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Engine SwapEverything about swapping an engine into your Third Gen.....be it V6, V8, LTX/LSX, crate engine, etc. Pictures, questions, answers, and work logs.
I'm swapping a 4th gen gas tank into my 1988 Camaro because I also swapped an LS1 in and this seems to be a logical upgrade to handle the fuel requirements.
My issue is what to do about the EVAP system. Does anyone have a specific solution to adapt the EVAP system present on the 4th gen tank to a 3rd gen car? I don't mind if I have to use the stock 4th gen sender since I'm using a Dakota Digital dash and the fuel gauge can handle a range of resistance.
If there is no practical way to make the 4th gen EVAP system work with a 3rd gen car, what is the next best option? I've read about some people leaving the stock 4th gen charcoal canister in place and having it in constant vent mode. If I were to go this route, can anyone tell me specifically what has to be modified or done to the 4th gen tank and system?
I'm installing the plastic tank on my '91 TPI and am running into the same confusion. Lots of info out there, but the threads seem to go in every direction.
I'm installing the plastic tank on my '91 TPI and am running into the same confusion. Lots of info out there, but the threads seem to go in every direction.
Yup. There was no practical way to hook it up since my harness wasn’t made to accommodate the EVAP. Just leave the charcoal canister assembly connected to the gas tank and forget about it. It’s probably still a better system than what the car came with. You shouldn’t smell any gas.
If you run the wires from the front of the car to the back you can make the evap work like stock with the TPI system, it's a matter of want. It's not hard, just have to put the work in
If you run the wires from the front of the car to the back you can make the evap work like stock with the TPI system, it's a matter of want. It's not hard, just have to put the work in
Any additional info on this?
I'd like to remove as much as possible from my engine bay if I can, but this tank swap has already become a huge project for what was supposed to be a "direct swap"
Yup. There was no practical way to hook it up since my harness wasn’t made to accommodate the EVAP. Just leave the charcoal canister assembly connected to the gas tank and forget about it. It’s probably still a better system than what the car came with. You shouldn’t smell any gas.
As far as the lines, you'll need 2 EFI adapter fittings that snap onto the plastic feed and return lines on the factory 4th gen pump set up. I used 2 of these at the tank, and 1 on the engine fuel rail: https://www.jegs.com/i/Russell/799/640853/10002/-1
These fittings convert the factory fittings to 6AN, so you can use braided line from the tank to the engine, and also for the return line. Or, you can use a combination of braided and 3/8" hard line for a more factory style set up (probably longer lasting too). What I did was I made a new metal hard line that runs from the back of the car to the engine bay. I used the old one as a template. I also kept the factory style fuel filter. Once I bent the line to shape, I brought it to a hydraulic fitting store and had them flare each end with 37 degree flares with tube nuts on the line. Remeber, the AN fittings are 37 degrees while the standard brass fittings you can buy at a parts store are 45 degrees. They are not compatible. If you want to use hard lines for part of the fuel system but have no way to put a 37 degree flare on the ends, you can instead use AN compression fittings that will adapt a 3/8" hard line to AN, but this is the less prefereable way to do it.
You can use the factory style fuel filter. For the return line, just plumb a T block into the fuel line after the filter, and run another line off of it back to the return nipple on the fuel pump assembly. The regulator is built into the fuel pump, so, once the fuel pressure hits 58psi, the regulator in the tank opens and the excess fuel returns to the tank.
If your fuel guage is 0 to 90 ohm (which most are), order a fuel sender for a 1998 V6 Grand Prix, which used 0 to 90 ohms. The fuel sender in the 4th gen tank does not work from 0 to 90 ohms and will not operate the 3rd gen guage properly.
For the return line, just plumb a T block into the fuel line after the filter, and run another line off of it back to the return nipple on the fuel pump assembly.
Ugh. More confusion. Thanks for sticking with me here.
My understanding was that there are 3 ports on top of the fuel sender in the tank - Feed, Return, EVAP - and three lines on the body of the car. Why is the T-block necessary? Maybe I need to go back and take a closer look.
Also, I had read that there was a fuel pressure regulator built into the rail on the TPI cars. I wanted to keep that one and not use the one in the tank. I just pop out the one in the sender unit then, correct?
Sorry for all the questions guys, but this is really not very clear and I've not found a (complete) step-by-step guide anywhere yet.
The T block. 3rd gen has the fuel pressure regulator on the engine requiring a return line. The 4th gen has the regulator in the tank with the pump. The fuel filter is in the same location on both generations. On th 4th gen cars the return line Tee's out just after the filter and goes back to the tank. This means only one fuel line going to and into the engine bay also making the return line a couple of feet vs the entire length of the car.
On my car, when I put the plastic tank in I replumbed it to do exactly what I want. I have the fuel filter and T directly in front of the tank. After the T it's only the feed line going up to the engine bay.
I had a complete donor car. I was unsure what to do about the evap system so I left it in place and wired it up. I also opted to use the 4th gen gauge cluster. I found out not long ago that the serial data wire going to the gauges has something to do with the evap operating, pure luck on my behalf.
I used stainless hard line and parts store fuel line repair parts for the plastic and fittings.
I'd like to remove as much as possible from my engine bay if I can, but this tank swap has already become a huge project for what was supposed to be a "direct swap"
I don't understand what there isn't to understand? The 4th gen put the charcoal canister on the tank instead of the engine compartment. There is a purge solenoid on the tank and there is one on the stock 3rd gen canister. You need to run the wires from the front to the back to work the purge solenoid, it's the same equipment, just in a different place. How you get the wires run back there is up to you and is limited to your imagination. The 4th gen ran them inside the car through the fuel pump power bulkhead, and is very similar in shape and size, so much so that you can put the 4th gen one in the 3rd gens stead if you like. Then the only other thing is the vacuum source, you'll need to hook that up to the intake and the 4th gen tank
There is a purge solenoid on the tank and there is one on the stock 3rd gen canister. You need to run the wires from the front to the back to work the purge solenoid, it's the same equipment, just in a different place.
In all the threads I've read through on tank swaps, you're the first person to mention the purge solenoids being the same. I understand now. Thank you.
Sorry, I did not realize you were not running tpi. I integrated the wiring when I did my swap. There is a pressure sensor on the sending unit, plus I am not an expert on the evap system. I was unsure about what information the pcm required so I left those items in place. I believe the charcoal can is for when the car is off because there is also a solenoid close to the throttle body. The evap line from the tank goes to that solenoid and I believe that engine vacuum pulls fumes from the tank. The solenoid at the tank probably let's air in and the charcoal filters the vent when off. I am not sure if it is the same as a tpi, but it could be.
04-10-2019, 08:49 PM
