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MG MGB GT V8 Factory Originals Technical - Newbie question - EFI, ECM

I'm thinking about an engine conversion (haven't even settled on the engine) and I'm curious how you go about installing a modern computer controlled/fuel injected engine into an old harness. Is it something where where's just a jump from the white ignition wire to run the computer from the donor, or do you need to be able to 'talk' to the computer to turn off sensors and stuff? Obviously if I stay carburetted it affects my choices a bit.

Steve Aichele


Provided you get the EFI wiring with the engine/efi hardware you should be OK. From memory you need to conect maybe 6 wires (ignition, fuel pump etc). There are exact details in past mails. What is a little harder is to understand how FI works in particular the need for a fuel return back to the tank. Having had a carb and eveolved to EFI I can say it is a very worthwile venture.

R Weston

If you can read (and digest) the huge amount of information (on how it works) available on the Megasquirt Website, ,

then you will be better placed to understand the few interconnections that are required.

If you use a Buick/Olds 215 or a Rover engine, then use Rover F.I, the hook up is very simple. You hook up a main power supply, fuel pump relay, and that is about it. Up through 1994(?) the engine harness is pretty much stand alone. The later systems do not use a distibuter, requiring a crank trigger, & more integration of the engine wiring. I also ran a wire from the electric fan to a sensor wire in the FI harness resulting in a higher idle when the fan was running. I may have forgotten a connection, someone else on the list will surely chip in.
Jim Stuart

With the 3.9 Rover EFI it's easy.
Your need a 12V power supply wire for the computer (obviously).
You need a wire off the ignition back to the computer.
I put fuses on these.
That's pretty much it; the rest of the computer/efi/engine is independent of the rest of the car.
You CAN run the fuel pump(s) off the good old MG wiring and ignore the EFI set up if you like. In fact there is an advantage to this because the Range rover speed limiter apparently works by the computer detecting the high speed (120MPH apparently) and switching off the fuel pump. Never the less I learned this AFTER I had gone to the trouble of wiring the fuel pump(s) off the computer controlled relay. So you may also choose to have a power supply to the EFI fuel pump relay thence to the pump(s).
Actually the fuel supply is much more involved and as it eventually turns out also not so hard.

Fuel supply, you need to pump petrol at high pressure to the fuel injectors on the engine, and return the surplus to the tank. The obvious approach commonly adopted by the auto industry involves welding a swirl pot/antisurge tank into the bottom of a new fuel tank and then putting the pump in that tank at the bottom to protect against fuel starvation . You will need an access hatch (if the pump fails) and electrical wireing set up of some kind. This will be expensive and /or time consuming and moderately difficult.
Fortunately for you there is another way and I believe is actually the best solution because it is by far and away the easiest, cheapest and quickest to do. It also protects the fuel pump(s) a lot better and makes it much much easier should you ever need to change a pump.
Unfortunately for me I did try a large variety of more expensive and very difficult approaches, before settling on the following.
Buy the very late model (and readily available) fuel gauge sender. This incorporates a fuel pick up of its own. Use this as the fuel pick up and the old pick up as the fuel return.
You obviously need to buy a high pressure fuel injection pump (Bosh pt no. 0580464070 and cost $140 Australian). These pumps must be used with a filter ($20 Kmart) otherwise they are history in no time. None of these high pressure pumps draw/suck very well at all and will cavitate and be very noisy unless located level with the bottom of the fuel tank. They draw even less well with a filter on the line. Regrettably there is no room next to the MG fuel tank in MGB's for anything like fuel pumps and their very large filters. Handbrake cable, axle, springs and exhaust all get in the way.
The solution is to use an "Auto-suction vane cell pump" This is a small low pressure, high suction, high volume rollervane pump which is readily able to keep up with the larger high pressure Bosh pump. This feeder pump will draw petrol through a larger filter up to one meter above the fuel tank. Made by Pierburg in germany and this Auto-suction vane cell pump's part no. is 12001. it can deliver 0.5 bar when used as a primary pump. It cost $95 Australian (apply exchange rate to get an idea what it might cost localy)
If you use the a large half litre size fuel filter this will (as well as filtering the fuel) act as an external anti surge buffer (swirl pot) and protect against surge starvation.
So late model pick up with a fuel line running to a big cheap fuel filter thence to small high volume feeder pump thence to main high pressure pump thence to engine then back again. You can put the pumps etc in the boot if you like. It might take you a couple of hours to set up.


I'm still in the early stages here, with candidates in the running including a tuned miata motor, a 60* GM V6, or the ford 302. The 215 would be great, but they aren't on every street corner the way these others are, and I'm not looking for a show car, just a little entertainment and some more zip. Cost is very much a factor, but the shell needs a fair amount of body work already so I'm not as concerned about that aspect.

Thanks for the input, I'll probably be doing bodywork the next 6-9 months (sills, floors, and a few other patches) anyway, just wanted to have an idea of what to watch for in the junk yard/classifieds.

Steve Aichele

If you got Ford, the wiring can be tedious, but you really just need a 12 constant for memory, a ground and a 12v ignition hot. While you may want to run these true relays etc for lessen loads those are really the ones you need. I would recommend (if you want to stay under stock hood with minimal chassis mods) finding a 94-95 Mustang GT donor car, or maybe a 91-93 Tbird (Not sure on Tbird intakes and distrib) The 94-95 stangs are the lowest profile set-up you can get from the factory or aftermarket.

If you go mustang there are also tuners out there (twEECer) that will let you program almost any part of the stock ECU, including rev limiters, timing advance curves, fuel curves, etc, etc. PLus there is TONS of info about the in depth workings and wiring of the Ford EFI due to the strong tuner market here in the US.
Larry Embrey

This thread was discussed between 15/08/2005 and 16/08/2005

MG MGB GT V8 Factory Originals Technical index

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