Spreadsheet for wiring K series engine into MG Midget or MGB
| Paul Walbran Motors: Wiring notes, K series engine & ECU intalled into MG Midget | |||||||||||||||
| (This was done for a VVC, but is generally applicable to non-VVC which is the same except for the VVC-specific sensors and functions) | |||||||||||||||
| Note: For this project, we used a standard MGF VVC ECU, the alarm ECU originally fitted to the same car as the donor engine ECU, the engine loom from an MGF, | |||||||||||||||
| and the matching plugs from the main loom of an MGF which connected it to the engine loom. We also used the diagnostic socket from the donor main loom. | |||||||||||||||
| The main ECU plugs are of the early 36 pin type | |||||||||||||||
| Part 1 of this spreadsheet attempts to diagramatically show the layout of where the various componets branch off the looms | |||||||||||||||
| Part 2 lists the functions of the various individual wires and includes some additional tips and comments | |||||||||||||||
| Part 3 is the business end – it is the list of connections to make in order to blend the VVC loom to the original MG loom. You may like to skip the explanations and go straight to the connection summary in this section | |||||||||||||||
| (Although developed for a Midget, it should apply equally to the MGB as the components and colour codes were largely common to both) | |||||||||||||||
| Any advice on errors in/improvements to this spreadsheet are welcome! | |||||||||||||||
| Part 1: Schematic layout of main electrical components/connections | Engine connections | ||||||||||||||
| Main relay pack (2 plugs, large & small) | Black Plug | Blue Plug | Individual connections | ||||||||||||
| ECU plugs (VVC:2×36 pin plugs; non-VVC: 1×36 pin plug) | (Connections to the rest of the car) | ||||||||||||||
| Part 2: What the wires do | |||||||||||||||
| Wire no | (as arbitrarily identified by me in drawing this list up) | ||||||||||||||
| 1. Wires from the ECU plugs: | |||||||||||||||
| (a) Wires going between the ECU and the engine sensors (refer also 1 (e) below) | |||||||||||||||
| wire | connects to | Notes | |||||||||||||
| 1 | Yellow/purple | Map sensor | |||||||||||||
| 2 | Red green | ” “ | |||||||||||||
| 3 | green brown | inlet air temp sensor | |||||||||||||
| 4 | green/orange | oil temperature sensor | |||||||||||||
| 5 | pink/green | coolant temperature sensor | |||||||||||||
| 6 | yellow/green | throttle sensor | |||||||||||||
| 7 | yellow/purple | ” “ | |||||||||||||
| 8 | red/yellow | camshaft position sensor | |||||||||||||
| 9 | black/blue | ” ” “ | |||||||||||||
| 10 | blue/purple | crankshaft postion sensor | |||||||||||||
| 11 | white/blue | ” ” “ | |||||||||||||
| 12 | slate | Oxygen sensor | |||||||||||||
| 13 | light green/slate | ” “ | |||||||||||||
| (b) Wires going from the ECU to engine functions | |||||||||||||||
| wire | connects to | ||||||||||||||
| 14 | orange/slate | stepper motor (idle air control valve) | |||||||||||||
| 15 | pink/blue | ” “ | |||||||||||||
| 16 | orange blue | ” “ | |||||||||||||
| 17 | orange green | ” “ | |||||||||||||
| 18 | yellow/brown | No 1 injector | |||||||||||||
| 19 | yellow/red | No 2 injector | |||||||||||||
| 20 | yellow/white | No 3 injector | |||||||||||||
| 21 | yellow/black | No 4 injector | |||||||||||||
| 22 | white/black | ignition coil 1 | |||||||||||||
| 23 | white/black | ignition coil 1 | |||||||||||||
| 24 | black/brown | VVC solenoid – increase | |||||||||||||
| 25 | black/yellow | VVC solenoid – decrease | |||||||||||||
| (c) Wires going from the ECU to the main relay pack | |||||||||||||||
| wire | connects to | function | |||||||||||||
| 26 | black/green | small plug | oxygen sensor | ||||||||||||
| 27 | white/pink | small plug | security link? Activates ECU power-on relay | ||||||||||||
| 28 | black purple | small plug | security link? Activates fuel pump relay | ||||||||||||
| (d) Power input wires | |||||||||||||||
| wire | function | ||||||||||||||
| 29 | brown/pink (1) | 12 volt input to all functions, switched on by ECU power-on relay in the main relay pack. | |||||||||||||
| The power-on relay feeds via brown/pink to an internal junction in the loom, thence feeds 12V to | |||||||||||||||
