1973.5T fuel tank

[Sunroof]

1973.5T fuel tank

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I have been a part of many 73.5T fuel tank threads especially on the issues of refurbishment, pre-pump filtering, etc, etc. Now its seems that my tank has come about 180 degrees and had bit me in the ass, so listen up 73.5T owners.

About five years ago I removed my tank and had it boiled (light caustic solution) at a local radiator shop who highly recommended using an interior coating named, "REDKOTE". I did my research and read that it was a DOD/US Navy approved coating for onboard vessel tanks from fuel to potable water. It was cheaper then POR15, very effective and bullet proof! So the shop applied two coats internally.

As the years passed, it has turned out that a lot of the coating has come loose (can it be that that internal baffle made of plastic could not hold the redkote?). I do recall seeing photos of a cut in half 73.5T tank that did show the baffling that was identified as plastic or non-metallic. As a result I have been left stranded twice now on the road. Re-start lead to a very noisey cavitating fuel pump (new Pierberg) indicating a blockage in the system. Adding a filter before the pump was highly suggested, which I have yet to do, but I see that as a temporary solution. My options is a new tank, which would only adds value to the overall restoration process.

Shopping for a new tank has been very interesting as prices amongst dealers and vendors runs the gamut. Most are confused with this year model. Complicating things is the need for the smaller capacity tank to hold my full size spare tire. The 1973.5T fuel tank with its internal baffles, swirl pot cup, internal meshed filter, etc, does make it very unique only to this vehicle. Could it be that the tank was engineered exclusively for first the CIS model and nothing else will work? Maybe its the full spare requirement.

Thats the question I raise here. Do I have any alternative?

Thanks
Bob
73.5T in Sepia of course

[manbridge 74]

Not an expert in 73.5 CIS tanks but others have run a full size spare with a low profile tire in a 74 and later. Perhaps a 74 CIS tank could fit?

The shop here advised me not to internally coat and I'm glad I did after hearing this.

It's possible you could have the tank cut open, cleaned, and welded closed with Wurth coating reapplied to cover up repair.

[Sunroof]

Cutting open my tank and dealing with all that internal coating could require sand blasting or solvent washing, etc, etc. I do not think it would be worth it considering the cost of a new 73.5T replacement. I am not sure if the 1974 tank is correct for this model. Something I will need to check out.

thanks
Bob

[RichardNew]

I have a 73.5 and I had the exact same problem. After about 10 years the coating broke up and clogged the fuel system. I would never coat another tank.

Richard Newton
Car Tech Stuff

[Sunroof]

Does anyone have the exact part number of the original 62 liter fuel tank strictly for the 1973.5T? I keep getting a replacement number (I am getting 91120190400) but that is not for the CIS model. I also heard of a company named TMP that makes aftermarket (galvanized) Porsche fuel tanks. I am trying to get a good bead on a reasonable replacement.

Thanks

[ossiblue]

To answer directly the question posed in your OP, the 73.5 CIS tank is a one-year-only design because of the ability to carry the full size spare and, thus, has a smaller fuel capacity than later CIS tanks. All CIS tanks have the swirl pot and screen filter and some have different placements/sizes of fuel inlet and out ports. If you want to keep your full size spare, you will need to find a new tank that is 73.5 specific (for the reasons above), if it's available, or purchase a used one and roll the dice.

BTW, the 73.5 carrera was equipped with the larger/later tank for more fuel capacity and required a small spare so it was a factory option at the time.

[Sunroof]

LJ,

If the 74 tanks onward all have the same internal components that changes the replacement price by quite a bit (several hundred actually). I thought the internal baffling was strictly for this 73.5T model. So its all about the spare tire?! When weighed against a tire saver spare or full spare common sense dictates to me that the 74 - on replacement is the wiser. Unless of course I want to be anal about originality verus trouble free driiving. The concern over fuel line fitting or changes in fuel hose diameter might be a concern here to. Very useful information. Thank you.

Bob

[ossiblue]

Lots of 73.5 owners have gone the later tank route primarily due to the cost. As far as the fuel connections go, you can do a little searching to find which later tanks are closest to what you have, or likely, someone who knows will post to this thread. Now might also be a good time to consider moving the fuel pump to the front cross member if you haven't already done so. Not original (but neither will be your tank) but it is a better location and is the one Porsche used in later cars. If you decide to do both changes, the location of the outlet/inlets in later tanks will play a lesser role as they were designed for the cross member location of the fuel pump.

[manbridge 74]

I can post a pic of the 74 tank outlets if you need it

[Sunroof]

Please,post a photo of the rear fittings for the 74 tank.

Thanks

[manbridge 74]

This tank is unlike most I've found on old cars. Ie, someone drained it before storage so no major internal rust. Disregard the hack PO hoses and clamps. I'm going to put it on the parts section soon.

New ones from Pelican are better as they are galvanized but may or may not have the same fittings. You'll need to ask.

[Sunroof]

Thanks.
Same rear hose fittings as the 73.5T tank.


Original 1973.5T tank number - 90120101022
Superseded by part number - 91120190400

Porsche OEM (has to be shipped from Germany) - $1800.00 (dealer)
aftermarket replacement - $840.00 -880.00

At these prices it might be worth looking at the 1974 - on fuel tanks or take mine out and flush it out several times to get as much crude out as possible and hope for a few more years.

Bob

[manbridge 74]

I would suggest finding the guy who works on the military stuff near you. They have a lot of experience with stuff that has been in storage and what works best without damaging internal tank plastics, etc.

Our host sells this tank which might work for you if you ask about the fittings..... half the price of $880.00

Pelican Parts - Product Information: PEL-TMP-9710

[Sunroof]

The tank you mentioned at PP got some weird reviews! But the 74 on tanks are much cheaper. For that price I could buy a tire saver spare and still come out better then the 73.5T tank. Besides the 74 has a larger capacity.

Bob

I work on a military base and the motor pool guys would need an act of congress to touch this tank!

[manbridge 74]

Around here this sort of work is subcontracted out. Look up Manley Radiator in Colorado Springs if you would like an old timers opinion on your tank.

You could also sell old tank for a good price to a DIY guy wanting a 73.5 year tank. Not being perforated is key here.

[manbridge 74]

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[BoxsterGT]

Bob-
I am curious if your 73.5 CIS car has steel lines running thru the tunnel or the white nylon lines?
Trying to verify just when Porsche actually started using the nylon hardlines.
August 1973 was the beginning of the 74 Model year and they were using these white (now Brown) lines for only one year I am told.
Good luck w your search.
Len

[Sunroof]

Len,

I am sure which lines are in the tunnel in my car as I have never accessed the tunnel accept to re-install the hand throttle cable attachment piece or mess with the handbrake. My fuel lines are new going from the tank to the tunel and from the tunnel to the pump or return. I did not install these.

Regards,

Bob

[E Sully]

My 911T cis is July 1973 according to compliance sticker, is has original steel fuel lines in the tunnel.

[Sunroof]

Nice to know.......................