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One of the easiest, yet seemingly daunting, parts on your TR to rebuild is the fuel pump. This project covers the fuel pump on the TR2 through 4A cars but most of it can be applied to the TR6 and others. The most difficult part of the task on the TR2 through TR4A cars is reinstalling the lock washer and nut that hold the pump on the rearmost engine stud because of the breather pipe. The second most difficult part - removing that same washer and nut.

Let’s start with an understanding of the flow path to help better understand some of the logistics. Figure 1 shows the top of a typical TR2-4A fuel pump. #1 is the inlet for a compression fitting for the 5/16” fuel line (see figure 2). It seals by compressing an olive between the 5/16” tube nut and the tapered opening in the fuel pump inlet. This inlet leads to a hole on the underside of #2 that allows the fuel to enter the glass fuel bowl. When the pump operates, the fuel is pushed upward from the glass bowl through the mesh filter, and along a channel under #3 where it encounters a one-way valve under #4 that allows the fuel to enter the upper chamber of the pump body. Once here, the fuel is prevented from returning to the glass bowl by this one-way valve. When the pump diaphragm is activated by the pump arm, the fuel is pushed out another one-way valve under #5 and through the outlet at #6. The pipe at #6 also is a compression fitting but has a unique tube nut in that while the nut is the same size as a 5/16” tube nut, the pipe and olive are ¼”. None of the major parts suppliers currently carry this tube nut. However, the ¼” olive is readily available.

Figure 2 shows the compression fitting featuring #1, the 5/16” tube nut and #2, the olive. The tube nut is slipped over the fuel pipe. Then, the olive is slipped over the pipe and up against the bottom thread of the tube nut. The pipe, nut and olive are then inserted into the fuel pump. The tapers on the olive parallel the tapers on the inside of the tube nut and the pump. As the nut is tightened, the olive is compressed, sealing against the nut and pump opening. It is important to realize that these are not pipe threads. The threads do not do the sealing. It is the compressed olive that does the sealing as it is compressed and moves outward against the inside of the tube nut and the inside of the fuel pump inlet.

You must first remove the tube nut taking fuel from, the fuel pump to the carbs. There will be fuel spilled so it is a good idea to have a shallow pan such as a cookie sheet or baking pan under the frame, just below the left side of the engine and some cloths handy. There will be a small amount of fuel flowing back from the carbs when the outlet is removed (figure 3). Pinch off the fuel flow to the fuel pump at the rubber hose before the steel pipe with the compression fitting entering the fuel pump. You can now remove the rubber hose from the inlet fuel pipe.

The glass fuel bowl (figure 4) will likely be filled with gas. You can remove it now while it is held vertical by loosening the knurled knob at the bottom of the glass bowl, swinging the bracket to the side and slowly lowering the glass bowl. Note, there is a filter screen held in place by a gasket. Originals were cork gaskets and most rebuild kits have rubber gaskets. If you wish, you can remove the glass bowl later when dismantling the pump. Either way, be careful so as to not spill the fuel in the bowl.

The original pump is held in place by a lock washer and ½” nut on two studs coming from the engine block (figure 5). The forward nut is pretty straight forward but the rear nut will require some finicky work because of accessibility issues. Access to the rear nut is limited by the fuel pump and the breather tube. I would suggest using a ¼” drive ratchet, a short extension, and ideally a universal ½” socket. In a pinch, a standard ½” socket will work, but be careful. As the nut comes close to the removal point, the socket may jam against the body of the pump. Also, note, on the rear stud there is a ‘P’ clip holding the oil pressure pipe in place. Take note of its position so you reinstall it correctly. Once the fuel pump has been removed, you do not want to roll the vehicle in gear which may turn the cam and get the cam out of phase with the arm on the fuel pump.

Once the pump is removed from the vehicle, you can unthread the tube nut holding the fuel pipe to the inlet of the pump. begin the disassembly by removing the six, pan head, machine screws that hold the top to the main body.

Let’s take a closer look at the main body of the pump. The pump body is separated from the top portion, where the fuel enters, by a diaphragm and plunger (figure 6). The diaphragm pulls fuel into the upper chamber and then pushes it out to the carbs. The plunger is activated by the arm that sits inside the engine block. The arm is moved by the camshaft as it rotates.

