Using your stock motorcycle fuel pump in a BEC

    Last update: 1/18/10
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  Legal notice: (The SMA stuff.)
Working on a fuel tank can be very dangerous!


In other words, if you copy what I've done here and blow yourself up, I take no responsibility for YOUR actions.


Originally I was using an external high pressure fuel pump made by Mallory (MSD #2225, 125 #/sq" max, 43 gal/hr max.). This pump worked fine but was rather noisy and I really didn't think that I needed a pump that was probably big enough to run a NASCAR engine!

A friend of mine gave me a 1991 Mazda MPV fuel pump assembly and  I studied it with the idea of mounting it in my fuel cell. After I disassembled it from the mount I thought that it also looked too large for my 988 cc engine.

I had the original GSXR-1000 fuel pump from the motorcycle. At first it just didn't seemed possible to use the pump since it was designed to be mounted on the bottom of the fuel tank.  I just could not visualize having the pump hanging down below the bottom of the fuel cell.

When looking at the stock GSXR fuel pump assembly it is very compact and it is hard to even see the pump itself since the fuel filter covers most of the pump. The over pressure relief valve is built onto the pump and dumps the fuel directly from one end of the pump cartridge. This makes the pump unusable as an external fuel pump.

After studying the GSXR service manual, I decided to remove the pump from the mount and see if there was some way I could adapt it to my car. The rest of this article is how I managed to do just that.

I'm using a 10 gallon JAZ fuel cell with the following specs, 24"L x 12"W x 9"H  with foam insert blocks.

Things to consider when working with any fuel tank:

Of course the most important thing to deal with if your tank has had fuel in it is,


Other than that minor point the job is rather straight forward (gulp).

You have to keep this in mind at ALL times once the tank has had fuel in it. Years ago at my local junk yard there was a car that had been there for at least 5 years with the inspection cover on the top of the gas tank removed. There was no liquid fuel in the tank. One of the workers was using the flame wrench to cut some metal loose under the tank and he accidentally cut into the tank which EXPLODED!  He survived but it wasn't pretty.

I would imagine that the heat caused the sludge or varnish in the tank to vaporize and the fumes exploded. SO DON'T TAKE ANY CHANCES. Keep sparks or heat away from the open tank or disconnected fuel lines. When you have to use a metal wrench etc inside the tank make sure that you touch a metal part of the car beforehand to bleed off any static electricity. When I was connecting metal parts inside the tank I usually touched the part that I am about to mount the part onto. (While keeping my eyes closed and mumbling a Lucas laudatory.)

You can't just lay the pump down in the bottom of the tank because when it starts to run there is a good bit of torque exerted and the case of the pump tends to spin. Also you don't want the wires to the pump to just lay around loose in the tank.

Your motorcycle pump mount may look different from my Suzuki GSXR pump but I have an idea that the pump cartridge itself will be the same and this article will probably apply.

OK, now all that is out of the way, we can get to how to convert your motorcycle pump for use in a BEC.

But first, .... we have to take the thing apart to see what we have to work with.

Disassembling the GSXR-1000 fuel pump.

To see an enlarged view of most pictures, left click on a picture or right click and select "View Image".
Pump outside

This view is the of the stock  fuel pump. Normally it is mounted on the bottom of the motorcycle fuel tank. 

The pump in this picture is actually upside down from how it is used on the motorcycle.

Pump filter

This picture shows one of the two screws that holds the pump components together.

The pick up filter is located inside the domed cover of the pump.

Pump thermistor side
This view shows the second screw that holds the pump together. The two wires are connected to the high pressure end of the pump cartridge.

The "L" shaped rod holds the "low fuel" sensor onto the assembly.

Pump regulator side

This view shows the complete pump the way it would normally be mounted onto the Suzuki fuel tank.

The white clamp is holding the low pressure regulator onto the filter. Since the fuel tank is located at the back of my car I use a remote regulator near the engine to insure that the correct fuel pressure is presented to the injectors.
Pump terminals

These three wires have to be disconnected before disassembling the pump.

The black item is the high pressure fuel filter. This filter is not used with my modification. I use a normal high pressure fuel filter mounted at the engine.

The small round item at the end of the filter is the fuel pressure regulator which won't be used either.
Pump diassembled

Here is what all the parts look like after the two screws are removed (laying on the left and right side of the pump cartridge) and the pump is pulled off the support metal.

The tan item located at the top of the pump is the intake filter which was inside the dome.

The small items to the lower left are the low fuel level sensor parts. They are not used.
Pump cartridge dissasembled

Finally the pump cartridge is free where you can really see what it looks like. The output pipe is located behind the power input wires.

There is an O ring on the output pipe that is inserted into the filter (on the right). This O ring tightly holds the parts together and makes it very difficult to remove the pump from the filter.

I had to use two flat bladed screw drivers to gently pry the pieces apart.
Pump side view

The actual pump cartridge is ~6" long by ~1-1/2" in diameter.

