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MK3 TANK SWAP

 

This swap is actually easier then it looks.

 

On the difficulty scale this is a cave man job.

 

First things first this is what you will need from a mk3.

 

NOTE: DOES NOT MATTER IF ITS GOLF OR JETTA. ONLY MATTERS WHAT FUEL. IF YOURS IS A DIESEL FIND A DIESEL MK3. IF YOURS IS A GAS FIND A GAS MK3.

 

Tank, straps(all three along with the nuts and any other attachent hardware for them), fuel lines(from tank to fuel rail), about 8-12 inches of the fuel pump pig tail, any fuel line clips you dont break when you pull the lines out.

 

heres a pic of the mk3 tank out of the car with the lines. this is how i pulled it out of my old mk3. it would be easier to pull the lines off of the tank and drop the tank and then fish the lines out but i never do things the easy way. not pictured are the straps, hardware clips and pigtail.

 

This diy can be used for removing the mk3 tank. I will make notes on whats different between the two as we go.

 

if you can your best bet is to drain the tank BEFORE you remove it.

 

disconnect the lines at the fuel rail(mk3) or fuel distribution block(mk2). Undo hose clamps and pull plastic fuel lines out of their connections. on mk3 Blue is return and black is feed and the white is the vent and mk2 im pretty sure is the same but ill have to go look at my old tank. you do not need to remove the vent line from the car on the mk2, just unplug it from the tank. on the mk3 i would just take all three just incase you need the extra line. when you remove the lines the rubber lines should be held above the fuel distributor so they dont leak everywhere. fuel leak= fire hazard.

 

after the lines are disconnected go underneath and start popping the feed and return lines out of the clips and pull the lines out of the rail. youll see what i mean when you get under the car. You will want to jack up and support the rear axle. give yourself enough room to get under the car and move around.

 

as soon as you pull the lines stick them under the gas door so they dont leak like so.

 

nows when you need to decide if your going to reuse the fuel in the mk2 tank. if you are like i did you can do one of two things. if the mk2 tank is under a half tank you can stick both lines from the mk2 tank into the filler neck of the mk3 tank(it should be already emptied before you are trying to install it anyways) or if you have more than a little under a half tank transfer it all into a sutible container like this. you may have to have multiple cans but remember BOTH mk2 and mk3 tanks are roughly 15 gallons so you should have enough containers for what ever you have in the tank. if you decide to transfer it from mk2 to mk3 remember fuel isnt light. figure about 8 pounds per gallon roughly so half tank would be around 50-60 extra pounds.

 

i was lucky enough my parents had a 55 gallon fuel drum that i used to hold the good fuel from the mk2 tank. plus the drum was half full so i kinda topped off the tank when i put it back in.

 

the way i drianed the fuel out of the mk3 tank was a little questionable, i drained it into the fire pit out back. only because by the time i got to draining it the car was already gone, plus the fuel was atleast six years old so it didnt light so easy later. all i did was found a 1/2" rubber hose that was about two feet long and stuck it down the filler neck and tipped it up to where the filler neck was pointing down into the fire, supprted it so it didnt fall over and left it sit for an hour or so. i did run into one issue... getting the rubber hose out. i had to pull on it slightly and twisting it as i pulled. if you can find some better way to drain it please let me know.

nows the part where you may need a helper. if your using multiple containers you will need you or your helper to swap the cans when they get full and your helper or you to pull the jumper when your swapping cans(if your pumps are good fuel shoots about 4-6 feet out of the feed line... dont ask) and when the tanks empty. if you have a tank big enough or drain it straight into the mk3 tank you 'can' do it alone like i did.

 

anyways heres what you need for a jumper. two spade terminals and a length of wire. can be short or long. all that matters is it goes between the two terminals you see mine plugged into. i did mine long so it was easier to pop out if i had to quickly. when the tanks drained pull the jumper, put the fuel pump relay back in and disconnect the battery.when i plugged my jumper in the fuel pump ran with the key off. so be ready for that.

 

after this i got into getting it done and forgot about detailed pics. ill have to go out and get some pics to add. so for now ill just describe what to do and post the pics i have.

 

the mk3 only has one pump. unplug the wire connction and cut about 12" of the wire.

the mk2 has two pumps so you will need to disconnect the intank pump plug and the plug on the under car pump.

