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How to Install a Bosch 040 fuel pump into S13.
Including wiring upgrade.
In this guide I will be covering the install of the ever popular Bosch 040 fuel pump and how to rewire it straight from the
battery. First I will be covering how to install the pump itself into the tank and then the wiring separately as these can be done
at different times as I did.
Pump Install
Parts Needed :
EFI intank fuel hose ID - 8mm – 1 meter
EFI hose clamps x 2
6mm nuts x 2
5mm nuts x 2
Ring crimp connectors x 2
Length of 15 amp red wire x 1 meter
Length of 15 amp black wire x 1 meter
Large hose clamps x 2
1. First we need to release the pressure in the fuel lines otherwise when you remove them fuel will spray everywhere – not
what we want!
Start by removing the fuel pump fuse which is located in the black fuse/relay box next to the battery. Next start the car - it
should stall within a few seconds, disconnect the battery negative lead and now we are ready to remove the standard
pump.
2. Access to the tank is in the boot on the driver’s side, pull back the carpet and you should something similar to this.
(Disregard the blue wire for now as it is explained later in the wiring install).
3. Undo the 4 bolts on the pump cover and the 2 screws on the connector cover to expose the pump cradle. You should now
see something like this.
Mine had copious amounts of dirt on top so you may want to clean it off so it won’t fall into the tank later. Next take note of the
two hoses come from the top, these must go back on the same way so mark one of them or remember which hose clamp
goes where. Remove the hose clamps and use a flat head Screwdriver to push the hoses off being careful not to damage
them. I found that some fuel spilt from the feed line even though I had depressurised the system. Next disconnect the wiring
connector and unscrew the 6 screws holding the cradle and remove it from the tank.
Note: There is a large O-ring that seals the cradle to the top of the tank which loves to expand making it very hard to get back
into position. Place it in the freezer as soon as you take it out and it won’t expand; this will make your job much easier.
4. You will now be confronted by the stock pump hanging from its cradle. Before you remove anything get out a ruler or a
tape measure and measure the distance from the top of the cradle to the pick-up point, this will give you the correct mounting
position for the new pump. Next undo the electrical connections and the hose clamps from the pump and slide it out from the
bottom.
5. Once the old pump has been removed the cradle needs to be modded before the new pump will fit. First I bent down the
bottom of the cradle flat because I wanted to have the option to return it to stock if I wanted to. Next the feed line will have to
be cut slightly as it is too long for the new pump. The amount I have marked in the pic is all that is needed.
6. Now the pump can be fitted to the cradle. Take the length of fuel hose and push it onto the top of the pump as far as you
can. I got my hose all the way down which was very difficult but I wanted to make sure it was going to be secure. Next put the
two hose clamps loosely onto the hose and push it on to the feed line of the cradle until the bottom of the pump is in the same
position of the stock pump.
7. Next we need to secure the pump to the cradle. This is where I got a little creative with my mounts, you can just use hose
clamps straight around the pump and the cradle but this approach can be very noisy so I decided to insulate mine. First I took
a length of fuel hose (220mm approx.) and sliced it down the middle lengthways then I slipped it around the inside of the
clamp. I used two clamps in this fashion to secure the pump making sure the insulation went around the back of the pump
and not the cradle. I found it a major pain to actually get them around the pump properly without the hose falling off but to
make it easier get larger clamps undo them all the way and wrap them around the pump and cradle first then attach them
back together. At this stage I also tightened the efi hose clamps and bent the end of the cradle back further so it would clear
the bottom of the tank and provide a failsafe for the lower clamp.
8. All that is left now is to do the electrical connections. I originally was going to use some 12 gauge wire rated for 25amps I
got from jaycar but I wasn’t sure if it could handle being in fuel so I asked my local auto electrician and he gave me some new
wire rated for 15amps, seeing as the pump is rated at 13amps this will be sufficient. (I will go into this further in the next
section).
Desolder the stock wires from the lugs at the top of the cradle and solder the new lengths on. Next crimp some ring
connectors to the new wires and solder them also to make sure (I also used some heat shrink). Connect the new ring
connectors to the terminals on the pump and use the correct nuts to secure them, 6mm for the positive and 5mm for the
negative. I used 2 nuts to make sure they would not come loose.
In this image you can see a better view of the insulated clamps.
