Hi, So I am working on trying to fix a leak coming from the gas tank area, I am currently just replacing all of the lines. Well after I dropped the tank I noticed that one of the steel lines feeding back (I think return line). Was left open. It also looks like the PO installed a after market filter as well? Or atleast I didn't see it in the FSM. Should I get rid of the filter, run line from open end to top of fuel pump and then move the line going in to that aftermarket filter to the top of the fuel pump?

I circled the open steel line in orange, and what I think is the after market filter in Green/Yellow.

Also What's up with this red wire feeding into fuel pump?




Thanks for the help.

 

Wow, this looks like a car fire waiting to happen. I'm glad you dropped the tank and are trying to sort it out. Several questions:

Can you see if the stock fuel filter is there? It bolts to the driver side frame rail at the back of the engine bay near the firewall. If it's still there, I would replace it with a new OEM unit (they're like $30) and remove the aftermarket unit entirely.

The hardline connected to the filter in the photos (left, if looking from the rear of car forward) should then be connected to the supply from the gas tank, which I believe is on the left in the 1st picture. The return line, which is the unconnected one, should be connected to the other fitting on the fuel tank cover.

How big was the leak? If the return line wasn't connected there's a good chance all of the returned fuel was just spraying out the hardline and onto your rear end...

It looks like there are 2 "in" lines on that fuel filter... do you know what they're each for, or is that just a weird angle and the 2nd hose isn't connected?

 

What a butcher job! I would delete all that crap and go back to stock system. As Kellis said, the original fuel filter is attached to the lower left front frame rail. It's held to the frame rail with a bracket. I'm not sure what's left of yours, but Atkins Rotary still sells the bracket (https://www.atkinsrotary.com/store/8...6-13-484-.html).

There are four hard lines that run from front to rear along the driver's side frame rail. I circled them in photo below.



These are the four lines circled in blue. From left to right, they are 5mm rear brake line, 8mm fuel supply line (high pressure), 8mm fuel return line (low pressure) and 5mm fuel vapor return line. I believe that the 5mm brake line is still available from Mazda. The three remaining fuel lines are NLA from Mazda. There may be shops in your area that will custom fab these fuel lines if you give them the original lines to copy. From your photos, I'm not sure how the other guy used those lines, but obviously the open lines must be the return line. It also looks like he has two rubber hoses going into the hatch area. I'm not sure where those would go to unless he ran the hoses inside and back to the engine. In any event, it does not look very safe.

 

Thanks for all the great info! I have the oem filter already hooked in. I picked up a new one when I was swapping everything over to this new body. So when I followed it back and found this second filter and an open line, I knew it didn't match factory. Just wasn't positive on what I was looking at. going to correct the lines and give it test tomorrow. Also those two lines going into the trunk area were plugged into the fuel pump originally.

 

Interesting. Are there any markings on the fuel filter? If it is connected like that, maybe it was actually an aftermarket fuel pressure regulator and not a filter. In this case it would make sense that the stock return line was unused and there was a second line going back to the fuel tank. Either way, I would recommend returning to stock form as discussed above.

While you're messing with the fuel system, check to see if there is still the fuel pulsation dampener (FPD) on your primary fuel rail. These are known to leak gas onto the engine and cause fires. Fortunately you can just use a banjo bolt to remove it, like this one:

FPD Banjo Delete

 

Sorry I forgot to get back to you. This was the filter. Wix 33737 Fuel Filter.
Anyways, I got all the lines fixed, the car kicked on and there were no leaks. But now I have run into a new problem. I noticed that the s4 T2 and s4 NA have different fuel pumps? Since this was a donor body I assume the old tank has a NA fuel pump. The car drove decently down the road, but I only put about 1 mile on it. I tried to get the fuel pump from my T2, but every screw was rusted on the fuel hat. I didn't want to deal with that headache so I decided to just order a Walbro 255. For now, is there any danger in driving the car around my neighborhood for troubleshooting while I wait on the new pump?

I will check the FPD tomorrow, a $20 delete for engine fires seems like a smart move.

 

I don't think there's an issue using the NA pump as long as you're not beating on it (i.e. getting into boost a lot).

Did you ever look into the wiring? It looks like they tried to bypass the stock connector on the fuel pump cover, but it turned into a hack job.

 

Sometimes those old rusted screws can be a bitch to remove. You might want to try a lots a penetrating oil and an impact driver. FYI, Atkins sell SS replacement screws (https://www.atkinsrotary.com/store/I...83-30-408.html).

 

That's a GM filter/regulator for a closed loop fuel system. I know because I used the same one on my LS swap. Was this car LS swapped by chance?

 

Yeah that is what I noticed from the reviews for the filter, I don't know what they were trying to do to the car. But I think they had planned that? When I picked the body up it had no motor, a T2 diff, front harness was cut into, wix filter, and a Mallory Fuel Pump was in the a bag in the car. I just ended up tearing all of that out (except T2 Diff).

 

Yeah I checked out the wiring, seems they just hardwired into the fuel pump they installed. Going to check what fuel pump it is later today.

About the FPD banjo bolt replacement. Does this look like it was already done?

 

I'm not sure if you might have already found out about your FPD question.... But if not, if I'm not mistaken it is on the other end of that same (shorter) rail.
For example, I found this on the web(this is an FD) but the FPD is the plastic thingy, and your photo seems to be focused on the other end with the metal U tube. The FPD, It should be facing the firewall if that makes sense.