30/12/2009

How to remove and replace a Porsche 944 fuel tank (Square Dash Model)



THE WHY?

If you've ever asked yourself "Should I buy an early (square dash) or a late (oval dash) 944?" then this article may be the deal breaker. Having put my 944 in for a service my mechanic discovered a leak that appeared to be coming from the fuel tank. No big deal I thought, I'll buy a second hand one from a breakers or ebay. However upon further investigation it turns out Porsche significantly changed the material of which the fuel tank is made from between the early (square dash) and later (oval dash) 944. The square dash 944 (and 924) has a fuel tank made from steel, whereas the oval dash model has one made from plastic. More investigation reveals that the fuel tanks are also of different capacity (oval dash has the larger 80 litre capacity, compared to square dash's smaller 66 litre). Even more investigation finally concludes that the plastic fuel tank will not fit the early (square dash) 944's as the cross-member that supports the transmission is non-removable and therefore blocks the insertion of the larger plastic fuel tank.

So the options I had were:

a.) Buy a new steel fuel tank from Porsche for near £1500.00!
b.) Repair the old tank
c.) Buy a good 24 year old fuel tank from a breakers £40.00

I went for option 'C'.

For the record and from research on forums it seems the steel fuel tanks are susceptible to cracking due to the vacuum that causes the fuel tank to contract and expand. They are also susceptible to corrosion, externally and internally.


THE TASK


You'll need the following tools and a lot of patience and a spare pair of hands:

Socket set
Spanners
Couple of screwdrivers (flat and cross-head)
Container to empty petrol into
Clamp-able pliers
Trolley jack or two
Axle stands
Waxoyl (Spray version) - optional
3M Scotch Weld 80 Spray Adhesive - optional



THE HOW TO


(Amateur mechanic Job Time approx: 2-3 days)

You want to start by emptying the fuel tank as much as possible before you start. I did this by driving the car until the fuel light came on solidly on the dash.

The next thing to do is disconnect the battery, as fuel and sparks don't mix.

Now undo the fuel cap to release any vacuum or pressure in the fuel tank.

Next slide under the rear of the vehicle and locate the main hose between the lowest point of the fuel tank and the fuel pump. If you have a fuel clamp or a pair of clamp-able pliers then clamp the hose nearest the fuel pump and proceed to undo the jubilee clip that fastens the hose the fuel tank.

Below is a photo of the fuel pump with the main hose removed.



With the jubilee clip loosened get your empty container positioned below the tank to catch the remaining fuel. Wriggle the hose off the fuel tank and catch all the excess fuel until completely drained. You can now undo the much smaller hose that is also connected to the lowest part of the fuel tank.

Jack up the rear of the car as high as possible and set it on axle stands.

Now remove the rear section of the exhaust by undoing the 3 connecting bolts on the exhaust tube in the centre of the car and then unhook the rear box from its rubber hangers (shown below).




Next remove the four bolts that secure the exhaust heat shield (shown below) to the underside of the car.



Now remove the transmission (See this post for instructions)

Now it's time to get inside the car. Start by completely removing the carpet from the boot area.

Next pop out the rear quarter window on the fuel cap side and completely remove the interior panel of the same side (See this post for instructions)

Lay down the rear seat and un-clip and pull back the carpet from around the side of boot of same side to expose the fuel filler cover (Shown below)


Undo the surrounding screws, not forgetting the two small nuts at the base of the cover. Then as shown in the photo above position a screwdriver in behind the cover either side and pull towards you. The cover may resist at first because of the black goo it is secured with, but it will come away eventually to expose the filler hoses (shown below).


Undo the jubilee clips on all the hoses and pull off, with the exception of the largest hose which you can slide upwards to reveal the corner inlet of the fuel tank.

Now lift the large silver heat shield square located on the floor of the boot to expose the plastic cover for the fuel sender. Prise this up to in turn expose the sender wires. Make a note of what wire goes where and disconnect them all (shown below).


Get back underneath the car and locate the two large straps at either end of the fuel tank (shown below)



Undo the bolts and unhook the straps, the fuel tank is now only supported by the steel cross member it is wedged over.

Get your hands behind the rear most edge of the fuel tank and pull down. Keep wriggling the tank up and down checking that the fuel filler hoses aren't trapped. This part takes a lot of effort and patience as the tank is an extremely tight fit over the cross member and has probably never been removed before. Trust me the tank will eventually come free. You may need to unbolt the fuel pump from its rubber mounts if it gets in the way.

With the fuel tank removed we can now clearly see the fixed cross-member that stretches the width of the car underneath and the fuel filter bottom right (shown below).



As stated at the beginning of the post I decided to source a replacement tank from a breakers yard, it had a bit of dent in the side and some surface rust that I cleaned off. I then Waxoyled the whole tank to prevent further corrosion. I would also recommend you get them to pressure test the tank as I did. This helps prevent the problem of putting a tank back on that is the same or worse than the one that came off. It may also be worth checking the condition of the rubber hoses as they may have started to perish and go hard after 24 years of use and replacements would probably be a good idea.

Here are a few photos of the replacement non-leaking tank that I sourced from a breakers (note the expansion tank hanging off the bottom of the photograph and the fuel sender top left in the first photo).






Not shown in the photos is the large foam pad that sits around the fuel filler neck part of the tank. I carefully removed this before spraying the tank with Waxoyl. It was then finally put back on and stuck down with 3M Scotch Weld 80 spray adhesive before the tank was reinstalled.

Tank installation is the reverse of removal.

For more information on the steel fuel tank cracks and repair procedure if you can't source a replacement tank then follow this forum post. It also shows the differences in dimensions of the early and later 944 tanks side by side.

11 comments:

  1. thanks this web site was the most help

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  2. What's the capacity of the fuel tank?

    ReplyDelete
  3. The metal fuel tank is 66 Litres (including 9 Litre reserve) and the plastic fuel tank is 80 Litres (including 8 Litre reserve)

    ReplyDelete
  4. Hey I hAVE a 1986 944 and the fuel pump is in hte gas tank. where can i find instructions to remove teh fuel pump from the gas tank?

    ReplyDelete
  5. Afraid I don't know, maybe ask on the forums at Pelican Parts

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  6. I have read about removal of the window before, and I still do not fully understand the consequence of this. I clearly see your screwdriver in the photo, but is that all the removal is for? and isn't there an easier way to get a driver in there?

    one other question - do you know if any of the filler tube/sleeves/etc. can be replaced without removal of the tank?

    thanks again for a super tutorial.

    ReplyDelete
  7. The consequence of removing the rear quarter is that is allows you to remove the rear quarter panel which is necessary to get to the fuel hoses from the filler cap.

    You could probably use a plastic bicycle tyre lever instead of a screw driver but the method is the same, lift the seal up from the inside and push the window outwards, then the rest of the seal will ease itself out.

    The tube on top of the tank cannot be replaced without dropping the tank, but the filler tube from the fuel cap can be.

    Thanks

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  8. how smelly did it get - did you seal up the ends of lines with anything while working?

    ReplyDelete
    Replies
    1. Depends if you like the smell of petrol or not I guess. From memory I believe I just plugged the lines with a bolt or two - anything that would fit basically.

      Delete
  9. were you able to remove the metal cover without deforming it much?

    if not, did you simply bend the edges back into position?

    ReplyDelete
    Replies
    1. If you are talking about the metal cover over the filler hose or the one above the exhaust neither were deformed in the process of removal.

      Delete