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-   -   '79 fuel line hookup from gas tank - need a sanity check (https://www.rx7club.com/1st-generation-specific-1979-1985-18/79-fuel-line-hookup-gas-tank-need-sanity-check-1158377/)

travm 08-18-22 09:27 PM

'79 fuel line hookup from gas tank - need a sanity check
 
Hey guys, I recently became the owner of a '79 and I'm slowly making my way through it fixing what needs to be addressed. I dropped the fuel tank with the intent to replace the sketchy looking fuel lines and discovered that not only were the lines hooked up incorrectly but I was also missing half the stuff that's supposed to be back there. The tank return line was hooked up to the fuel pump feed, while the tank supply line was vented to atmosphere, and the check valve and check/cut valve were straight up MIA.

The supply line was plugged up pretty bad but I managed to get it cleared, and have a new check/cut valve on the way. I was hoping someone could give me a sanity check on how everything should be hooked up since the factory diagrams aren't 100% clear. Based on the attached photos, this is my understanding:

a) The tank line closest to the front (leftmost line in the photo) is the fuel return line. This connects directly to the middle of the three hardlines in the photo (photo is facing towards the front of the car). Tracing this line forward to the carb, this appears to check out.
b) The second tank line from the front (the largest line) is the fuel supply line. This seems correct as this tube goes the furthest down to the bottom inside the tank. This connects to the largest, leftmost hardline in the photo (not the one that crosses over the other two). From there, in order, it looks like it should go: fuel filter, then fuel pump, then check valve, then to the next hardline further up which leads to the fuel supply on the carb.
c) The third tank line from the front goes to the check/cut valve. Per the factory diagram, tank line goes to one of the horizontal lines on the valve, other horizontal line gets capped, and the vertical line vents off. This is where the diagram gets unclear, but I'm pretty sure it vents off to the hose sticking out of the frame rail all the way to the left in the photo.
d) The rearmost plastic line is the tank vent. This connects direclty to the rightmost hardline in the other photo (the one that crosses over the other two) and traces back to an emissions valve in the engine bay.

Does this all sound correct? I did search but there still seemed to be confusion on a couple of items on the SA cars specifically. Thanks in advance for the help!

https://cimg8.ibsrv.net/gimg/www.rx7...b59d6ebb1.jpeg
https://cimg9.ibsrv.net/gimg/www.rx7...1f0cb47ab.jpeg
https://cimg7.ibsrv.net/gimg/www.rx7...991e902c01.png
https://cimg8.ibsrv.net/gimg/www.rx7...dd8f9b1542.png


KansasCityREPU 08-19-22 11:40 AM

I just went through this process on a 1979. I used the lower image you have posted.

Hook up the obvious based on the diagram first. Once I studied the diagram enough, it was pretty clear where things went. I purchased Gate 6mm and 8mm hose on 25' roles on Amazon because I'm doing two 1979's. Much cheaper then the auto parts stores and I'll have extra for other hoses on the cars.

https://cimg0.ibsrv.net/gimg/www.rx7...06c0529fb5.png

travm 08-25-22 06:03 PM

Thanks for the additional diagram! This adds enough clarity that I've got it figured out now.

I actually found fuel hose on McMaster-Carr for cheaper - it's rated for 50 psi which should be more than enough, correct?

esox 09-23-22 12:08 PM

I'm sure you've got it figured out by now by yes 50psi will be plenty. You've got a low pressure fuel pump since it's a carbed so it only outputs around 5-7psi of fuel pressure. Also some people run a filter both behind and in front of the fuel pump, but you only need one and in between the tank and pump is the way to go

travm 09-27-22 11:13 AM


Originally Posted by esox (Post 12534728)
I'm sure you've got it figured out by now by yes 50psi will be plenty. You've got a low pressure fuel pump since it's a carbed so it only outputs around 5-7psi of fuel pressure. Also some people run a filter both behind and in front of the fuel pump, but you only need one and in between the tank and pump is the way to go

I did get it all back together but thanks for following up! Stoked on how helpful this community is so far and glad to be a part of it. I've just got the one filter in the factory location before the pump as you said, good to know that's adequate.


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