pugtech

Fuel drips from the right rear of our 1980 US Manual after a fill-up for about an hour then stops until the next fill-up. Any tips on where to start?

Thanks...Scott

Normy

Yes. Stop filling your car first thing in the morning when the fuel and the car is cold. My '85 S2 drips fuel from the cap as the day heats up if I do this. Thermal expansion.

FotoVeloce

I don't know if this is the same issue, being such different bodies cars, but when I first filled up my 964 it dripped feul for about 1/2 hour in front of the left-rear tire where the evap canister is. Turns out the check valve atop the fuel tanks expansion chamber was knackered (in what way I have no idea, new and old seemed to sound the same when rattled) and allowed raw fuel to be drawn into the evap canister, filling it and then the fuel would drip out of it's overflow hole. Plus on some occasions it would suck raw fuel into the intake and run like a**.

$30 for a new expansion chamber check value and it's been 10,000 trouble free miles and I can fill the tank any time I want (hot or cold) all the way to it's 18 gallon glory.

LT Texan

There is a hose that connects the top of the main portion of the tank to the section that is directly below the filler neck. This is so air is not trapped in the main part of the tank. the hose passes thru the unibody.

Mine was cracked and leaking. Only leaked when 3/4 full or more.

Dan Perez
78 5 speed
Old Bugger

CaseyH

I have this same problem. It only happened to me one time -- the first time I filled up. Ever since I just don't fill up all the way and it doesn't leak. I'd obviously like to get it fixed one of these days but I was never really sure what the problem was.

BrianG

+1

Very common...... you can get into there by pulling the fender liner in the wheel well.

FlyingDog

It's either this or the sealing ring in the top of the tank is leaking. The vent hose is the more likely suspect. Mine does it, especially if I park with the nose uphill. I left a hole in another 928 owner's driveway the day I discovered this...

checkmate1996

Does anyone have a part number for the two areas in question? Mine did this for a while, and then STOPPED?

Daniel Dudley

It is hard to get a good seal on the fuel sender O ring, because you can't get a wrench on the ring. bought a PVC T fitting that fit the ring and cut slots in it to correspond to the little ''fins'' on the ring. I also cut slots to clear the fuel hoses. This ''wrench'' makes it easy to tighten the fitting and cinch down the O ring. Assuming there is an O ring.

SharkSkin

There should not be a problem with filling up in the morning and spilling fuel in the afternoon. After I went through the tank venting system I filled the tank until the fuel level was above the "unleaded only" insert in the filler neck, I went for a drive trying to see if sloshing the fuel around would find any leaks, and the system was tight.

The problem with yours could be the fill cap, sender, or any of a number of hoses. Also, the sender does not have an o-ring, it has a seal with a specific cross-section. An O-ring could work, but it's not the right part. First pic below shows the seal on the sender, second pic shows the venting and expansion tank parts for a 78(I think it's about the same for an 80). Note that items 20, 21, & 22 come from Porsche as a single length of hose that is too short to fit all 3 locations -- probably better to just use bulk fuel line for the whole job.

3000teeth

I recently dropped the tank to fix a very similar problem. Fortunately, I was able to fix it by replacing the $54 breather hose (item #11 in the diagram below , part # 928 201 194 02).

However, I got lucky for two reasons:

A) I followed Sharkskins detailed instructions (which he links to in the previous post) and didn't damage any fittings.
B) I didn't have any other damage to the tank. There are several threads in this forum around trying to fix a cracked tank, and since it's made of plastic, it's nearly impossible to fix permanently without replacing.

-T

pugtech

I believe my leak is coming from the breather hose (11) as well. I'll know tomorrow.

SharkSkin

Travis, I know where to get the original braided vent & vacuum hoses locally for anywhere from $0.50 to a couple bucks a foot for that 15mm breather... Reitmeir. He's a repair shop rather than a parts shop, but he knows where to find oddball metric stuff like this. Just make sure you know exactly what you want before going there. What he doesn't have on hand he can get in a day or two.

LT Texan

yep, mine was no. 11 too

Dan
78 5 speed