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Fuel Pumps for the Big Healey, 1953-1967

By Roger Moment

Originally published in the Austin-Healey Magazine, February 1994

There is no reason to throw out a pump that is not working. Have your old pump rebuilt as a spare to carry in your car.

For most people, a fuel pump is just another part of the car, one which "ticks" in Austin-Healeys, is hard to get to, usually forgotten and best left alone. That is until your car slops dead for lack of gas or sputters and misses on occasion, usually going uphill under full throttle. Then it is usually your friendly mechanic who gets to set things right. But in fixing or replacing fuel pumps there are many choices that can be made. Do you go for an after-market pump that gets the job done, but is definitely not original? Do you replace the original pump (assuming it is still in the car) with another Healey pump, even if it is not exactly the same? Or do you try to restore the pump to its condition in days of yore? I believe that a properly rebuilt original pump, with added capacitor (as described below), can provide reliable service for a long time. Mine have been operating for 15-20 years.

For all my involvement with Concours over the years, I really hadn't given much thought to fuel pumps until lately. Being a bit of an "originality nut," I was curious as to which pumps used the 3" long shaft diaphragm (not available from Moss Motors, but from other sources), and which used the short 2 3/8" shaft (this one is commonly available). In researching this question, using parts books from BN1s through BJ8s, I started to sort out the differences between the various pumps. Some of this information will be of interest to anyone who would undertake to fix a pump themselves, and some will only be useful to those wanting to get even this little esoteric detail of their restoration done correctly.

There were three different fuel pumps used from the BNI through the BJ8: the round 3-inch round types (available as either the L or more commonly, the higher flow-rate HP types), the box-like LCS pumps and the round 2 3/8-inch AUF301 pumps. These pumps are described in the table 1 above and shown in photo 1. It appears that the shorter coils were introduced at chassis #13831, but this is based on interpretation of listed part number change points. The changeover to the step cap came atBJ828225, and reflects inclusion of a capacitor to reduce point wear from arcing. It is possible to use later pumps on earlier cars, at least from the standpoint of fuel delivery, and I suspect that the shorter coil assemblies were used on replacement pumps sold after about 1962, since they all fit interchangeably on the different cast aluminum pump bodies. This may be why most pumps found on cars today may have the correct pump body, but are fitted with short coils and stepped caps. (The points on all pumps are also interchangeable.)

Fixing Pumps

There are three main reasons why pumps fail: 1) clogged internal filters: 2) cracked diaphragms, and 3) burned out points. In many old pumps that I have examined, particularly those that had capacitors, the points were really not all that bad, and cleaned up nicely with 400 grit carbide paper, followed by polishing with 1200 grit ultra-fine.

If you have pump problems, it really is best to totally disassemble the coil from the pump body. This is the safest way to remove the points and avoid damage, and also provides an opportunity to check the diaphragm condition.

When separating the coil and diaphragm from the pump body, watch out that you don't lose any of the II brass washer-like spacers. You need every one of them to assure proper alignment of the diaphragm on reassembly. (Some rebuilt pumps may have a plastic spacer, which works fine, and is easier to install.)

Diaphragms in original pumps consist of two rubber layers, and this material will deteriorate and cracker become stiff over time from contact with fuel. This is why checking the condition is so important. More recent diaphragms from SU have an additional mylar membrane on the fuel side, which I suppose was added to provide protection from fuel attack and prevent this problem. It is important to install an additional gasket (Victoria British part #3-2012) between this membrane and the pump body, when using this type of diaphragm, as these materials will not form a properly tight seal by themselves.

To remove the points I recommend following the shop manual instructions and unscrew the diaphragm after separating the coil from the pump body. You will avoid 1) having to disassemble the pedestal assembly and 2) risking damage to the fragile insulation on the two wires as they poke through the coil body. If you are adventurous enough to take everything apart, it is possible to miss some fine points.