 

on the mk3 there are two nuts holding the fuel filter in. remove those and do not loose them.

on the mk2 there are four nuts holding the external pump and fuel filter box on. remove those and disconnect the wire plug on the pump.

 

the only lines you need to disconnect are the ones you already disconnnected in the engine compartment and the ones on the tank.

 

now back up top disconnect the fuel lines. until you drop the tank in a bit you probably wont be able to get to the vent.or pull the lines out since there is a fuel line clip between the tank and trunk floor. atleast there was on both my old mk3 and my mk2.

 

now take off the passenger(right) rear tire off and remove the bolts on either side of the filler neck(mk2 has two, mk3 has one)

left is mk2. right is mk3. notice the differences in the necks and the rubber thing

 

Now to drop the tank.

 

before you drop the tank you will need to push the rubber around the filler cap off the metal of the body of the car.

 

on mk3 you will be alot happier later if you mark the straps location and direction. youll be using them since the mk2 straps arnt long enough.

after that get a floor jack and put the pad at the center of the bottom of the tank. dont worry if its overlapping a strap. give it a little pressure up.im talking a half a pump after it touches the tank. then follow the straps to their ends and remove the bolts. note where the two held by the bracket are.

 

after the five bolts are out slowly start lowering the jack and jiggling the tank until you can get to the vent line unless ypu already disconnected it.

 

on mk2 leave the vent line in the car

on mk3 remove it with the other two lines. you may have to chase it forward and disconnect it where it ends.

 

.now lower the tank slowly(meanwhile making sure you didnt miss anything) until its alll of the way down.

 

the only way i found to get the tank out or the new one in, once its on the ground,was to spin the tank to the gas cap points towards the front of the car and slide it out so the filler neck goes between the back of the fender and the rear brakes.

 

once you have the tank out you may want to swap the rubber piece under the fuel cap(the one you had to pop off the body metal earlier) from the mk2 to the mk3 tank. to remove them remove the fuel cap then pull them off. set them next to each other and compare them and decide which one you want to put on the new tank.

 

now crawl back under the car and remove the mk2 fuel lines and take this chance to clean any dirt off the body before putting the new tank back in.

 

after its clean replace any broken fuel line clips with the ones you should have from the mk3 (they unscrew like a nut) attach the fuel filter housing to the two bolts that it lines up on where the under car pump was and clip the line into the clips towards the tank. next clip the return hose into the same clips from the filter to the tank. dont clip them in from the filter forward yet.

 

now both feed and return lines should be just under the fuel pump acess hole in the trunk/hatch.

 

now get the tank in place under the car the same way the mk2 tank came out. the vent line should be temporarily set between the in and out tubes on the pump. after that put the jack on it and raise it up very slowly.

 

attach the drivers side strap loosly and the filler neck bolt and the rubber around the filler neck. then the other two straps and tighten them all down. dont forget the filler neck bolt.

 

back in the trunk/hatch connect the feed and return lines and stick the vent from the car into the vent from the tank as far as you can. dont worry if its loose. when i figure out what i need for mine ill fix it and update this.

 

plug the connector you cut off the mk3 onto the fuel pump and decide and cut the mk2 wires. on mine the colors matched but two wires were swapped on the mk2 plug. if your car is ce2 it will be as easy as matching colors and crimping them together. ce1 youll need to figure out which wire is what because as far as i know the colors are different then ce2.

 

 

last and final two step before testing everything.

 

put a cap on the black hose(you dont want crap in the line) and slide it into the same hole you pulled the mk2 lines out of and clip it into the clips. back under the hood connect the black line to the hose going to the fuel distributor. here and on the return you will have two male pipes so you will need two 2-3" piece of 3/8" rubber hose  and four(two for each) hose clamps to connect the two.

 

repeat the above for the blue line and connect it to the fuel pressure regulator hose.

 

after those are hooked up if you didnt put fuel in the tank now is the time to do it.

 

after youve done that check everything reconnect the battery and turn the ignition on and off a few times before you start the car to make sure the pump works. if it doesnt work like mine it might just be siezed. i didnt take any pics but i tore mine apart and got it unsiezed. its worked fine since.

 

Now start the car and enjoy not having to deal with two pumps. Your welcome.

 

 

 

This pic is for reference. the top line in the pic is the return line and the bottom is feed. if your car wont start make sure you dont have these backwards like i did.

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