The intake filter is clearly shown in this view. When finally mounted in the tank the bottom of the filter should just clear the bottom of the fuel cell.

I don't want the filter to touch the bottom of the tank to prevent vibration or movement to wear the filter or tank away.

Pump top

This view shows the output end of the pump.

The two wires are the battery + and battery - (ground) supply wires to the pump. The wires pass through a cover which protects the terminals from any stray metal particles. The wires will have to be replaced by longer wires.

The round tube at the top of the picture is the high pressure outlet pipe. The high pressure relief outlet is located under the wire cover.
Pump vs MPV

Here is a comparison of the Suzuki pump and the MPV pump. The Mallory pump I was using is even larger than the MPV pump!

Since the Suzuki pump is the original one that was used with my engine I've had no problem with it not supplying enough fuel.

Now that we have the pump apart we can finally start making the fuel pump mount.
(But first!)
Pump filler

This picture is presented out of sequence to help clarify how the mount is attached to the fuel cell. This picture is the fuel cell filler opening. The top of the picture faces the front of the car. You can see some of the foam that is inside the tank to help prevent the fuel from sloshing around.

The vertical item inside the tank is the top end of the fuel pump mount. It is a 10" length of 1" x 1 x 1/10" thick 90 aluminum. The vertical angle ends about 1" above the bottom of the tank. The fuel pump is attached to the lower end of the angle. The fuel pump is mounted so that the pick up screen just clears the bottom of the tank.

The angle is actually shiny aluminum but it appears black in this picture. The shiny hose next to the angle is the 3/8" ID stainless steel braided fuel line connected between the pump and the tank output fitting.

The top end of the vertical angle is attached to a 3" length of horizontal 1" x 1" x 1/8" thick 90 piece of aluminum. The horizontal angle is rounded to match the curvature of the metal ring. The top two bolts mount the horizontal angle to the inside of the tank.

Planning your mounting bracket:

You will have to measure your fuel cell/tank etc to make the aluminum parts match the dimensions of your fuel tank/cell. The first thing to do is to drain the fuel out of the tank. I then removed the filler assembly. I can easily get my arm into the tank through the ~4" diameter hole.

Gas fumes can irritate your skin. The way I solve that problem is to take an old sock and cut the toe off. I then slip that over my arm so the rough edge of the tank doesn't scratch my skin. I then take a plastic bag that my newspaper is delivered in and cut the closed end off. I slip the plastic bag over my arm and use a rubber band to seal the bag around my wrist. The fumes don't seem to bother my hand. I now use a latex mechanics type glove on my hand to make sure though.  I put the plastic bag on last so it's easier to take off between gas tank diving episodes.

Once you know how deep your tank is and the positions of the filler mounting screws etc you can plan the mounting brackets. In my case I did an AutoCad drawing of the top view of the tank and I was able to determine that the pump and the mounting bracket would fit between the two forward filler mounting screws and the forward inside edge of the fuel cell.

Since the tank is tilted towards the front of the car the front of the tank is lower than the back. The pump is positioned at the front edge of the tank to pick up the fuel.

The mounting bracket:

The next series of pictures will show how the two pieces of aluminum are connected and how all the parts relate to each other.
Pump mount back

This picture shows the side of the mount that ends up facing the rear of the car and the two pieces of aluminum mentioned in the previous picture. The left side of the mount will be upward when mounted.

You can see the curve I cut/filed in the 3" long piece of aluminum that fits around the filler parts at the top of the fuel cell. If you look carefully just below the curved cutout you will see the two 1/4" diameter holes that the filler mounting bolts go through to hold the mounting bracket to the underside of the filler.

The two aluminum pieces are held together with two round head 1/4" - 20 bolts using Nylon insert captive nuts.

The pump is held onto the bottom of the longer piece of aluminum by a hose clamp.

The high pressure hose is a ~14" length of 3/8" ID stainless steel braided fuel/oil line. A hose clamp is used at each end of the hose.
Pump mount back

This view shows the "front" side of the pump mount. The black cushioning material under the hose clamp is a rubber like strip from the MPV fuel pump mount.

The pump and hose clamp in this view are positioned towards the front of the car when installed in the fuel cell. The pump just clears the inside edge of the wall of the fuel cell.

Remember, ALL items you use inside the fuel cell/tank MUST be able to resist fuel!

If you use the wrong type of material it will most likely dissolve in the fuel and may end up clogging your injectors etc with sludge.

I used Teflon insulated wires to bring the battery voltage to the pump. They are covered with short pieces of spiral nylon (from the MPV) to keep them from rubbing on nearby metal parts. The wires are held to the aluminum by nylon tie wraps.
Mount completesuzuki-c2-mount-done.jpg

Here is the finished pump mount in all it's glory.

The solid 3/8" OD pipe on the end of the flexible hose connects to the output fuel fitting at the top of the tank (next picture). I used a rather long flexible hose so it could be positioned to clear the fuel level float.

