Little Assistance. Fuel Tank Lines. 72 Roadrunner

Posted By: Pyper70

Little Assistance. Fuel Tank Lines. 72 Roadrunner - 07/31/13 07:40 PM

My buddy brought his 72 Roadrunner by today so I can help him along...I am surprised it is running to be honest. So many things wrong with it. He didnt get get a FSM so I have nothing to go off of for the Fuel line supply/return. I am shocked to say the least. He showed up with fuel pouring out of the tank area. I assumed it was the fuel sending unit seal but that component is on the passenger side of the fuel tank. I let it cool down ans I crawled underneath and the first thing I see is an alligator clip just gripping the gas tank loosely on the passenger side. Next....I drew a picture of how the lines are plumbed and how I think the lines should be plumbed. In Figure A where is says "atmosphere" its actually a fuel line, 24 inches in length and zip tied around the top shock tower and then just hanging out. Is figure B correct? Anyone have a diagram showing the correct emissions and fuel layout of the vehicle?

Car: 1972 Roadrunner, 440 4spd

Attached picture 7796895-HP0113.jpg

Posted By: Challenger 1

Re: Little Assistance. Fuel Tank Lines. 72 Roadrunner - 07/31/13 07:57 PM

I have done it both ways in the past, have used the vent line as a return. Didn't do anything different to vent the tank and it vented and ran hard like that for 6 years.

Your second drawing is correct and is how both of my cars are now. Vent line needs to windup in the engine compartment at the top of the engine.

Posted By: Challenger 1

Re: Little Assistance. Fuel Tank Lines. 72 Roadrunner - 07/31/13 08:00 PM

They stopped going in the trunk with the vapor separator in 71. 72 was underneath.

I have never used the return on the sending unit as a vent, no way that'll work well.

Posted By: Pyper70

Re: Little Assistance. Fuel Tank Lines. 72 Roadrunner - 07/31/13 08:03 PM

The way figure A is seems hokey to me....its just 24" of fuel line...zip tied around a shock mount....and underneath the rear axle hump...its just hanging there at the same level as the fuel tank...

Where exactly does the vent line go at the top of the engine? I don't think I have seen that before

Posted By: Pyper70

Re: Little Assistance. Fuel Tank Lines. 72 Roadrunner - 07/31/13 08:07 PM

Quote:

They stopped going in the trunk with the vapor separator in 71. 72 was underneath.

I have never used the return on the sending unit as a vent, no way that'll work well.

I am just going into it with past knowledge of a 70 A Body and a 70 B-Body, both California cars with the galvanized tube on the passenger wheel well in the trunk....

If 72 was underneath....where to do they attach? It surely can't be a hose just hanging there ready to puke fuel

Posted By: MoparMarq

Re: Little Assistance. Fuel Tank Lines. 72 Roadrunner - 07/31/13 08:11 PM

The line you have labelled "to trunk", I believe actually goes to a vapor line to the charcoal canister in the engine compartment. The charcoal canister is mounted far forward on the passenger side inner fender, almost up against radiator yoke.
Although with 440, it may be different - mine was 400-auto-CA emissions. Mine also didn't originally have the return line, though 440s did have the fuel/vapor separator mounted near the fuel pump, with the 1/4" return line, per the FSM.
If the charcoal canister has been removed/tossed, the fuel vent line should vent high enough to avoid liquid fuel coming out, though I might avoid the trunk, if possible. FSM says the tank should have pressure/vacuum relief cap.

Member 72RoadRunnerGTX might know for sure.

Posted By: Pyper70

Re: Little Assistance. Fuel Tank Lines. 72 Roadrunner - 07/31/13 08:38 PM

Alright...I went and checked the car....There is a special place in hell for people who sell a car online and don't hook up any of the provisions.

I found the fuel vapor canister. The "Fuel line" is "connected" I will have to verify that line tomorrow. The other three lines are just hanging out zip tied to each other and dumped by the rear of the manifold.

