-----Original Message-----
From: Bruce Leggett
Sent: Wednesday, March 20, 2002 5:46 PM
To: 'cgshawaii@netscape.net'
Subject: RE: Vanishing MPGs, look for leaks (longish)

On my '75 CSi, this under-filler neck nipple wasn't connected, so I looked on a junkyard 2000CS and found a specially formed piece of tubing that went from the nipple down to a hole that exited the trunk just inside of the rear bumper. I don't have a vapor recovery system (could have been left off post-restoration ...)

Cheers,
Bruce

 

---

-----Original Message-----
From: cgshawaii@netscape.net
Sent: Wednesday, March 20, 2002 2:14 PM
Subject: RE: Vanishing MPGs, look for leaks (longish)

Julian: I suspect my coupe of this also, and "of course" I have occasionally the hydrocarbon reek in the car. The secondary cause of the smell is usually a trunk lid gasket that isn't sealing, allowing the ventilation system to draw air (fumes) from the trunk into the passenger compartment. Deal with this as you may; CNPR (and probably Maximilian, etc) will sell you a new trunk gasket.

The primary cause is leaking gas, from the sender o-ring, tank seam, tank, or hoses. Let's look at these one by one.

To check the sender o-ring, fill or nearly fill the tank, remove the floorboard over it, and rock the car side to side. If you see wetness at the sender, the gasket is bad or the sender isn't seated correctly. The o-ring can be replaced by a GM transmission o-ring. Make sure it seats nicely when you reinstall the sender.

The tank sits on a strip of open cell foam, on the body. The foam retains water and causes rust along/near the tank seam. Look for wetness when the tank is full or nearly so. Tanks can be fixed by soldering, brazing, or welding, but it's hard to find someone who will do this for you. The tank must be empty and filled with noncombustible gas, or it's a bomb waiting to go off.

Hoses leak, especially old OE hoses, which get brittle with age, and crack, usually near flex points and/or near connections. You can easily and inexpensively replace the line from the sender to the metal fuel tubing.

There is supposed to be a vapor recovery system on the car, with a plastic tank above the right rear inner wheel well. The plastic tank is connected via a small flex hose (replace it) to a steel nipple on the underside of the tank filler. Look for the nipple in the trunk, between the metal filler tube and body. Further, the plastic vapor canister is connected to the air cleaner housing by another plastic tube which runs through the passenger compartment. Check this by first finding it, plugging one end, and applying gentle vacuum (Mityvac brake bleeder works well) or gentle pressure (tape a inflated rubber balloon on) and see if there's a leak in the line. BTW, when finished, make sure the vapor line is actually connected to the air cleaner housing up front.

Sounds like you don't have the vapor recovery system, or don't know where to look for it. If it's missing, you'll be leaking gas from the vapor recovery nipple into the trunk when you fill, and when the car rocks and gas sloshes up into the filler neck. The ventilation system does the rest.

JOsante@aol.com wrote:

Dear Coupe Group:

I know E9's have never shined brightly for their frugality when it comes to fuel economy but I'm pretty sure that I'm losing 1/8 of a tank overnight and was wondering if any of you had a similar occurrence come your way AND had found a FIX. It used to be that upon parking the car it would stink of gas like there was no tomorrow but that is basically a thing of the past. The one moment I do smell gas nowadays is whenever I gas up and not necessarily does it have to be a fill up for this to happen. Carbs have been replaced and are in tune, also a leaky fuel pump -- hence the smell back then -- and pretty much nothing else. I suspect the fuel sender gasket AND/OR the hose that connects the tank filler to the tank BUT since I believe that the old "if it ain't broken don't fix it" adage applies to a car this age way more than on other items, I wanted to check if anybody else had indeed had this "vanishing gas" syndrome happen to them. There are no visible leaks, and like I said before, no smell except for right after gassing up

Best and TIA,
Julian Osante
'71 3.0CS

PS; the gas tank does have a vent line that vents to the outside to the outside of the car; I assume this is normal BUT has anybody ever retrofitted a vapor return canister/system onto these cars?

 

-- Charlie
BMW CCHawaii