| 29a | ECU | ||||||||||||||
| 29b | purge valve, with wire 40 – not required, (can be blanked off or the plug can simply be left free on its short piece of wire) | ||||||||||||||
| 29c | stepper motor (idle air control valve) | ||||||||||||||
| 29d | speedo transducer (where fitted) – this can be blanked off | ||||||||||||||
| 29e | VVC solenoid valve – increase | ||||||||||||||
| 29f | VVC solenoid valve – decrease | ||||||||||||||
| 29g | coil pack. | If running an original early MGB/Midget electric tacho (loop type), locate and disconnect this wire at the junction | |||||||||||||
| (make sure you have the coil pack feed, not something else!!) | |||||||||||||||
| The disconnected wire is then connected to the Midget’s original coil feed wire, and hey presto! the tacho works! | |||||||||||||||
| (See note at the end for how we did it) | |||||||||||||||
| Don’t cut this wire if you have the later voltage sensing tacho, (identified by a single white/black signal feed | |||||||||||||||
| wire on the back of the tacho – in addition to the green power feed – rather than a white wire which goes through a loop). | |||||||||||||||
| 29h | Brown/pink (2) | Injectors | this one comes direct from the relay pack, not via the above junction. (Same wire as 54 below, I counted it twice) | ||||||||||||
| (refer (2) below) | |||||||||||||||
| (e) common between ECU and sensors: | |||||||||||||||
| wire | function | ||||||||||||||
| 30 | pink/black. | This wire connects to an in-loom junction, thence to: | |||||||||||||
| 30a | Map sensor | ||||||||||||||
| 30b | inlet air temp sensor | ||||||||||||||
| 30c | oil temperature sensor | ||||||||||||||
| 30d | coolant temperature sensor | ||||||||||||||
| 30e | throttle sensor | ||||||||||||||
| 30f | also joins to the engine bay temperature sensor | ||||||||||||||
| (This sensor is on the MGF bodywork, not the engine, so this wire doesn’t go to the engine, but to one of the other plugs – refer (3) below) | |||||||||||||||
| (f) Wires from the ECU to functions external of the engine (in the engine bay or elsewhere) | |||||||||||||||
| wire | connects via | function | Retain or blank off? | Comments | |||||||||||
| 31 | yellow/red | blue plug | Alarm ECU | retain | carries the coded security link between the two ECU’s | ||||||||||
| 32 | black (4 wires) | direct connection | Earth connections | retain | Most ECU functions, and some (but not all) of the sensors work by completing a circuit to earth | ||||||||||
| 33 | pink | black plug | diagnostic socket | retain | A useful socket to get and retain with the system | ||||||||||
| 34 | blue/slate | black plug | cooling fan (1) 102 dec C | retain | Only one fan required, but keep both wires for actuate a fan relay in case I mixed them up! | ||||||||||
| 35 | blue/yellow | black plug?? | cooling fan (2) 108 deg C | retain – just in case! | (Note: As the ECU earths these wires, join them to the earth terminal of the relay primary.) | ||||||||||
| 36 | slate/white | black plug | engine bay temperature | blank off | (As in 1(e), #30f above. This sensor is on the MGF bodywork, not the engine, so | ||||||||||
| 30f | pink/black | black plug | ” ” “ | blank off | these wires don’t go to the engine, but to one of the other plugs – refer (3) below) | ||||||||||
| 37 | blue/red | black plug | air conditioning | blank off | |||||||||||
| 38 | blue/green | black plug | air conditioning | blank off | |||||||||||
| 39 | blue/black | black plug | air conditioning | blank off | |||||||||||
| 40 | yellow/orange | own plug | purge valve | blank off | can be blanked off or the plug can simply be left free on its short piece of wire | ||||||||||
| 41 | slate/blue | blue plug | air conditioning | blank off | |||||||||||
| 42 | green/red | blue plug | instrument pack | blank off | |||||||||||
| 43 | brown/black | blue plug | MGF engine bay cooling fan | blank off | |||||||||||
| 44 | white/black | blue plug | instrument pack, MGF tacho | blank off, OR …. | Connect to the later B/Midget Smiths voltage sensing tacho | ||||||||||
| (This later tacho is identified by a single whit/black signal feed, | |||||||||||||||
