Category Archives: How To

How to replace the gas tank on a 1968 C3

I recently had a bit of an issue with some pinholes in my gas tank seeping gas which at first glance didn’t look to bad. But as the tank had been repaired before and my repairs didn’t hold it was time for a new tank. Thought I’d write up the process just in case anyone needs it in the future. It’s up to you whether you jack up and support the rear of the car as the tank can be removed without it. But it will give you a lot more room to work in which you’ll be thankful for later.


Try to drive your car to as empty as possible before starting to drain the tank. You can remove it without draining it but damn it will be heavy as you lift it out. You can partially drain it by removing the hose from the sender unit in the base of the tank, but this will still leave 5 – 10L of gas in there.

Best way is to siphon the gas out from running a pipe in through the filler cap as that managed to get most of it out for me.

Once the gas is out you need to remove the fuel hoses where they attach to the tank. Remove the large hose at the sender unit, and on the 68 the return hose is on top of the tank so it’s easier to disconnect the return hose at the hard line on the right hand side rail. On mine the return hose was perished inbetween the two so I didn’t have to remove anything unfortunately.

If you have a later model chances are you’ll have a charcoal vapour canister on the left you’ll need to remove at this point too.

Next I removed the sender unit and fuel outlet from the base of the tank. Although not necessary, it’ll save you from accidentally knocking it around while removing the tank later. It apparently takes a special tool, but I just used a screwdriver and hammer to gently tap/rotate the 3 lugs around until the keeper ring popped out. At this point I found the pickup tube was missing the filter sock which explained some crud in the carb when I bought the car. Unit was nice and clean though.
I also removed the rubber splash shield around the filler neck and removed the filler from the tank as well to make for easier manoeuvring later.

If you have mufflers out the back then they will be completely in the way if you try to drop the tank. Easiest thing to do I found was to loosen off the clamps where the pipes are usually joined just in from of where they pass though the crossmember in the middle of the car. Once loosened you can undo the hangers and “gently” rotate the pipes down and towards the outside of the car giving enough clearance later to drop the tank. Remove the spare tyre carrier and especially it’s top shield at this point as well to give you room later.

Once this is done the tank straps need to be loosened off. The bolts for these are on the rear crossmember and need to come completely out so the straps are free. Of course on my tank I found only one of the straps was even bolted down! Looks like they didn’t attach one so it didn’t put pressure on their dodgy tank repair. Once the straps are loose it is handy to try to slide the tank back and to the side so that it is supported by the rear crossmember and side frame rail as it will make removing the support easier.

The support bar runs under the front of the tank to support it. This is held on by 2 bolts/nuts on each side (or only 1 each side on my car). To get this off you need to slide a spanner (1/2” I think) in though the handy gaps in the frame rail to hold the bolt head so you can turn the nut underneath. Loosen off both sides and the support will just be held by the back of the tank straps. Once the support is loose you can rotate it around so you can get the straps out of the slots on the back of it. Once the straps are loose slide them off the side of the tank and remove them as it will be easier when dropping the tank.

Now you can push the tank towards the back of the car to enable you to rotate the front of it down to drop the thing out.

Once I got the tank off I found it had 4 previous repairs along the ridge where it sat on the support bar. Research shows this is common as the spots get a lot of flexing pressure from the support. Also looking inside the tank there was a lot of rust residue along this line as well as the tank being is a dodgy state overall.

Reassembly is the exact reverse of the above process but a few tips will make it easier. At the end you’ll end up with a nice shiny tank in there.

1. New tanks are usually just bare steel. You can either paint it, or do as I did and just spray it with a few coats of clear to give it a bit better protection from the elements.

2. The front support bar and rear crossmember should have an anti/squeak pad across the top of them. I threw away the 40 year old stuff that was barely there and just got some rolls of sticky backed felt from the surface protection aisle at the hardware store. The adhesive makes it simple to stick it to the supports and prevent it moving when you are messing round putting the tank back in. I also used it on the underside of the top of the tank straps to protect the top of the tank slightly. Just make sure you don’t use too thick a felt as it will make the straps a pain to try to do up later (ask me how I know).

3. The bolt on my tank strap was 1 ¾” long. I replaced both sides with 2” bolts which made starting the tightening of the straps a lot easier.

4. While the tank is out take a look at the drains from the rear deck. Like mine they may be jammed up with 40 years of dirt. For a quick fix I just poked around with a screwdriver to clear them a bit and blasted from the top with compressed air to flush it all out.

5. While the tank it out it could pay to take a look at the rails and give them a bit of a cleanup and rust protection treatment while you are at it.

