84-85 Fuel tanks The facts.
 

I've noticed a few questions and misconceptions about the 84-85 S3 fuel tanks lately.

This thread will address the myths and facts between the FI and Carb, (13b/12a) tanks for the S3 only.

MYTHS:

1. The SE has baffles, the others don't.

2. You can't interchange the tanks.
a. Can't use an SE tank with a 12a.
b. Can't use a 12a tank with a 13b.

Facts:

1. Both tanks have baffles. The 13b/SE tank has a 'cup' that the fuel supply and return tubes sit in.

2. Yes you can.
a. No problems or risks with this swap. It is a direct fit.
b. You can, but since the 12a has no 'cup' to maintain a constant fuel supply for the pickup, a surge tank is recommended. This becomes especially critical if you are boosting!

Both tanks are identical in construction and configuration, with the exception of the 'cup' in the SE tank.

Both tanks have the same bolt pattern for the pickup and return assembly, they ARE interchangeable.

Note the pics below. I have yet to figure out how to include them in the body of a thread, so bear with me. (But Jon has... so here I come to edit!)

Pic 1. 12a tank on the left, 13b on the right.
https://www.rx7club.com/attachment.p...hmentid=107639
Pic 2. 12a pickup assembly on the left, 13b on the right. Note difference in the filters and the size of the hard lines.
https://www.rx7club.com/attachment.p...hmentid=107640
Pic 3. The 'cup' in a 13b tank. Not a good pic, but you get the idea.
https://www.rx7club.com/attachment.p...hmentid=107641


For those of you who are doing 13b swaps, in a non-SE, I recommend the SE tank, and the SE hard fuel lines. If you cannot find a good SE tank and lines, then add a supply line the next size larger, use the existing supply as a return line, remove the original return and add a surge tank. The easiest way to do this is source an SE pickup, otherwise you will need to have a larger pickup tube added into the assembly.

I hope this clears a few things up.

Scott.

The cup is very similar to the one in the FC tanks.Many people call that cup a slosh baffle (thats what it does) so that may contribute to the,"12A tanks have no baffles" myth.Just a misunderstanding caused by different terminology.Both tanks have bulkhead baffles going from top to bottom,but only the SE has the pickup baffle around the intake/return pipes.Good pics!

You might want to note that when swapping an FB (SE or non) tank into an SA car, you need to cut the spare tire well and raise it up about 2" for the tank to sit flush.

The SA spare tire well is deeper then FB (SE for sure)

That was the main reason for this thread, thanks clarifying my 'cup'

That is why I limited this post to be S3 specific. I have no experience with tank swaps into the earlier Series, therefore I posted no information about them.

I would rather post no information, than information that is questionable or in doubt.

I've owned 1 S2, and it met the sawzall quickly, it was really that badly rusted. Most of my experience is with S3's and S4's. The S4 tank is a definite no for a swap. The S2's, I do not know if they are interchangeable or not.

car won't start
 

I took out the old gas tank last week and put in a different one (both for SE's) and now the car won't start. It will crank but it won't turn over. The fuel pump will only turn on when the door in the air filter box is pushed open. I checked the fuses and I know I put the right hoses on the right metal fittings on the fuel tank. So, any suggestions?? And yes I put a couple of gallons of gas in it.

Thats a good bump.

S2 gas tanks are the sae as S3 12a 84/85 tanks but the fuel sender has only two wires

thanks, Trochoid. :)

+1

I wish someone had a pic of a S2 tank and a S3 Tank next to each other like that

The S2 tanks also have the fittings welded to the tank (making it a real pain in the ass to seal the inside of the tank without clogging them), whereas the S3 tanks have them on a seperate plate that is attached to the tank as shown in the original post.

Hmmm you are correct I forgot that, I am running a 83 tank in my 84 with no issues though, of course it was a sealed tank with a clean inside....

Yea they will fit right in, any 81-85 tank will interchange with each other. Mine luckily was pretty clean so I didn't use the tank sealer I got, but if one needed to it would be a pain in the ass to keep the lines from clogging. Oh well...

gsl-se fuel tank is mazda part #

FA66-42-110A its still available

fuel pipes are not, FA66-42-180

intank fuel filter (didnt know they had one! time to change it!)

is G037-42-113A for 13b and GA97-42-113 for the 12a

Thanks for the part numbers j9fd3s. Hopefully the tank in my PA is still in good shape so I won't have to change it out.

But seeing as it is boosted, it almost seems like using the SE tank might be a good idea. What are everyone's thoughts on that?

Junk that idea. Come over and pick any parts you want from DoLucks SE. Door panels are spoken for. Im keeping the suspension, short block and tranny.

Everything else are up for grabs in exchange for a 12-pack of heines so there is no entrance fee.

I have a feeling that when you take out that gas tank, that you will probably find it modified, and may if even had a baffle installed and stuff.

DJ, that very well may be true. It wouldn't surprise me, most everything else I've found so far has been modified.

Wacky, hold on to the gas tank for me for just a bit. I might take you up on that trade. :)

Zach

SA and FB tanks do not interchange due to the size difference of the spare tire wells in the SA/FB bodies. SA's had a full sized spare and a smaller volume tank.

Where can I find the 13 b tank????
Please help :)

know this is a old thread but I am in search of the pickup assembly 12a for our ‘85 RX7. Can not find just that part. Any suggestions? Thanks

Try placing a WTB (Want To Buy) in the For Sale section instead of posting in multiple threads and junking them up. This is the Technical Section. for issue/solutions. Thanks for understanding.

New ones can be bought here. I would not trust the lifespan of a used one.

https://www.atkinsrotary.com/store/8...54-60-960.html