| rather than a white wire running through a loop. | |||||||||||||||
| If you have this later tacho, don’t cut the brown pink feed wire to the coil! | |||||||||||||||
| 2. Wires from the Main Relay Pack: | |||||||||||||||
| (a) Wires connected to the relay pack via the small plug on the back of it | |||||||||||||||
| wire | goes to/comes from | via | function | retain or blank off? | Comments | ||||||||||
| 45 | White | Ignition sw via fuse box | blue plug | switched 12V to actuate fuel pump relay | retain | join to fuse box where other white wires connect | |||||||||
| 46 | white/red | ign sw (starter position) | blue plug | starter relay actuation | retain | join to white/red in Midget loom | |||||||||
| 47 | black/white | Alarm ECU | blue plug | Imobiliser link to starter relay | retain | ||||||||||
| 28 | black/purple | ECU | engine loom | Completes fuel pump activation | retain | ||||||||||
| 27 | white/pink | ECU | engine loom | Activates ECU power-on relay | retain | ||||||||||
| 26 | black/green | ECU | engine loom | oxygen sensor actuation | retain | ||||||||||
| (b) Wires connected to the relay pack via the large plug on the back of it | |||||||||||||||
| 48 | brown, thick (1) | Fuse box, 30A fuse | own plug | 12V to ECU power-on relay | retain | These two are separate wires coming from separate fuses. | |||||||||
| 49 | brown, thick (2) | Fuse box, 30A fuse | same plug | 12V via relay to: | oxygen sensor heater | retain | I used an additional fuse box to service them | ||||||||
| starter solenoid | retain | (Part no 606253A, the common early BMC fuse box) | |||||||||||||
| 50 | brown/slate | Inertia Switch | blue plug | 12V supply to: | fuel pump, via relay | retain | The other side of inertia switch is fed from | ||||||||
| same fuse as brown (1) above, via a brown wire | |||||||||||||||
| The inertia switch is mounted on the body, not the engine. | |||||||||||||||
| 51 | brown/red | starter solenoid | engine loom | retain | |||||||||||
| 52 | white/purple | fuel pump | black plug | main feed to fuel pump | retain | join to white fuel pump wire in Midget rear loom. | |||||||||
| 53 | blue/red (thick) | oxygen sensor heater | engine loom | retain | |||||||||||
| 29 | brown/pink (1) | junction inside engine loom | 12V supply as listed in 1(d) above | retain | |||||||||||
| 54 | brown/pink (2) | injectors | engine loom | 12V supply for injectors | retain | (Same wire as 29h above, I counted it twice) | |||||||||
| 3. Other engine functions connecting to the engine bay: | |||||||||||||||
| wire | goes to/comes from | via | function | retain or blank off? | Comments | ||||||||||
| 55 | brown/yellow | Alternator | blue plug | exciter wire | retain | connect to brown/yellow in Midget loom | |||||||||
| 56 | brown (very heavy) | Altenator | direct | main feed | retain | connect to main power terminal (battery, battery feed) | |||||||||
| 57 | red (thick-ish) | Air conditioning | black plug | a/c clutch | blank off | OR use for power feed to coil pack for loop-type tacho fitted (see note below) | |||||||||
| 58 | green/blue | unknown | blue plug | Couldn’t work this one out. | blank off! | The car works fine without it! (Temp gauge possibly) | |||||||||
| 59 | green/yellow | reverse light switch | blue plug | reverse lights | retain | connect to green wire end of fuse in main fuse box | |||||||||
| 60 | green/brown | reverse light switch | blue plug | reverse lights | retain | connect to green/brown in rear loom | |||||||||
| 61 | white/brown | oil pressure switch | black plug | oil pressure warning light | retain | retained for possible use (we connected the original pressure gauge) | |||||||||
| 62 | brown/blue | oil temperature sensor | black plug | oil temp gauge | retain | retained for possible use (we connected the original pressure gauge) | |||||||||
| Part 3: What to connect | |||||||||||||||
| 1. Summary | |||||||||||||||
| Connect these | |||||||||||||||
| wire | goes to/comes from | via | function | Connect to | |||||||||||
| black/white | Alarm ECU | (Imobiliser link to starter relay) | Alarm ECU | ||||||||||||
| blue/slate | ECU to cooling fan (1), 102 dec C | (fan-on signal) | Earth side of actuating coil of new fan relay | ||||||||||||
