned. i have seen this done with antique stationary engines. they have all kinds of wafer and sintered bronze disc filters, all of which are irreplaceable.

    a few hours in a large ultrasonic cleaner and they can be air hosed out and if needed, acid cleaned.

  3. Mike

    Update** Caterpillar offers the original style filters now.
    Update** Our web site link has changed to ;

    Since this story first ran, I have re-invented a few more parts for these pumps. Every few weeks another one of these pumps shows up on my bench. The last two came from New Zealand.

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