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MG MGB GT V8 Factory Originals Technical - Hotwire EFi wiring question
My 3.9L Rover V8 has the Hotwire EFi on it.
My question is what wires do I use from the fuel injection wiring harness and what wires do I use from the existing MGB wiring harness to get the job done.
I'm trying to figure out how to wire every thing up to get the engine to run and I need some help. Can anybody help me out?
It would be much appreciated.
|Can you tell me what car you sourced the Efi harness from. I may be able to help you out.|
The whole works is out of an '89 Range Rover County. I have the ECU, the injection wiring harness, and the engine w/ Hotwire EFi. I just don't know which wire is what. Obviously the molded end parts go to certain parts on the fuel injection system. This I can figure out. But as far as gettig power to the harness, I'm lost. Thanks for any help.
|Basic Rover wiring colour codes apply.|
You should have a single 7 or 9 pin connector that doesn't have a home. The wires that come to this will be as follows...
Brown, white/slate, white/purple, black/yellow, black/orange, yellow, yellow/blue, brown/purple.
Some secondary colours vary with different model years and markets, but the basics will be the same.
The main connections are as follows...
Brown to main battery supply - permanently live.
White/slate to ignition switch for the 'ign on' signal.
White/purple feeds power to the fuel pump, but ensure that this then goes through an inertia swicth for safety.
The above are the main functions that apply to this connector. The others there are for ancillary functions as follows...
Black/yellow is the feed wire from the ECU to the dash warning light for EFi faults. Not an essential fit.
Yellow is the sensor wire to the ECU from the road speed input sensor. This assists the correct implementation of the idle speed, but is not that much of an issue if not fitted. However if the sensor IS fitted then the standard inbuilt speed limiter in the ECU will be active and kill the fuelling at between 110 and 112mph.
Black/orange is the sensor wire from the auto gearbox to indicate when the gearbox is in neutral and so the load on the engine is less. This is to enhance idle speed control and with a manual box is superflous.
Yellow/blus is the sensor wire from the air conditioning unit and again is an idle speed control function to ensure idle speed is maintained high enough when the aircon loads the engine and drags speed down. Not used unless your car retains aircon.
Both these latter two functions can be reallocated to other very heavy load functions that can drag the idle speed down and risk stalling.
Brown/purple is a function not used in the UK, but is going to be an additional sensor function for idle speed control.
In addition to the wires in this plug you will find a number of other connections. There are several separate earth connections. The ones nearest the injector end of the loom are intended to be bolted to the engine and not the body of the car. This is to allow for potential poorer earth paths from engine to body later in life. There will be additional earths nearest to the ECU plug end.
There are also a couple of standard relay holders which are for the main system relay and the fuel pump relay. You can see the colour codes of the wires from what I mention above.
A very important single wire connection that is separate and found near to the airflow meter plug is a single white/black wire which is the sensor connection wire for the negative side of the coil. This provides the ECU with engine speed information and has to be connected to the ECU through a 6.8k ohm resistor. This should actually be in the loom so a simple resistance check from the end of this wire to the ECU plug, pin 39 will reveal whether the resistor is in circuit. If not get one and use it to protect the ECU from spikes.
There will also be another couple of connectors. One should have a sealed resistor in it and is known as the 'tune resistor'. This alters the actual map in the ECU that is used.
There is also a diagnostic plug that should have four wires. Black/slate, white/light green, white/pink and white/yellow. Leave this untouched as it will alow for any Rover diagnostic unit to be plugged in and system faults read. Very useful if you have a problem that you can't get to the bottom of.
I expect that you should have perhaps two more unknown connections and if you note the colour codes of the wires and if they go to a particular pin of the ECU plug then I can identify them and see whether they should be used.
Oh and yes I have done a couple of injected V8 MGB's!!!
Thankyou very much. I was hoping you would see this thread and respond. I knew you had a "Hotwire" car and probably knew the wiring process.
I've also seen your "Federal version" MGB in "Tuning Rover V8 engines" and "How to give your MGB V8 power."
Thanks for the help.
I'll let you know about any other unknown connections when I get that far.
do the above instructions also apply to the older system as of 1980 sd1, the air flow meter system?
Also on page #51 of How to give your MGB v-8 power item #5 Two injection relays and a steering module (diode pack). Is this the same relays refered to in the Rover manual as convined relay? wired to the power resistor and then to the injectors.
One more thing what is a steering module or diode pack and where is it in the wiring diagram?
Yes. The early Airflow Meter system has an odd multi function relay with about 10 pins of different sizes and orientation. These match a couple of equally odd connectors. The later systems deleted this single complicated and costly item and broke it down to three parts, two standard 5 pin relays and one diode pack
The early multi function relay contains internal diodes to ensure that current flow has restricted paths. The later systems with the twin standard type relays has three diodes in the diode pack. The main function is to have a clean control of the fuel pump.
