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 fuel supply vs return 
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Post fuel supply vs return
I don't mean to be a chump. I'm sure this has been discussed, but on my phone search is difficult.

I'm doing a ZE into a GS swap. Is the shorter fuel hose that points out towards the passenger's side the supply? It made sense, since it only has to reach the filter.

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January 15 2014, 5:12 PM
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Location: Twin Cities, MN
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Post Re: fuel supply vs return
front of engine 1-3-5-fuel filter = fuel supply
front of engine 2-4-6-fuel pressure regulator = fuel return
---------------front bumper-----------------------

Fuel supply comes from the tank through the fuel filter into the rear (or right side) fuel rail (cylinders 1, 3, 5).
Fuel return comes from the front (or left side) fuel rail (cylinders 2, 4, 6) connected to the fuel pressure regulator.
At the front of the engine there is just a hose that connect the fuel rails.

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January 15 2014, 7:26 PM
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Post Re: fuel supply vs return
Great info, but I'm a little rawer than that. The engine's end I have down. Imagine being down to the firewall. Looking at it from the front, you have a shorter hose going left and a much longer hose going right. Can supply pictures if necessary.

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January 15 2014, 9:03 PM
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Joined: November 02 2012, 8:40 AM
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Location: Troy, VT
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Post Re: fuel supply vs return
Elli wrote:
I don't mean to be a chump. I'm sure this has been discussed, but on my phone search is difficult.

I'm doing a ZE into a GS swap. Is the shorter fuel hose that points out towards the passenger's side the supply? It made sense, since it only has to reach the filter.


Easy way of checking would be turn the key on and prime fuel pump to see what line is your supply.
The shorter hose would be for the filter like you pointed out.
I usually just leave this line and the filter in place when swapping engines
If you get a no start, then just swap lines.

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January 16 2014, 9:48 AM
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Post Re: fuel supply vs return
I'll just set the battery in place and pull the return hose. I was thinking I needed the tray to be in for some reason.

Would running them backwards damage the regulator?

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January 16 2014, 10:55 AM
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Post Re: fuel supply vs return
Elli wrote:
I'll just set the battery in place and pull the return hose. I was thinking I needed the tray to be in for some reason.

Would running them backwards damage the regulator?


Just turn the ignition on and see which line is the supply, problem solved!!

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January 16 2014, 11:46 AM
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Post Re: fuel supply vs return
Well if you look at the top of the fuel tank the left hose is the supply. I guess you could trace from there. The length and orientation of the fuel hose in the engine compartment might mislead. There are sections of hose and hard pipe before it gets to the pump.

I'm not sure the fuel pump will run with ignition just in the on position. The fuel pump should definitely run if at the diagnostic box you jumper GND to F/P and turn the ignition key to on. Just be careful and have a fire extinguisher on hand. It would be terrible to burn up one of these old cars - even worse one of their owners.

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January 16 2014, 1:44 PM
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Post Re: fuel supply vs return
Come on now... Not even necessary to get underneath the car. Turn the ignition on give it a couple cranks which maybe needed to prime the pump and there you go.
Yes it pose's a fire hazard but be smart about it and don't keep cranking and dumping fuel on the ground and don't smoke around fumes.

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January 16 2014, 4:12 PM
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Post Re: fuel supply vs return
Indeed, just connect GND + F/P and turn ignition.

Just let someone else turn ignition, so you can catch the fuel with a cloth.

Don't put it on backwards, that would mess things up. Look up how a FPR works, you'll know why not to do this.


January 16 2014, 4:32 PM
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Post Re: fuel supply vs return
I'm mid swap. the battery tray isn't even ready to go in yet. Of course it's not a huge deal, but I was thinking someone would just know off hand and I could avoid gas fumes in the same garage my furnace fires up in..... just thinking.

I'm just gonna disconnect the return side from the rail. If fuel shoots out of the hose, it's backwards. If fuel shoots out of the rail, it's fine.

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January 16 2014, 9:04 PM
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Post Re: fuel supply vs return
For the record, the shorter hose that points to the passenger's side is the supply.

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January 30 2014, 12:16 AM
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