Attached picture 7796963-VaporSeparator.jpg

Attached picture 7796963-VaporSeparator.jpg

Posted By: MoparMarq

Re: Little Assistance. Fuel Tank Lines. 72 Roadrunner - 07/31/13 09:19 PM

Quote:

Alright...I went and checked the car....There is a special place in hell for people who sell a car online and don't hook up any of the provisions.

I found the fuel vapor canister. The "Fuel line" is "connected" I will have to verify that line tomorrow. The other three lines are just hanging out zip tied to each other and dumped by the rear of the manifold.

According to the FSM regarding the canister...

The outboard-most line should be labelled on canister as "carb bowl" and connects (un-teed into anything else) to the carb bowl vent.

The next line toward the fender should be labelled "fuel tank" and should be connected to the fuel-vapor separator line from the fuel-separator that is mounted on the rear shock cross-member by the tank (NOT the fuel-vapor separator by the fuel pump). This line is not teed into anything else, either. (this is the one that goes toward the aft part of the passenger inner fender to where the steel vent line meets it at the upper surface of the frame rail.)

The next line toward the fender should be labelled "PCV" and is teed into the unported vacuum line from the manifold/carb to the PCV valve.

The last, outboard-most line should be labelled "dist (something)" and is teed into the the ported vacuum line from the carb to the distributor vacuum advance can.

Other than the "fuel tank" vent line, these other three lines should travel from the inner fender near the shock tower across the top of the valve cover to their respective locations/vacuum lines.

The FSM is somewhat incomplete in its description of the fuel and emissions systems. My car had 400-auto, so a fuel supply line and vent line from the tank to the front. The FSM doesn't speak to it, but I assume 440 cars had three lines from the tank to the front - fuel supply, vent, and 1/4" fuel return. If this car has only two, maybe a PO took the return line out.

Posted By: Pyper70

Re: Little Assistance. Fuel Tank Lines. 72 Roadrunner - 07/31/13 09:37 PM

Many many thanks for that MoparMarq...

if there is no vapor separator at the rear close to the tank...should I get him to buy one?

If there are only two lines (and I will check that tomorrow) can I just hook up the return line from the fender mounted canister into the return line of the fuel sending unit?

If the previous can be performed...what can I do with the 4-port emissions manifold on the rear shock cross member?

Posted By: MoparMarq

Re: Little Assistance. Fuel Tank Lines. 72 Roadrunner - 07/31/13 11:21 PM

Quote:

if there is no vapor separator at the rear close to the tank...should I get him to buy one?

If he can find one, yes. But I don't think they are repro'd. And I don't think they were in production 'til '72, but not sure. Tanks were changed in late '72. So probably JY hunting he will go, late-'72 to '74 B-body. OR, cobble one together with lots of 5/16" steel t-fittings, 5/16" fuel line and hose clamps.

Quote:

If there are only two lines (and I will check that tomorrow) can I just hook up the return line from the fender mounted canister into the return line of the fuel sending unit?

I wouldn't. With a full tank, the return line will be submerged. On a hot day, as the fuel expands, liquid fuel will be forced out the vent into the canister.

Quote:

If the previous can be performed...what can I do with the 4-port emissions manifold on the rear shock cross member?

For some reference, here's a thread with some discussion and pics...

Looks like the '73-'73 E-body F/V separator back at the tank is the same piece as in my '72 RR. Maybe not as hard as thought perhaps to find one...

Challenger_1 is a knowledgeable guy, so he's worth a listen.

https://board.moparts.org/ubbthreads/showflat.php?Cat=0&Number=7333957&Main=7330082

Posted By: moparmarks

Re: Little Assistance. Fuel Tank Lines. 72 Roadrunner - 08/01/13 01:14 AM

71 and the first part of 72 the vapor tank is in the back of the left rear fender well. Sometime during 72 production they moved the tank to the shock cross member. I have a couple 72B's with the fender well tank.