As you may know the ECU controls the operation of the fuel pump and once engine speed has dropped to betow I think about 400rpm the ECU reads this as a stalled engine. It then switches power off to the fuel pump relay. Clearly this is no good when trying to start the engine as cranking only gets the engine to about 275rpm. To overcome this a separate spur wire is taken from the starter and fed direct to the fuel pump relay through the diode pack. The pump then operated during cranking much like a ballast resisted coil.
thankyou very much for your help, I know now I have all parts for the fuel injection.
I enjoyed your detailed explaination of the Hotwire wiring diagram. One thing I don't understand is how the ECU knows when to inject the fuel into the individual intake ports. Am I right in assuming that the fuel is injected exactly when the intake valve is starting to open? Over the weekend I reread the fuel injection sections in both "How to Give your MGB V8 Power" and David Hardcastle's book on tuning the Rover V8 and couldn't find and explanation of the timing of the fuel charge.
the wiring diagram in the Rover manual for US sd-1 fuel injected cars 1980 the main harness connector to the convined relay and diodes pack shows a lead to ground (earth). this wire is not present in the actual connector in my car nor it is present in the connector to the fuel injection harness there are the 2 brown wires(battery), white/purple(inertia switch), white/red(start imput),white(ignition imput)but no black lead any idea why not?
Also my distributor is the lucas 35de8 fitted with a luminetion electronic ignition. my question is how do this changes the conections to the ballast resistor pictured on page 100 of the book How to give your MGB v-8 power. Do i still have to use the ballast resistor with the luminetion system?
Thank you for your help
The V8 in all injected forms to 1995 uses whats called 'banked injection' where all 4 injectors on one bank of cylinders are pulsed together. Only half the amount of fuel that is needed is injected at this time as one revolution later there is another pulse. As the 4 stroke cyle covers 720 degrees of crank rotation you see that by doing it this way means that not too much fuel gets the opportunity to condense on port walls when the inlet valve is closed. The post 1995 engines use sequential injection where each injector is times to pulse just as the inlet valve is opening.
The choice of ignition is makes no difference as you simply connect to the negative side of the coil and put the resister into the circuit to take the 'sting' out of the pulses.
The wiring! The pins on the relay should have numbers and pin 85 goes to earth. Locate this pin and check the continuity of any wire connected there. Additionally pins 5, 16, 17 and 35 from the ECU are connected to earth so double check these too.
|Rog, yes! i found pin #85 on the relay going to the fuel injection harness, not on the conector from the main wiring harness as the rover manual diagram indicates. I guess i was to forceful when i yanked the conectos from the relay, because, the tittle leg on the terminal was bent,and the black lead to ground(earth) was next to the other relays.|
I am a little obscure about the luminetion ignition. I know the 3 wire conector goes to the distributor, brown lead to negative on coil, black lead to earth. where does the red lead from the module connects to in the ballast resistor? and do i have to eliminate any of the 6 wires on the ballast resistor in order to connect the red lead?
Thank you again for all your help, and for taking the time to help us all MG v-8 fans
|Those of you using the SD-1 federal system but without the manual may find this site interesting- it has a wiring diagram for the system. in a Adobe Acrobat pdf format. Even though it is for the TR8, I found the wires and pins to be the same as the SD-1. |
The relay, by the way, is also used on 5 series BMWs. Mine was often intermittent and I sourced one at my local BMW repair shop new for about $60.
Are we talking about the Lucas Opus ignition from the SD1 here or the accessory market supplied Luminition system?
Your quite correct as all the V8 injection systems were the same across the model range for the same periods. So TR8 and SD1 up to 1982 are the same. SD1 1982 to 1985 were on their own and from 1985 to 1988 the Range Rover used the same system, except for the twin plenum late SD1. Even there the commonality of parts is considerable.
my distributor is the Lucas opus 35de8.
luminetion electonic module.
ballast resistor stock sd1.
|Romney, the colour codes do not match the original set up, and the addition of the 'Luminition' module adds confusion. I can't guid you where the specific wires go in this situation.|
Originally there were three wires into the ballast resistor, white/yellow which comes from the starter and provides full power to the ignition when the starter is operating. White which is the standard ignition switch controlled 12v power supply and a white/black wire that connects to the tacho and a diagnostic plug if fitted.
On the other side of the resistor is a white/green wire that goes to the + side of the coil, a red/black wire into the dizzy and a white/black that goes into the dizzy and to the negative side of the coil.
The connections on the ballast resistor are not even both sides. On the side that connects to the cars wiring the connections are evenly spaced along that side. There is a notch at the one end and the terminal at that end is the white/yellow wire. The middle connection the white and the other end the white/black.
On the other side you have two connections closer together with a noth between. Starting at the connection furthest away from the notch we have the white/green. The next (middle) connection is the red/black anbd the other end is the white/black.
These connections may not help much with your changed wiring.
This thread was discussed between 15/02/2000 and 05/03/2000
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