9. Now it is time to put the cradle back into the tank. First take the O-ring out of the freezer and place it back into its seat, if
you’re lucky it will still be the same size. Putting the cradle back in is just the reverse of removal but just be careful of that Oring as I had a little trouble with it and it fell into the tank. Once you have it back in its just a matter of putting the bolts back in.
For the 6 bolts in the top of the cradle it’s very easy to strip the holes, so just do them up with a screwdriver or lightly with a
ratchet. Put the 4 bolts back into the cradle cover, connect up the plug, and screw on the plug cover and your done!
Thoughts.
Many of you with S13s have probably experienced hesitation on boost which can start to happen when the standard fuel
pump is getting old. I instantly noticed the hesitation had gone and the drive was smoother. As for the noise it is close to
inaudible inside the car, but when you are outside the car on the driver’s side it’s a little louder probably because there is less
material for the sound to pass through.
Wiring.
Although I was happy with the install I knew that the pump would not work to its full potential with the stock wiring as it is just
not made for it. I have made a diagram of what is needed, it’s very simple really. The relay is basically just a switch but
instead of having a button which you have to press it uses an electrical signal to switch on. Now that we have this we can
start to wire it up.
As you can see in the picture below the wires from the pump are a decent enough gauge, enough to handle 15amps but the
wires on the other side of the connector are thinner.
Parts needed:
Jaycar Cat number
12 gauge red wire – 5 meters 12 gauge inline blade fuse holder 20 amp blade fuse
SPST 30 amp horn relay
Horn relay base
Some heat shrink
Ring crimp connectors
WH3080
SZ2041
SF2138
SY4068
SY4069
First we need to run a heavy gauge wire straight from the battery. This is so there will not be much voltage drop over a long
distance. Disconnect the battery at this point if you haven’t already done so. If you have installed an amp into your car (I’m
sure most of you have) you would have done this before but for the people that haven’t I will try to explain it.
1. Find a suitable grommet in the firewall which we can run the wire through, on the S13 series this is just to the right of the
accelerator pedal. Take of the trimmings for the fuse box, scuff plate and the rear plastic trim (you will have to remove the
rear seat for this). Pull back the carpet and place the wire underneath the plastic cover with all the other stock wires, (it might
get a little tricky where the boot release is). Once you have the wire to the back seat, follow the wires going up the wheel arch
and through the small holes into the boot taping them together as you go.
Pic of the firewall grommet.
2. Now we need to mount the relay. Take off the trimmings around the driver’s side of the boot for easier access. I mounted
mine with the rear bolt in the metal box thingy (I’m not what it is!) under the speaker mount. As you can see I used a relay
harness to make it easier but spade crimp connectors will work as well.
3. Now it is time to connect the wires. The diagram below is what we will be following. First let’s connect the pump to the
relay. First locate the white wire with purple stripe (positive for the pump) and lengthen it using the same wire you used for the
pump and connect the other end to pin 30 of the relay (lower yellow wire in the pic). It would be a good time to cut the blue
wire with red stripe (negative for the pump), crimp a ring onto it and ground it to the cradle cover. Make sure you heat shrink
all your solder joints.
4. Remove the split tube from the stock wiring and locate the black wire with yellow stripe. This is the stock fuel pump positive
signal that we need to turn on our relay. Cut this wire and connect it to one of the white wires (I used pin 85). Next we need to
ground the other white wire to complete the circuit (pin 86). I used the bolt at the top of the pic as my ground because I did
not want to extend the wire, Attach a ring crimp connector and it’s done.
5. Last connection we need to make is to connect the red wire installed earlier to the relay. (Pin 87) Just solder them together
add some heat shrink and you’re done Make sure all the cut wires have been insulated with tape or heat shrink then neaten
up your install with some tape.
6. Lastly we need to connect the other end of the red wire to the battery. Connect the fuse holder to the wire and solder them
together. Next use large ring connector to attach it to the battery terminal. Try to use some split tubing to protect the wire a bit
more from the heat and tape/cable tie it out of the way.
7. Install the 20 amp fuse into the fuse holder and reconnect the negative terminal. Now you are ready to start the car!
Thoughts.
I notice an immediate difference in pretty much every way. The pump was now louder (not too much), but more importantly
the engine felt even more smooth and willing than before. I must say I am very happy with the way this has worked out.