The diaphragm and plunger can be removed by rotating the diaphragm 90°to release it from the arm. It can then be pulled straight up.

Early pumps and some of the better repro pumps now available, featured a priming lever (figure 7 - #1). The arm (figure 7 - #2) that makes the pump work sits inside the engine block and rotates about a pin (figure 7 - #3) through the pump body. Early pumps secured this pin with clips whereas some repro pumps without these clips have reported problems with the arm detaching from the body causing the fuel pump to not only fail, but to do serious engine damage as well, should the arm jam inside the block.

The only other pieces requiring removal are the inlet and outlet valves. Take note of the orientation of the valves so they are installed the correct way around. Fuel enters the flat side and flows out the domed side. On early cars, the two valves were held in place by a valve clamp (figure 8) and figure-of-eight gasket. Removal is easy, just remove the two screws, slip out the clamp and lift the valves. Make sure the screws are reinstalled tightly otherwise they may fall out, causing the valves to drop out and the pump to fail. 

On later cars, the two valves were peened in place. Figure 9 - #1 shows the inlet valve and #2 is the outlet valve. This photo also shows several peening marks suggesting the pump may have been rebuilt in the past.

For these valves, use a box cutter to remove the soft metal peened over top of the valve or a Dremel. Be careful so as to not remove more metal than necessary. Once all the metal is removed, the valves can be removed easily.

Some other things you ought to know about this range of fuel pumps. Some of the repros, such as those provided by Moss a few years ago, featured fittings (figure 10)  on both the inlet and outlet openings because of weak body metal and/or poor threads. There also is a Canadian made version without the priming lever.

Original fuel pumps also featured a rubber seal in the tube where the plunger resides. It may be difficult to see in Figure 11 because of the lack of contrast between the black rubber and the dark tube. Some writers suggest the purpose of the seal is to keep the fuel out of the engine and while this might be possible should the diaphragm fail and allow fuel to leak through, the true purpose of the seal is to keep oil out of the lower pump body because in a normally functioning pump there should not be any fuel in the lower pump body. 

The Moss repro pump shown in Figure 10 features a different type of rubber seal. Many pump rebuild kits do NOT include the rubber seal suggesting that it is not necessary to have a seal in this location. If you do not have a seal here and your pump fails, be sure to check for fuel in the oil as this could damage the engine. The seal used in this repro pump is sometimes available on eBay. It seals by being pressed down onto the retaining ring shown in Figure 12.

Additionally, there is a repro pump made in Canada that does not have a priming lever. The Canadian pump has six shouldered (washer-like) screws (figure 13-#1) rather than the pan head screws to secure the two halves together. It also has no c-clips (figure 13-#2) holding the shaft about which the arm rotates. When you obtain a rebuild kit from your supplier, you should ensure the bits will fit the type of pump you have.

When you shop for rebuild kits, there is a great variation in price. Many kits do not include the rubber seal to which I referred earlier. As you will see in figure 14, the original one I removed was in a rather perished state.

One of the more expensive kits is TRF’s. They justify the higher price by noting they DO include the oil seal and also upgrade the diaphragm and the inlet/outlet valves. There are some who suggest the rubber seal is not needed. You can decide for yourself. The oil in the engine where the fuel pump is mounted, is not under pressure. However, some have reported that without the oil seal, oil is slung into the lower body of the fuel pump. This cavity is not sealed. There is a breather hole in the side and some have reported loss of oil through this breather hole. In a properly operating pump, any oil in the lower chamber is kept separate from any fuel in the upper chamber by the diaphragm. Should the diaphragm fail, that is no longer the case. The rebuild kit shown in figure 15 features the rubber oil seal missing from most rebuild kits (drawing used with permission of The Roadster Factory).

If you purchased a kit with the oil seal, you will have an extra step-replacing the oil seal. The original oil seal is held in place by a retaining ring that is crimped in place. In the example shown here, there were three crimps that seemed to have been applied hydraulically since all three were uniform and had relatively smooth edges. Figure 16 shows the three crimps. I used a Dremel tool to carefully grind down the crimped material. Work slowly and check for removal often so as to not remove too much material.

When enough material has been removed, you should be able to lever out the retaining disk. I used the handle of one of these dental picks (figure 17). The handle can be inserted through the centre hole of the oil seal and then levered side to side as you move around the circumference of the retaining ring.