First, special two-turn helical spring washers were used under the various screws as lock washers. These are placed against the Bakelite, with connector eyelets positioned above and between them and the screw heads or nut. Second, a lead washer (Victoria British part # 12-5040) was added under the brass nut on the terminal post to assure good electrical contact. The proper order of assembly on the terminal post is shown in Figure 1. It is a good idea to refer to a parts book drawing to check the order of all washers, as they could be missing or incorrectly installed during previous servicing. The 100-6 or 3000 parts books have proper drawings (the 100-4 parts book has no illustration), and the electrical pedestal parts (except for the capacitor) are the same for all pumps.

Warning: Insulation on coil wires gets brittle with age — handle them very carefully. Electrical resistance on 3-inch-tall coils is 3.5 to 4 ohms, and on the shorter 2 3/8-inch coils is 2.5 to 3 ohms. Resistance should be infinite between the wires and coil case. Frayed leads can be resleeved — don't throw those old coils away!

Modern technology has come up with capacitors that are flat enough to easily fit under the Hat cap of earlier pumps, thereby giving electrical protection to the points while preserving the pump's original appearance. The original capacitors were pencil-shaped and rated at 200 volts. Photo 2 shows a mylar 0.047 uF capacitor, rated at 400 volts attached across the points—one end to the blade retaining screw and the other to the screw to which the flexible copper point lead goes. It sits no higher than the top of the adjacent screw, clears the points by an ample margin, and almost totally cuts out arcing. Cost is a whopping 35 cents.

To further extend point life, be sure that the joint between the cap and coil base is sealed to shutout air. Once the oxygen under the cap is depleted (after a few minutes of operation) arcing cannot be sustained. This is part of the reason why rubber hands and sleeves were originally used on new pumps, and tape is applied to rebuilt ones.

When reassembling the points, it's important to note the proper order of assembly on the terminal posts. Special two-turn helical spring washers were used under the various screws as lock washers. These are placed against the Bakelite with connector eyelets positioned above and between them and the screw heads or nut. Second, a lead washer was added under the brass nut on the terminal post to assure good electrical contact.

Caution: When reassembling components and the pedestal to the coil body, do not over-tighten the screws, you could crack the Bakelite.

Three styles of fuel pumps used on Big Healeys: (Fig 1) AUF301 used on later BJ8s; (Fig 2) the LCS found on later 100-6s and most 3000s, and Fig 3 the pump style found on BN1s, BN2s and Longbridge BN4s.

Adjustment of the diaphragm is quite easy, and is explained in the 100-6 and 300 shop manual (but not the 100-4 manual). If you are using aplastic spacer ring, be sure to install the coil spring and spacer before inserting the shaft up through the windings. By pressing in fully while turning, it is possible to engage the first thread into the rocker assembly. Continue to screw the diaphragm shaft until the rocker just throws over when the diaphragm is pushed fully upwards. Then back off 2/3 of a turn (count four holes on the edge). If you are using the 11 brass spacer rollers, they are best inserted after completing the rocker adjustment by lifting up an edge of the diaphragm to drop them into place. It is emphasized in the shop manual that the screws holding the coil to the pump body should not be tightened with the diaphragm in the relaxed position. You can make a simple tool, illustrated in figure 2, to reach in and hold the top of the spindle in its uppermost position, thereby stretching the diaphragm, while tightening the six body screws.

Finally, remove and clean the filter from the bottom of the pump body. This can be easily done with the pump in place on 100-4s, but is a bit trickier with the box-type on the 100-6s because of risk to damaging the rectangular gasket. These filters will most likely become clogged from particles sucked up from the gas tank. If this happens often, unscrew the drain plug at the bottom of the tank and flush it out. I run the tank down to about 1-2 gallons, and recycle this amount through a fine strainer until it runs out clean. Shake the car a bit to slosh it around for maximum pick-up of particles distributed across the tank bottom.

Remember, there really is no reason to throw out a pump that is not working. Many parts are no longer available, so it would be a shame to throw pieces away that could be salvaged to restore other pumps. Besides, you could probably have your old pump rebuilt as a spare to carry in your car.

Not what you were looking for? Don't forget you can check our back issues using the AHCUSA Magazine Index.

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