| brown/slate | Inertia Switch | (cuts fuel pressure in event of accident) | Inertia Switch. The other side of inertia switch is fed from the fuse box | ||||||||||||
| brown/yellow | Alternator | (exciter wire) | brown/yellow in Midget loom, goes to warning light | ||||||||||||
| White | Ignition sense wire | (ign switched 12V to actuate main relay) | fuse box where other white wires connect | ||||||||||||
| white/purple | fuel pump | (main feed to fuel pump) | join to white fuel pump wire in Midget rear loom. | ||||||||||||
| white/red | ign sw (starter position) | (starter relay actuation) | white/red in Midget loom | ||||||||||||
| yellow/red | ECU to Alarm ECU | (coded signal to & from alarm unit) | Alarm ECU | ||||||||||||
| plus: | |||||||||||||||
| brown (very heavy) | Altenator | (main charging circuit conenction) | connect to main powr terminal (battery, battery feed) | ||||||||||||
| black (4 wires) | ECU to Earth connections | earth (make sure it is a good one!) | |||||||||||||
| brown, thick (1) | Fuse box, 30A fuse | on own plug | 12V supply to the ECU & harness | New fuse box | |||||||||||
| brown, thick (2) | Fuse box, 30A fuse | same plug | 12V supply to oxygen sensor heater | New fuse box | |||||||||||
| (these two 12 V supplies both go via the main relay pack where they are switched on and off by the white ignition sense wire) | |||||||||||||||
| Optional connections | |||||||||||||||
| blue/yellow | ECU to cooling fan (2) 108 deg C | run to fan relay as a stand-by, but don’t connect | |||||||||||||
| brown/blue | oil temperature sensor | (oil temp gauge) | carry through to dash for actual or potential oil temp gauge | ||||||||||||
| green/brown | reverse light switch | (reverse lights) | green/brown in Midget rear loom | ||||||||||||
| green/yellow | reverse light switch | (reverse lights) | green wire end of fuse in main fuse box | ||||||||||||
| pink | ECU to diagnostic socket | Rover diagnostic socket | |||||||||||||
| white/black | Tacho connection | Connect directly for RVC voltage-sensing type tacho, for loop type see note at the bottom of this spreadsheet | |||||||||||||
| white/brown | oil pressure switch | (oil pressure warning light) | carry through to behind dash for actual or potential oil pressure light | ||||||||||||
| (Note re reverse lights: connecting as above eliminates the need for separate connections for the reverse lights, but retaining these as original won’t affect anything) | |||||||||||||||
| Don’t need | |||||||||||||||
| blue/black | |||||||||||||||
| blue/green | |||||||||||||||
| blue/red | |||||||||||||||
| brown/black | |||||||||||||||
| green/red | |||||||||||||||
| pink/black | |||||||||||||||
| red (thick-ish) | but may be needed for loop-type tacho – see note at the bottom of this spreadsheet | ||||||||||||||
| slate/blue | |||||||||||||||
| slate/white | |||||||||||||||
| green/blue | |||||||||||||||
| yellow/orange | (purge valve, on a separate plug) | ||||||||||||||
| 2. Plug-by-plug version of the above | |||||||||||||||
| (Note: The wire no’s below are the same as those in part 2 above to aid in cross-referencing if you want to) | |||||||||||||||
| (a) Black Plug | |||||||||||||||
| wire | goes to/comes from | via | function | retain or blank off? | Connect to | ||||||||||
| List sorted by wire clolour | |||||||||||||||
| 39 | blue/black | ECU to air conditioning | blank off | ||||||||||||
| 38 | blue/green | ECU to air conditioning | blank off | ||||||||||||
| 37 | blue/red | ECU to air conditioning | blank off | ||||||||||||
| 34 | blue/slate | ECU to cooling fan (1) 102 dec C | retain | Earth side of actuating coil of new fan relay | |||||||||||
| 62 | brown/blue | oil temperature sensor | oil temp gauge | retain | carry through to dash for actual or potential oil temp gauge | ||||||||||
| 33 | pink | ECU to diagnostic socket | retain | Rover diagnostic socket | |||||||||||
| 30f | pink/black | ECU to ” ” “ | blank off | ||||||||||||
| 57 | red (thick-ish) | Air conditioning | a/c clutch | blank off | OR use for power feed to coil pack for loop-type tacho fitted (see note below) | ||||||||||
