Wrote this FAQ for GroovyCarrot who was asking about a GT conversion for a post-84 (larger tank. bigger brakes) mk2 on uk-polos originally but I think its worthy of here. Basically lists all the bits that need swapping/adding for converting a mk2 to injection. Its possible to do all this using the original engine, but most people prefer to use the mk3 GT or G40 engines for conversions. Fitting and removing of an engine isnt covered in this FAQ (because its the easy bit by most accounts :))

Most of this is valid for a mk1 and early mk2 as well, but extra provisions are required for fitting fuel lines and there are complications involving the fuel tank (either change the tank and rear axle/brakes to later stuff or make the original tank deeper with a hammer and a block of wood )

NB - fluxco modified the mk3 tank pump pickup to fit a mk1/early mk2 tank by removing the non-return valve above the strainer. I think the only downside is the pump may take more on/offs of the ignition to fully prime the system.

So anyway, here goes:

Fuel Tank - Ideally you want a mk3 one as the internals differ to a mk2 slightly. Its ok to use a mk2 one though, you can join the outlet and inlet together on the bottom of the mk2 tank.

Fuel lines - You need everything from a mk3 for this one, Including the brackets that run under the car and around the rear axle to the fuel pump/accumilator/filter housing. You dont have to use a GT car for a donor as far as the fuel lines go, but ideally youd have the GT inline pump for the higher pressure it puts out. On early mk2s (pre 86) there are no bolts on the underside of the car to support the fuel pump bracket or extra fuel line brackets. I've been informed the best way of adding these is simply with self tapping screws.

Exhaust - I used a full mk3 system on mine (decatted) to incorporate the lambda probe. Alternatively you can use a mk2 system, you just need to add a threaded hole for a lambda proba on the downpipe. If you do use a mk3 system its best to do the lot; from manifold right up to backbox. (you may have to shorten the tailpipe)

Additional wiring - Again ideally you want a donor car to take the fuel pump wiring from. I saved everything from my scrapped GT so I had all the bits I needed fortunately. The wiring is really simple so theres not a great deal of hassle involved in removing it. Basically theres 3 extra wires on top of what the mk2 has; Two of which are a +ve for the fuel pumps and the third is an earth for the inline pump (the tank pump can use the earth of the fuel gauge sender) The +ve wire(s) are red with a yellow stripe and they both can be connected to the loom via the additional fuse that mk3s have (Yellow one that is part of the fuel injection loom - which clips above the fusebox)

Engine Bay Wiring - You need EVERYTHING from the GT that plugs into the fusebox, just the ECU loom wont do.

Engine bay wiring differences. On mid mk2s alot of the plugs are different to mk3s, they still use spade connectors instead of the more modern plug design. The plugs that are different are:

- Blue and Black temp sender

- Horn

- front indicators (side repeators are fine)

- Sidelights

- Reverse switch

- Starter motor solenoid wire

- Oil pressure switch wires.

All of these parts can be sourced from late mk2s (whenever they switched over to having plastic timing belt covers is when they started using the more modern connectors. G reg onwards or there abouts I think.)

Additional

Theres a couple of other small differences worth mentioning:

- Expansion tank level sensor might be needed if your car doesnt have one. (late mk2 expansion tank) This wasnt a problem on mine either because it had one and the plug was the same, or it didnt have one and I had a late mk3 loom which didnt have the plug anyway.

- You may need a different radiator fan depenging on what youre converting to. (some are two speed and some are single speed and the plug on the loom is different. You probably also need the temperature switch on the radiator. You can retain the original radiator setup though for the most part. (I think theres a slight difference in the return for the expansion tank so you might want to use the mk2 thermostat housing instead.

- Windscreen washers; If like my ranger your car has 2 tanks, the wiring on the GT loom needs altering slightly. The deal here is on later ones the pump goes in two directions, forwards to do the windscreen and backwards to do the tailgate, This is done by having a switched live and earth. Now for some reason if you leave the GT wiring alone the front washers wont work if you have the separate tank setup. But if you replace one of the wires (I forget which) with an earth it works fine, and doesnt effect the rear wiper operation.

- The alternator bracket and alternator are sllightly different but it only matters if youre swapping alternators between the two engines (just swap the bracket with it)

- Last thing: For the rev counter to work you need to add a wire from one of the terminals of the coil to the back of the clocks. I cant remember right now which pin it is but its around pin 5 or 6 IIRC (red wire) As for which coil terminal it is just use trial and error.

Think thats it! Good Luck!

Its not the best written FAQ at the mo but all the basic little bits of info are covered. I'll tidy it up a bit when I've got some more time.

Awesome faq gaz, fair play to you mate

nice one... but this is why i love carbs!

Ah I thought this post was lost in the midsts of time!

Ah I thought this post was lost in the midsts of time!

Not when there's someone bored and signed off work browsing the forum dude

fantastic this should help no end

Just a quick add on, if you previously had a 4 speed box you may well have to change your antiroll bar to one from a 5 speed car as the gearbox will catch otherwise.

- Last thing: For the rev counter to work you need to add a wire from one of the terminals of the coil to the back of the clocks. I cant remember right now which pin it is but its around pin 5 or 6 IIRC (red wire) As for which coil terminal it is just use trial and error.

not saying your wrong because that was what i thought i had to do but kept the gt clocks and rev counter works fine.

Will this work on a mk2 1.3 golf? Thinking of dropping the 40's :(

better off asking someone like yeha about that.

Hmm. With the fuel tank what needs to be done, lift pump in the top? I have a plastic fuel tank, are the mk2 polos ones?

No the polo tanks are metal. You'll need some later gti stuff for the fuel pumps that deliver the right pressure. There's not much wiring to sort. You'll need to add a hole in the exhaust for the lambda.

What pressure does the GT pump run at - are you saying i could get golf GTi pumps etc, and connect it upto the GT system?

- Windscreen washers; If like my ranger your car has 2 tanks, the wiring on the GT loom needs altering slightly. The deal here is on later ones the pump goes in two directions, forwards to do the windscreen and backwards to do the tailgate, This is done by having a switched live and earth. Now for some reason if you leave the GT wiring alone the front washers wont work if you have the separate tank setup. But if you replace one of the wires (I forget which) with an earth it works fine, and doesnt effect the rear wiper operation.

I'm coming to the end of my conversion and popped a few fuses and can't seem to figure out switch wire it is?

hopefully get this sorted before it's MOT and custom Exhaust

sweet gaz, short but sweet :-D

i would just buy a mk3 lol

Verry handy these how too's cheers

just to clarify do i need a lift pump from a mk3 aswell as all the external pump/brackets? and the lift pump will just fit straight into my late mk2 tank?

just to clarify do i need a lift pump from a mk3 aswell as all the external pump/brackets? and the lift pump will just fit straight into my late mk2 tank?

as long as you have a late mk2 tank (which I think you should have) then yes you need the mk2f lift pump. Just loop the inlet and return together. :) Make sure you have g40 pumps but I think the GT is the same. The lift pumps are all the same on mk2f's i believe.

just to clarify do i need a lift pump from a mk3 aswell as all the external pump/brackets? and the lift pump will just fit straight into my late mk2 tank?

as long as you have a late mk2 tank (which I think you should have) then yes you need the mk2f lift pump. Just loop the inlet and return together. :) Make sure you have g40 pumps but I think the GT is the same. The lift pumps are all the same on mk2f's i believe.

ok that makes perfect sense! i have a higher flow rate external pump already so will just need the brackets etc and the lift pump

How much would you expect to pay for particulars like injector rails, digifant ECU?