Traced the fuel-return problem (and high fuel pressure?) in my '70 Charger to the big vapor separator that runs along the right side of the trunk, up over the wheel well.

The four vent lines from the vapor separator to the fuel tank are fine, and separating the fuel return line from the vapor separator allowed me to verify that the fuel return line (that leads to the engine) is OK. But the line leading up into the vapor separator is clogged. The outlet from the vapor separator up front is thus deadheaded, allowing fuel pressure to build up to like 9 psi- and when you shut off the engine it takes hours to bleed back down.

I haven't been able to locate a replacement part for the vapor separator- all internet references point to the little vapor separator up front. That's not what I'm talking about.

If I can't unblock the line (plumber's helper?), I was thinking of just using one of the fuel tank vent lines (that go up into the vapor separator) for the fuel return, and tee the extra line coming from the tank to one of the other three. Has anyone done this? Any ideas for unblocking the vent line?

The Mopar part number is 3404365

Good luck finding one though, it's California only, Charger only, my google fu couldn't find one.

Well, that explains it. N95 on the broadcast sheet.

Illustrated in the B body shop manual, didn't know it was CA only. I'll take this in trade for all the rust the car does not have.

I've run a cable tie 30 inches up the blocked vent and no joy- so looks like the bypass option.

Now a Google search that includes this part number now comes back with a link to this thread!

Whats the problem with the car? All others ran without that tank and some with no return at all.

1970 California Only ECS info for reference.

https://www.allpar.com/threads/fixing-1970s-and-1980s-fuel-evaporation-control-systems.229057/

To bypass the ECS system I think a vented gas cap is all you would need as the ECS cars have a special for those cars non-vented fuel cap and fuel tube combo. I think I would leave it functional and fix it ,assuming it needs fixed. I'm not seeing how a vapor return line gets clogged up though???

The vapor separator tube is just a tube with rubber lines inside it. Not really a wear item.

Interesting reference. I guess the vent line to the engine is connected to the extra nipple on the cap on the valve cover, except in 440 and Hemi engines, where it ran to that black-can vapor separator above the fuel pump?

This car was originally a 318 but has been, ah, upgraded.

Problems are hard starting (cold or hot) and running poorly- shudders and pops. Fuel pressure is 9 psi and I think the clogged vent line is why it is so high. Also plan to replace the distributor drive gear as timing at idle is erratic.

I think the ESC system and the black vapor separator can above the fuel pump are two separate systems?

ECS equipped cars have a 3 nipple valve cover breather with the larger hole going to the air cleaner housing and one small tube goes into the carburetor top (unique to the ECS cars?) and the other small one goes to the vapor catch/return line on the passenger fender apron. That small hard line should not have any liquid fuel going inside it as it would also be capable of dumping gas down the breather hole in the valve cover and you don't want that. It's just a way to vent the gas tank vapors into the engine and not letting them escape into the atmosphere via the normal vented fuel gas caps.

Check out the engine pics in here with the 3 nipple breather that was first used on California ECS cars and everything in 71.

https://www.moparaction.com/2020/01/15/1971-hemi-engine-detailing/

I have N95 on my 70 AAR. There are four tubes that come off of the gas tank that go to the separator in the trunk you are talking about. The line that goes up to the front from the separator attaches to the three nipple breather on the engine. It does not go to the fuel line separator. This is from memory so check the service manual.

Correct, I also have the N95 so called emissions all still on my 70 Charger R/T S.E. with a locking gas cap but have never had any pressure building issues.

Noodled this overnight and it makes sense- the four lines from the tank vent vapor to the collector in the trunk, which then collects it (from the highest point) and routes it to the thingy on the valve cover (which I then have the wrong one of). The net effect is to collect vapor from the four corners of the tank and feed it to the carburetor(s).

Think I figured it out- this car was built as a CA-spec 318, so no vapor separator above the fuel pump and no fuel return line going back to the tank. It would have only the fuel line and the smaller line going from the valve cover spigot to the CAS thingy in the trunk that is attached by four vents to the tank. I pulled the valve cover spigot from the 340 I took out and indeed it has three ports. The hard line probably angled up when it entered the engine bay to get to the valve cover, and I must have bent it down in the direction of the fuel pump vapor separator before I installed the Hemi.

But of course the 340 wasn't original either, so who knows how it was hooked up.

The old fuel tank didn't have a return line attached to it, so that was a red herring. But the spigot is there, and thankfully the new tank has one too.

So the thing to do is run a third line from the fuel pump vapor separator to the tank, and attach the vent line to a port leading the carb- I'll probably tee it in with the PCV hose, since I don't have a three-port spigot to fit a Hemi valve cover.

Per the shop manual the fuel pump vapor separator is intended to help prevent vapor lock. But if things aren't hot enough to vaporize the fuel, the separator fills with liquid and the pump shoves some of it through the vapor orifice back to the tank. Disconnect the vapor outlet and crank the engine and you get gas, gas, gas. At least I did!

Thanks to all for the input.

I suspect the small black canister that goes above the fuel pump is also just a vapor vent and not a fuel return line?

https://www.forebodiesonly.com/forum/threads/fuel-filter-vapor-separator-location.

https://www.forbbodiesonly.com/mopa...te-as-factory-did-or-dont-bother.269506/


The next question is how that return line goes to the back of the car and how does it connect back to the gas tank or vent tube?

Routed the "vapor" outlet from the black vapor separator to a (new) fuel return line that goes to the lower (smaller) spout on the tank, and routed the existing line from the trunk vapor separator up to a hose that tees into the hose leading from the PCV valve to the air cleaner.

Fuel pressure maxes out around 6 psi and bleeds down promptly when the engine is shut off. I think I fixed it.

I also learned not to unplug the return-line spout on the fuel tank when the tank is 3/4 full. I think that was the most gas I ever spilled on myself.

I hope you mean you ran the line from the crankcase air cleaner filter nipple to the fuel vapor separator tank.

Just the way it reads. I don't have an air breather to fit these valve covers.

Then you have it plumbed totally wrong. The fuel supply and return are a complete system of its own. The ECS system with the vapor tank is a system of its own. They do not share any of the same components except the fuel tank itself. Period.

i have to agree with this. ^^^^^^^^^^^^^^^
i'm thinking that if the vapor tank is plumbed into the fuel line, it will eventually get gas in it.
i may be wrong, and it wouldn't be the first time. or the last........

You are right. The way he has it the return off the fuel separator at the fuel pump area is going to the vapor tank which is wrong, wrong, wrong. That line should go direct to the return fitting on the sender and dump back into the tank. The ECS tank uses 4 ports on the tank for vapors. The other line on the vapor tank goes to the crankcase vent filter on the valve cover. At no time should that part of the system be used for raw fuel supply or return. The FSM clearly shows the two systems and their respective plumbing.

if my foggy old memory is remembering past the cobwebs, when that system first came out, wasn't there a warning about filling the tank up a bunch past the hose nozzle "click off" because gas would migrate into the canister and ruin the charcoal filter media ?

That's how I had it initially. This thread has been about me correcting it. What you describe as the correct configuration IS how I have it now.

Agreed, one of the first things I eliminate is added misery of emission equipment.....