| 36 | slate/white | ECU to engine bay temperature | blank off | ||||||||||||
| 61 | white/brown | oil pressure switch | oil pressure warning light | retain | carry through to behind dash for actual or potential oil pressure light | ||||||||||
| 52 | white/purple | fuel pump | main feed to fuel pump | retain | join to white fuel pump wire in Midget rear loom. | ||||||||||
| 35 | blue/yellow | ECU to cooling fan (2) 108 deg C | black plug?? | retain – just in case! | run to fan relay as a stand-by, but don’t connect | ||||||||||
| (b) Blue Plug | |||||||||||||||
| List sorted by wire clolour | |||||||||||||||
| 47 | black/white | Alarm ECU | Imobiliser link to starter relay | retain | Alarm ECU | ||||||||||
| 43 | brown/black | ECU to MGF engine bay cooling fan | blank off | ||||||||||||
| 50 | brown/slate | Inertia Switch | 12V supply to: | fuel pump, via relay | retain | Inertia Switch. The other side of inertia switch is fed from | |||||||||
| same fuse as brown (1) above, via a brown wire | |||||||||||||||
| 55 | brown/yellow | Alternator | exciter wire | retain | brown/yellow in Midget loom, goes to warning light | ||||||||||
| 58 | green/blue | unknown | blank off! | ||||||||||||
| 60 | green/brown | reverse light switch | reverse lights | retain | green/brown in Midget rear loom | ||||||||||
| 42 | green/red | ECU to instrument pack | blank off | ||||||||||||
| 59 | green/yellow | reverse light switch | reverse lights | retain | green wire end of fuse in main fuse box | ||||||||||
| 41 | slate/blue | ECU to air conditioning | blank off | ||||||||||||
| 45 | White | Ignition sw via fuse box | switched 12V to actuate fuel pump relay | retain | fuse box where other white wires connect | ||||||||||
| 44 | white/black | ECU to instrument pack | blank off, OR …. | use this one as the link between tacho and the coil pack feed. | |||||||||||
| (Refer detail above.) | |||||||||||||||
| 46 | white/red | ign sw (starter position) | starter relay actuation | retain | white/red in Midget loom | ||||||||||
| 31 | yellow/red | ECU to Alarm ECU | retain | Alarm ECU | |||||||||||
| (c) Direct connection | |||||||||||||||
| 56 | brown (very heavy) | Altenator | main feed | retain | connect to main powr terminal (battery, battery feed) | ||||||||||
| 32 | black (4 wires) | ECU to Earth connections | retain | earth (make sure it is a good one!) | |||||||||||
| (d) Other plugs | |||||||||||||||
| 48 | brown, thick (1) | Fuse box, 30A fuse | own plug | 12V to ECU power-on relay | retain | New fuse box, as above | |||||||||
| 49 | brown, thick (2) | Fuse box, 30A fuse | same plug | 12V via relay to: | oxygen sensor heater | retain | New fuse box, as above | ||||||||
| 40 | yellow/orange | ECU to purge valve | own plug | blank off | can be blanked off or the plug can simply be left free on its short piece of wire | ||||||||||
| NOTE | Connection for loop-type tacho | ||||||||||||||
| This tacho senses the current fluctuations in the primary circuit of the coil. | |||||||||||||||
| The original circuit goes: | |||||||||||||||
| Ignition switch – (white wire) => tacho loop – (still a white wire) => engine bay => coil +ve | |||||||||||||||
| We connected this original coil feed wire to the black plug, wire 57 – which was originally the red air conditioning clutch wire. | |||||||||||||||
| This red wire follows the same path within the engine loom as the coil pack brown/pink wire, making it easy to divert to this new function, and is also of a suitable size. | |||||||||||||||
| Inside the engine loom, we connected this red wire to the coil pack’s brown/pink wire, which was separated from the junction in 29(g) above | |||||||||||||||
| (It’s not the right colour, but it’s simply available in the plug and is the right size) | |||||||||||||||
| Although we made this connection in the middle of the loom by the multi-brown-pink junction, we worked out in the end that we could more simple have made this by | |||||||||||||||
| joining much closer to the coil pack, or even by diverting the red directly to the coil pack and fiting a new mini-spade to it. | |||||||||||||||
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