By the way, bending a piece of 3/8" stainless pipe isn't easy. I used a 3" diameter "V" belt pulley as a form to bend the pipe around. I clamped the pulley horizontally in my bench vise, inserted the pipe into the V gap and gently bent it around the pulley. It has a slight crimp in it but it's not too bad considering the tight bend I made.

The electrical connector on the end of the Teflon wires is from the MPV and connects to the inside end of the electrical fitting on the top of the tank. This fitting was made by cutting out a 3" diameter  portion of the MPV pump mount where the fitting was located. I also used the outside of the tank MPV wiring harness (next picture) so I had a matching electrical disconnect at the tank.

The RED wire connects to the "+" terminal on the pump and the BLK wire connects to the "-" terminal. Make sure you don't cross the polarities of the voltage when wiring the pump. All the pumps I've looked at have "+" and "-" cast into the plastic near the terminals.

Mounting the pump in the fuel cell:

The opening in the fuel cell is large enough so all the parts slipped through the hole with no problem.

I carefully measured and positioned the pump so the inlet filter screen clears the bottom of the tank by 1/8" or slightly less.

To finish the installation, I installed the two bolts through the horizontal mounting bracket and a large plastic ring which is part of the filler cap itself. The ring is located inside the fuel cell between the new pump mounting bracket and the top of the fuel cell. Don't mount the exterior metal part of the filler cap at this time. I used wing nuts and flat washers to temporarily hold the parts in position in the fuel cell.

I then connected up the pump outlet hose to the inside of the fuel line fitting that goes to the pressure regulator at the front of the car. Check that the fuel line doesn't interfere with the fuel level float arm.

Next connect the supply voltage connector to the inside of the  "voltage to pump" connector. It may be be easier for you to do the electrical connection first.

Do not run the pump without fuel in the tank. The fuel actually lubricates the pump motor bearings.

Before connecting supply voltage connector to the fuel tank, I used a voltmeter to double check that I had the polarity correct at the mating wiring connector that is part of the car wiring. Once I knew the polarity was correct I plugged in the fuel pump supply voltage connector, put some gas in the tank and checked the system for leaks and fuel pressure.

It took a few ON/OFF turns of the key to get the air purged from the system but once the pressure remained steady when the switch was OFF I was ready to start the car.

Obviously it didn't blow up because I am writing this article.  I did have the fire extinguisher handy just in case ............

I then finished assembling the remaining filler cap hardware.

Time to take a test ride!
But first (again)!
Fuel cell top

The final product:

Starting from the lower left and going clockwise:
The "Check valve" is used to make sure that if the car flips or the return fuel line is cut, that fuel can't drain out of the tank. The original motorcycle battery disconnect on falling over switch is used to remove all battery power if the car flips.

The "Return fuel line" is the connection where fuel flows back into the tank from the pressure regulator mounted near the engine. A pipe inside the tank extends downward to within 2" of the bottom of the tank and ends up in the foam packing. The pipe actually helps to hold the foam in place.

The "Vent hose" is the connecting hose from the "Fuel cell vent" to the "2 way valve".

The "2 way valve" is the (take a guess)  2 way valve from a Honda CRX. It allows a slight pressure to build up in the tank (one way) yet allows the tank to draw in fresh air with no restriction (the other way).  This tends to reduce the amount of fuel evaporation and holds more fumes inside the tank rather than allowing them to be stored in the charcoal canister.

The "Differential vent" is a flexible hose to a filter mounted under the top frame tube. Ever have water sucked into your (car's) rear end when going through a "small" puddle after a hurricane? The axle cools down and water can get sucked into it through the normal short vent.

WHAT! You drive your Locost when there's water on the road!    =:0

The "Fuel cell vent" is built into the filler cap. See the article "Does your garage smell of gas after a ride?" for details of how to allow the fuel cell to vent properly and get rid of gas smells in your garage.

The "Fuel gage wiring" is the JC Whitney universal fuel level item and is leak proof.

The "Fuel line to regulator" is the pressurized fuel line from the fuel pump to the fuel pressure regulator at the front of the car.

The "Voltage to pump" is the cut down MPV connector mount. This supplies the voltage to the pump and is leak proof.

The two electrical feed through mounting plates have matching 3/8" thick aluminum rings inside the tank to provide a solid surface to run the 1" long countersunk screws through. I used nylon insert lock nuts on all the fittings.

OK, guys now it's your turn to make a pump mount. Have fun and be careful.

Additional thoughts:

If you are building your own fuel tank and are planing on using a large filler similar to what I have, I would design the pump holder such that it is welded to the bottom of the tank and use the hose clamp to fasten the pump to the mount.

After I run the first tank of gas through the pump with this new mount I plan on checking the hose clamp to make sure it hasn't loosened up in case the cushioning strip softens somewhat from being back in the fuel.