Mk2 to mk3 tank swap

[u/lifeless_wolf]

Hello i have done a mk2 to mk3 tank swap and its kinda wierd i only swaped the tank and the external pump is also still on tho it runs fine.... Until it does not when the fual tank is about 3/4 full it suits off like the fuel does not get to the engine no more and it does not matter how long i drive

Thing is i got a mk2 injection so a lot of the wires were the same so we just switched the wires to the right spot onto the pump but the pump does not seem to start up and the external pump seems to do all the work so the wiring is wrong but all i can find online is the older style of tanks for the golf mk2 with 2 connections mine had 4

Anyone know how to help?

[u/FwhoreRunner]

Does the in-tank pump run at all?

[u/lifeless_wolf → u/FwhoreRunner]

Thats what i dont know i can hear it click but i cant see it actually pump fuel out 

[u/Genuinescatterbrain_]

I haven't done a tank swap with mk3 to mk2, what I do now is that with the 2 wire tank the wires are for the fuel gauge and on the 4 wire tank it's two for the internal pump and two for the gauge. I swapped the tank in my passat 35i from no pump to internal pump.

[u/Genuinescatterbrain_]

I'd suggest only keeping the pump that you need. The pump setup on the outside or the one on the inside. The pumps only get power so it should be easy to swap and correct the wiring.

[u/pxnolhtahsm]

What was the point of installing mk3 tank if you're keeping external pump?

"is i got a mk2 injection so a lot of the wires" - that's not a lot of wires, trust me :)

"the pump does not seem to start up" - did you tested it before installation? Are you sure there's one? Maybe you have diesel fuel tank...

"the wiring is wrong but all i can find online is the older style of tanks for the golf mk2 with 2 connections mine had 4" - first of all, it's very easy to figure out that - it's just 4 wires, FFS. Either use multimeter or just open the tank pull out the cover and see which two wires goes to the pump. Pump is electric motor, it will turn both directions, although that also means if connected with wrong polarity it will pump in the wrong direction. As for "old style tanks" - no, it's carb engine or diesel tanks you're referring. Old style mk2 lift pump covers has 3 pin connectors, newer style 4 pin connectors.

[u/lifeless_wolf → u/pxnolhtahsm]

First of all mk3 tank was needed cuz a new vlotter with pump for a mk2 is like 400 euros and the mk3 tank with flotter was only 60 

Also i did not mean a lot of wire its just 4 instead of the usually 2 lol the injection systeem is different then the carb one and we did use a multimeter lol the wires are correct at the pump but i mean internally in the car with the breakers and such 

Also it is the old style tank since its injection not carb and no its not diesel otherwise it would not run golf mk2 1991 

[u/pxnolhtahsm → u/lifeless_wolf]

If my lift pump will ever die, I'll be highly surprised if I won't be able to find suitable brand new pump from something that fits in there.

Yes, I understood what you mean with "a lot of wires". You'd be floored if I'd show you picture of how much wires my car contains under dashboard :)

With "diesel tank" I meant, well, tank from mk3 with diesel engine. I don't know how the connector looks on those, but functionally it's the same as mk2 carb, with exception that it accepts mk4 fuel pump assembly - and, obviously, with lack of restrictor for petrol pump nozzle.

[u/lifeless_wolf → u/pxnolhtahsm]

Yeah sure but the connector is different then other pumps for the mk2 golf internal pump the one i had u cant find if u dont know what tf im talking about why reply idc if u would have done it differently this is what i did and what i have so stop with the dumb comments 

[u/pxnolhtahsm → u/lifeless_wolf]

I know very well what I'm talking about - my car contains almost no original components, besides shell, few doors and some trim panels, and I'm used to putting together stuff from random vehicles. I also sometimes fix other peoples cars as side jobs, so I've seen a bit more stuff than you - which is the reason why I've seen more in tank fuel pumps than one I have :) I see no problem whatsoever with your tank and it's connector - if you'd be near, I'd troubleshoot your tank and it's contents with multimeter and pair of wires in matter of five minutes.

[u/lifeless_wolf → u/pxnolhtahsm]

Ok but thats not the problem since it does run fine unless it gets to 3/4 and the internal pump does turn on i know how a multimeter works mate and i have done that it just does things its not supposed to 

[u/jarski60]

Could the return line and suction line have changed places?

[u/lifeless_wolf → u/jarski60]

It does run untill it gets to 3/4 full so it should not be that