6. Before tightening down the tank straps check to make sure that the filler is lined up on top with the opening in the deck.

7. Don’t put the old gas back into the new tank. Chances are if the tank was rusty there will be rust particles in the gas that you don’t want in your new tank. This is not so much of a problem if you have lined the new tank with a sealer like the POR15 gas tank kit.


Replacing the fuel pump in a 68

Well one more thing on Frankenvette needed replacing so here’s another short writeup in case anyone else needs the info. The following should see you through replacing the mechanical fuel pump on an early C3.

My pump had developed a couple of issues. First oil was misting out of the little vent hole in the casing of the pump and being drafted by the airflow up and onto the hood. Second there was a tiny gap in the casing (circled in the pic below) that was also venting fluid as well.

Simplest option was just to replace the pump with a new one. Total cost for me was about $50 for a standard Carter style replacement (which came with a gasket) and a metre of 3/8″ (10mm) fuel hose. You may also need some 1/4″ hose if you intend to replace the return line as well if you have one.

First step is to find someone with a lift as that will make this job a whole lot easier. Toothy Grin If not, then just raise the car up on ramps or support it with stands under the jacking points on each side of the car. Now clamp off the fuel hose at the tank as it will stop the fuel being pulled by gravity when you remove the line on the pump. Also disconnect the battery so there are no sparks while you’ve got gas dripping about. If you don’t have a A/C compressor in the way then the next bit will be a lot easier. If you do, then it’s time for a bit of contortion.

On the front of the block in line with the fuel pump there should be two holes in the block with the top one filled by a bolt. If you remove this top bolt and thread in a longer one (I used a 3/8″ x 1 3/4″) you will be able to trap the rod that drives the pump so it won’t fall out when you remove the pump. Believe me this will make life a lot easier when re-assembling things.

Next remove the soft lines to the pump. Now you may have a 3/8″ feed line and a 1/4″ return line to remove, or you may have a modified setup with only a feed line. Either way remove the clamps on the hoses and pull things off. It’s a good idea to have a tub or something to catch the gas that will drain out or you may end up lying in it when under the car for the next part. Next remove the hard line from the pump to the carb at the pump.

That’s the easy part done. Now time to remove the pump. It’s held on by two bolts. The first is nice and easy to get to from the top/front by sliding a ring spanner past the lower radiator hose onto it. More fuel will drain from the pump as it starts to come loose. Now there’s the last bold left. This you can get to from underneath with a ring spanner, just. On my car there was about enough room for about 1/8th of a turn at a time so this last bolt took a long time. Once it comes out the pump will either drop off or need to be pried off because the gasket has stuck so you are half way there and probably should go have a beer to celebrate.

Next if there are signs of an oil leak from behind the mounting play you may need to take that off too via the two bolts that retain it. I didn’t have a gasket handy so left mine for now. Either way you will need to clean up the surface as there’ll be crap from the old gasket all over it I’m guessing.

Easily cleaned up from underneath with a scraper as there’s enough room to get one up under there. Just be careful not to cut your radiator hose as it’s going to be close.

Now is probably a good time to take the hard line to the carb out and check/clean your filter and line as well. I found a whole heap of crud in my in-carb filters (from my old bad tank).

Getting the new pump on is a lot easier now you know how it all came apart. Put the gasket on the pump and feed the two bolts through it. This will hold the gasket in place while you fit the pump. Get under the car and feed the pump lever into the hole so it’s under the rod. Now you’ll need to try and hold the pump with one hand while trying to start one of the bolts with your other hand. Once that’s started try the same with the other bolt which will most likely be a lot harder due to the tight space. Do them both up tight once you are able.

Next refit the hard line from the carb, and the feed/return lines. I replaced the feed line at this point as mine looked old and was starting to crack. Apparently the original fuel line in a 68 was moulded so it would curve nicely to from the line to the pump. If you replace things with standard hose make sure you have enough so you can route it without causing a kink and pinching the line which will restrict the fuel flow.

Once the lines are on and the clamps tightened remove the clamp on the line at the tank. Also remember to remove the bolt holding the pump rod and replace it with the original bolt. make sure this is done up tight otherwise it will seep oil.

Now it’s time to drop the car down and reconnect the battery. Crank the car over a few times without pumping the gas pedal to get the new pump going and prime things with fuel. Once you think it’s right then give it some gas and try to start it. All going well you now have a sweet running car. After a minute or so stop it and go and check the connections at the pump for signs of gas or oil leaks. Tighten everything if there is and repeat the process. Now go have a beer because it’s well deserved.