Rebuilding a Mechanical Fuel Pump

Written by Brian Klea. The original article can be found here.
Edited by Will Marsh

So it's time for a new fuel pump?

Having trouble finding one? Or perhaps you just can't bear to throw away that heavy, original, screw-together, Ralph-Nader-unapproved-glass-sight-fuel-bowl, genuine brass fittings, OEM-correct, actually manufactured by hand rather than pressed together by a machine, original fuel pump? A replacement tin, machine-crimped, Auto-Zone $30 special just wouldn't look right? I took another look at the original pump -- mentally acknowledged for a moment that the glass fuel bowl sight would make a great shot glass -- and then decided that I can't, in good conscience, place this six or so pounds of precision aluminum and brass castings into the trash never to be seen again.

Besides, as I found out, in the case of the pump for my '70 1100 D pickup, even a machine-made, offset filter-style pump is now unobtainium. Therefore, the only other easy and quick option is to replace the original pump with a Scout-style generic pump, re-route the hard lines and install an inline filter. Or, possibly perform a rebuild on the original. Choosing the latter option, I naively phoned Napa and asked about the availability of a rebuild kit. The counter-jockey laughed heartily and said he hasn't seen a rebuild kit available in 20 years! "Besides," he offered helpfully, "just get a new pump, they're pretty cheap." With that comment in mind, I figured if I tried to explain my obsessive sentimentality toward an obsolete, inanimate mechanical object, he wouldn't understand and would just probably laugh even harder. Besides, he should have known he was going to get a bizzare request as soon as I said "International Truck;" principally being, of course, an obsolete, inanimate mechanical object in and of itself.

Thus began the Sisyphean task of finding a rebuild kit. After making lots of phone calls and hearing plenty of laughs on the other end of the line, I find a guy in Massachusetts who's not laughing. Turns out that making rebuild kits for obsolete pumps is what he does. In fact, if he doesn't have a kit in stock for your particular pump, he'll make one for you for a slightly higher cost if you send in your pump! When calling to make an inquiry, you need the pump number which is found on the pump flange where it attaches to the engine block. Most likely you will have to remove the pump and clean all of the gunk off the pump body for this number to be visible.

Here's the link: http://dragsite.tripod.com/then_and_now_automotive.htm

International, being International, used various suppliers for their pumps: The two which I've identified as OEM for my truck are a KEM 1096 (glass filter bowl and screen) and a Holley pump (aluminum bowl with paper filter.) Here's how I rebuilt the KEM pump:


Here are the two OEM pump possibilities as described above. The photo shows all of the old parts removed from the pump, replaced by identical parts from the kit. The newly-rebuilt KEM pump is on the right, the un-rebuilt Holley on the left.


Removing and replacing the diaphragm: This is the part that typically fails on a pump. Telltale signs of imminent failure tend to be fuel weeping from the sides of the pump around the center diaphragm gasket. This means that the nitrile rubber is becoming cracked, brittle, and thin. To remove the diaphragm, the actuating lever must be removed. This is best accomplished with a careful bench grinding of the end of the soft-metal retaining rod. Once the end is ground off, press the rod out with a punch. (A new one comes with the kit.) The actuating lever and spring are removed once the "hook" from the lever is taken off the diaphragm rod. The pump casing that houses the diaphragm contains a conical rubber seal that seals the rod against the engine oil coming from the block. This is replaced by carefully tapping away a pressed metal seal housing, replacing the seal, and pressing the housing back into the recess of the pump body. The new diaphragm is placed into the body allowing the "hook" from the actuating lever to seat into the hole in the rod. A new return spring is attached and a new soft-metal retaining rod holds the assembly together. The end of the new rod is covered with a washer and then cross-punched with a flat chisel to keep it in place.

Here is the central casting of the pump containing the two chambers, each with a one-way valve pressed into the body of the pump. These can be carefully knocked out with a hammer and a punch. The new valves press in very carefully with a vise. For those familiar with pressing seals, etc., usually the tool of choice is a similar size socket to fit the outside of the seal. Here, sockets were too thick so I made a press-tool out of a piece of pipe with the threads ground off as shown in the photo. It was a perfect diameter to press in the new valves with a bench vise. In the photo, the old valves are to the side of the pump body. Interestingly, the new valves were of a slightly different design encased in a much heavier-duty valve body.

Here, the diaphragm body is re-attached to the valve body with screws. Each screw is slightly snugged by hand and then tightened in a cross-wise fashion, just like lug nuts.


The base of the pump is now screwed to the valve body. In between is a fresh gasket supplied in the kit known as a "pulsater gasket."


Place the fresh bowl gasket in the housing and re-attach the "shot glass," er, fuel bowl onto the pump housing. The Holley contains a paper filter in the bowl, this KEM pump only has a fine, brass filter screen.


For comparison purposes, this photo is an "exploded" view of the Holley pump. From what I've seen, this is the more common fuel pump. It is very similar in design to the KEM with the principal differences being: A) Easier to remove internal valves. The valves are pressed on pins rather than completely into the housing. B) The actuator rod retaining pin is reusable and held in with bendable tabs on the pump housing.

All in all, it was about an hour-long job, including removal and replacement from the truck. The end result is that an erstwhile obsolete, inanimate mechanical thingy that uses glass to hold back explosive liquid in an automotive application is now re-bolted to an even larger obsolete and inanimate object known as a 1970 IH 1100 D 4x4 Pickup Truck!