What izzit?

[Ascaris]

There is a very small diameter, clear plastic tube that comes out of the center tunnel, through the firewall, and up into the engine compartment where it just ends (not connected to anything). Anyone know what it is for? There is no corresponding hole in the new firewall I am installing and I am wondering if I want to drill one or just let it go.

I have a '74 1.8L. Thanks!

[jmcleod]

it's not a fuel return line, izzit?

[John Rogers]

I'd try taking an air hose and blowing some low pressure air through it to see where air comes out? Might be important? But at any rate, let us know.

[Doug M]

I think it might be the fuel tank vent line that runs back to the carbon can

[Ascaris]

The fuel tank vent line seems the most likely, but why run it the length of the car? It is very small in diameter (1/8" OD maybe 1/16" ID) so not much good for fuel, etc and a lot of friction resistance even for air. It could also easily become clogged. I'll let you know if I figure it out.

[mejulihn]

I believe it is the vent line that connects to the charcoal cannister in the engine compartment. However, I do not know if the charcoal can came as part of they smog equipment on a '74 1.8. My '74 2.0 did not have one as I recall (but it could have been removed by a PO).

[Dave at Pelican Parts]

It could possibly be the vent line.

All US-spec 914s were originally delivered with charcoal cannisters--it was required for all of them. (Actually, I talked to one owner of a 70 that didn't have one, but the Certificate of Authenticity from the factory said it did have one.) In my two 74s, one had the charcoal cannister up in front by the fuel tank (the 2.0), and one had the cannister on the rear wall of the engine compartment (the 1.8). Not sure why the change, and I've heard from people with 1.8s that had cannisters up front.

I don't remember the routing from the 1.8, but the small vent line could have come through the tunnel...

The general theory appears to be that the engine cooling fan pushes air into a hose, through the cannister, then into the air cleaner. In cars with front-mounted cannisters, these two air lines run through the left-side rocker panel from the engine compartment up to the front compartment. A third, smaller hose connects the cannister to the fuel tank expansion chamber. This carries fuel vapor into the cannister. I presume the flow caused by the other two hoses carries the fuel vapor into the intake to be burned, but I don't really know.

Anyway, this third small hose must get from the tank to the cannister somehow. On cars with the rear-mounted cannister, it may run through the center tunnel or possibly through the left-side rocker panel. Check for hoses there and check for spots where the cannister may have been mounted.

--DD

[Ascaris]

There is a label on the drivers side of the engine compartment for the charcoal canister, but not canister in sight. The tube in question, however, is led up through the passenger side of the engine compartment sheet metal (with it's own little gromet) to end just below the battery tray.

I did manage to get the firewall welded in this weekend and probably will just drill a hole (a little higher up this time to prevent water/rust problems) and put it "back where it came from". Much easier to leave it original and do it now than to find out I want it at some later date.

[Dave at Pelican Parts]

That sounds suspiciously like one of the plastic "hard line" fuel lines that go through the center tunnel. Or rather, one of the other "hard lines".

There is a second set of "hard lines" that go from the fuel pump to the fuel rail, and from the fuel pressure regulator down to the 'Y' fitting that goes to the return line in the center tunnel.

--DD

[Ascaris]

Doesn't seem to be a fuel line. Too small in diameter and nothing runs out. It did exit the firewall right next to the two fuel hard lines though.

[randyle]

I have a 1975 914, 1.8. On my car, the line goes from the expansion chamber on top of the gas tank to the charcoal canister in the engine compartment. It is actually a part of the smog system. The charcoal canister has one large hole on one end, and one large and one small hole on the other end. You need a small piece of fuel line (or something similar) to attach the plastic line to the charcoal canister - it does not attach directly. Dave Darling has a vacuum hose diagram for the 1.8 L-jet that shows this line.

[dave914]

Perhaps It was me that Dave Darling mentioned as the guy who has a US spec 1970 914 with NO vapour recovery system. My car is an early build (1969 date) 1970 year model My car has the US EPA door post srticker. The factory wrote me and stated that my car left the factory with US equipment. Yet I have no carbon canister, no hoses, nor the holes in the panels for the hoses. No take off on the fan house, nor port on the air cleaner. This car was likely a factory mix up. One other interesting thing is that the muffler heat shield that is spot welded under the trunk floor, is actually screwed down on my car, all others I have seen are welded on. This made life easy for my when I re-painted the under side of the car, it just unscrewed.
One thought on your unknown hose, could it be an AC condensation line??? If you had AC in the car at one time, there should be a big cut out in the floor of the front trunk for the hot cool. good luck dave

[Dave Bell]

randyle has the right answer I believe. I too have a 75 1.8L that I recently purchased and just had to have smogged in CA. The old charcoal canister in the car had to be replaced and that little clear plastic tube runs from the expansion chamber on top of the gas tank to the charcoal canister in the engine compartment just as randyle describes.
Just to check it out to make sure, I ran some air, (me blowing into the gas tank end, yech!).. while my 9-year old son checked the air coming out of the canister end of the hose. We switched places, (brave little boy), and double checked that we had both ends of the same tube.

Randye is also correct that the tube does not attach directly. I have rubber tube fittings on both ends to mate the tube to tank and canister.

Hope this helps.

[Ascaris]

Dave, where is the charcoal cannister located? I don't seem to have one (although there is a label for one on the inside of the engine compartment on the drivers side.

I was re-running all my lines yesterday and the mystery clear tube follows the fuel lines up through the engine compartment sheet metal on the passenger side. Has it's own little angled grommet, just like the fuel lines.

I'm going to drill a new hole in the firewall and put it back "where it was", but would like to confirm what it is - even if I don't use it.

[Dave Bell]

On my machine, the charcoal canister is located in the engine compartment, on the passenger side, just to the left, (as you look from back of car to front) of the battery. I'm at work right now and can't look at it, but the canister is about 6-8 inches long and about 4 inches in diameter and has the three hose connections that randyle described, one large connection on one end and one large plus one small connection on the other end. The small connection is where the clear tube running from the fuel tank vapor area attaches. I would have to check again where the other tubes run but Dave Darling had a pretty good description.

If you had a canister in your engine compartment now, you could not miss it. I don't know how it was originally mounted but mine is sloppily lashed to something else in the engine compartment... can't remember what right now. Perhaps it was originally mounted toward the driver's side as indicated by the label on your car.

[Dave at Pelican Parts]

Dangit, I *gotta* remember to ship those JPEGs to my home computer! That way I could check them, and even send them out when they're needed... (Yes, I forgot again. I can e-mail you Pete Klager's diagrams on Monday if I remember.)

I don't know if the setup that was in my 1.8 was the factory one or not. I wasn't paying a lot of attention to such details when I owned it. However, I kinda remember the cannister being held onto the rear firewall by a metal band, kind of like a hose clamp.

DOH! Factoy parts book. Here we go. The diagram is labeled "Ab Mod. 74", which I think means after 1974, or 74 and later. The 2.0 is an early model year 74 (built 10/73) but then again I think the 1.8 was as well.

Anyway, the cannister was located on the rear wall of the engine compartment, over toward the passenger side. It was somewhere between the centerline of the car and the right-side hole where the roof latch sits when it's in the trunk. It was fairly high up, and was almost certainly attatched to the car's body and not to the rear vertical "engine tin" piece.

Hope this helps. If you need the part numbers I have listed here, give a yell.

--DD

[Ascaris]

Thanks Dave, that is exacly where the mystery tube was heading. Since there is nothing in place for it to meet up with, I must assume that it was removed sometime by the PO. I'll take a look later tonight when I get home.