How To - fit UK spec 550cc Injectors/Resistor Pack to an Import Supra

There are two methods of performing this task. Below outlines the longer, but easier method. The other method involves changing the injectors with the manifold left in place. The latter method is quicker, but causes the most damage to your hands! Trust me I know! I will try to describe this method as best I can. Here.

Background Details

Import Supras all come with 440cc injectors as standard. There was never an option to fit the larger UK/US spec 550cc injectors so unless your car was modified previously it wont have 550cc injectors fitted. ALL UK spec Supras will have 550cc injectors fitted already. 

Step 1

• Nothing done yet
  

Step 2

• Aftermarket strut brace removed
• Throttle cable disconnected and tucked out of the way
• Disconnect multiplug from all the sensors on the intake manifold

Step 3

• The aftermarket FSE valve has been removed from it's mounting point and the vacuum hose disconnected
• Remove the top vacuum hose from it's banjo bolt and rotate out of the way
• Remove the vacuum hose from the side of the manifold
• There is a metal pipe framework mounted on the manifold. Unclip the diagnostic port from it, disconnect the hoses from either end, and unbolt from the manifold.
• Remove the vacuum hose from the rear of the intake manifold (not in picture)

Step 4

• Sensors Removed 

Step 5

• Disconnect boost sensor vacuum hoses from engine side of manifold
• Remove throttle cable bracket
• Remove cam cover breather hose
• Unbolt cold start mechanism from the rear of the intake manifold - you don't need to remove any hoses from it

Step 6

• Unbolt the power steering reservoir and wedge it out of the way towards the front of the car.
• Unbolt the throttle body from the intake manifold. There are two bolts on top and two nuts on studs underneath. The nuts are tricky to get at; you may need to temporarily remove the throttle stop bracket on the engine side to get at one of them.

Step 7

• Go from left to right and unbolt the seven bolts holding it in place, as shown in the 2nd picture
  

Step 8

• Manifold Removed

Step 9

• With a bit of maneuvering rearward, the manifold will now come away from everything else. You don't have to remove it completely from the engine bay, which is handy as otherwise you will have to remove heater hoses to the cold start mechanism, and then you are messing about with coolant.
• Remove the old throttle body and intake gaskets

Step 10

• At last you can now see the 440cc Injectors!

Step 11

• Here you can now clearly see the 440cc injectors, held in place by the three retainer brackets

Step 12

• Unplug the injector cables and move the injector wiring loom out of the way. the front injector (number 1) is fed from a separate cable and is also positioned 180 degrees round from the others due to this.
• Remove the retainer brackets. The rubber o rings on the back of the injectors will fall off quite easily, so watch out for that.

Step 13

Now its time to install the larger 550cc injectors

• In this picture you can see:
  The manifold wired back from the engine, just to keep it out of the way
• A G-clamp on the fuel return line to minimize spillage
  You will get some fuel go about the place when you perform the next step, so the usual safety nag about sparks, naked flames, etc. apply!
  
• Remove the 440cc injectors. Rotate them to aid in their removal. You will get some fuel flow, but not a great amount.

Before the 550cc injectors are fitted, it is important to trim the lugs off the 550's as the lugs are in a different location. These can be trimmed off with a Stanley knife. The modified injectors show the lugs trimmed off.

• Push in the 550cc injectors, again rotating to aid in this.

Step 14

• Once all six injectors are in, put on their rear o rings and refit the retainer brackets
• Clean up the four gasket surfaces
• Reverse the stripping procedure to rebuild.
• Double check all vacuum hoses, especially the one at the rear of the manifold.

Step 15

Now that the 550cc injectors have been fitted, its now time to fit the resistor pack.

Here is the entry point into the wiring loom

Step 16

• Unclip to loom's plastic bracket, and take it out
  

Step 17

• Unclip the plastic bracket and remove
• Unbolt the mounting bracket from the bulkhead and remove
• Unwrap the large amount of tape from the loom
• Carefully slit open the final layer of protection

Step 18

The wires I had to cut were Black with Orange stripes. Others have found them to be Black with White stripes. This may be because this car is pre 1996 facelift and the other was not (as far as I am aware).

A good pointer is the injector multiplug's. There are two wires going into each, and the common wire colour was black with an orange stripe. Using injector 6's plug, push a multi meter probe into the black and orange wire's socket. For the other probe, I used an old multi meter wire with a map pin on the end. You can just push this pin into the insulation of a wire in the loom and it will make a minimally invasive continuity check.

The black and orange wires all go to a common source, so continuity exists between all the injector plugs. Due to this, you only need a probe in one of the injector plugs to check the loom wires.

I found nine wires in the loom that were connected to the injectors. This was three too many, so I consulted the wiring diagram for the engine control system and found that the common source for the injectors led to multiplug IJ1. This connector lives in the passenger side kick panel. It connects the injector circuit to the rest of the car's electrical system.

Unplugging this isolated the injector circuit from anything else on the same source. Once I had done this, only six wires in the loom had continuity with the injector plug. Hurrah! I marked the wires with masking tape, as shown in the picture.

Step 19

The resistor pack for the 550cc injectors normally lives on the passenger side suspension turret, but my strut brace preludes this mounting point. I found a couple of unused holes in roughly the right place on the drivers side near the bulkhead. The mounting pictured is very solid and secure.

Its possible to get two types of resistor pack, the Toyota one shown in the picture, or an "after market" version - which I have. This bit still applies to either type.

You have to make up a cable to go from the resistor pack to the wiring loom. This involves cutting off the stock multiplug on the resistor pack and plumbing in your own plug. The cabling needs to be seven-core automotive, which has six coloured wires and one white one that is a thicker gauge.

The white wire coming out of the resistor pack connects to the white thicker gauge wire in the cable. The six black wires go to the thinner coloured wires. It doesn't matter which one connects to which wire.

Step 20

Here you can see the other end of the cable that goes off to the resistor pack. I chose to have another multiplug at this end to make it a bit neater.

Step 21

Here you can see the short stretch of automotive cable I used to make the loom end's connector to the resistor pack. Now, the wires have been cut in the wiring loom (yes, I did stress a lot at this part!). The right hand side of the wires will be connected to each other, and the white wire on the automotive seven-core cable. The left hand side of the wires are connected to the six coloured wires. It doesn't matter which wires go to which.

Step 22

Here you can see the coloured wires connected to the left hand side of the cut black and orange loom wires, and the soldering monstrosity that is the common connection on the right.

Step 23

Everything gets masked up here. Make sure all the soldered connections are well insulated (I eventually went for insulating tape rather than the heat shrink cable)

Step 24

The wiring loom is a bit fatter than it used to be, thanks to all that soldering, but it still fits in it's original bracket. I really went to town with the insulating tape, as I didn't want any spurious shorts later in the day.

You can see the cable tucked nicely out of the way, running along the bulkhead. It's tie-tagged in place quite securely.