JPTL

UPDATE - To skip the troubleshooting and go straight to the cause & cure, scroll to #13.

Today was the second time that I got a strong whiff of raw gas after driving & pulling into the garage. I'll say this upfront:
The car will not be started/driven again until I find the source/cause.

The conditions were exactly the same in both instances:
After driving around town on a hot day, A/C running, fans running, I pulled into my driveway and idled for a minute or so while the passenger got out and the garage door opened. It wasn't until I pulled into the garage, shut off the engine and got out of the car that I noticed a sharp smell of raw gas. Both times it went away as quickly as it came...but I know this is a fire waiting to happen - in my garage, no less!
Both times I lifted the hood to see how strong the smell was and to ventilate things. The smell isn't coming from the engine bay...at least I'm pretty sure it isn't. I'd think that if it were I'd be bowled over by a gas smell.
Again today, I opened the hood and didn't smell the gas. I walked around to the exhaust and took a whiff. Raw gas smell coming from the exhaust...or at least that's what I think.
<start speculation> It's as though excessive fuel is being dumped into the intake during a hot idle, and instead of the engine continuing to run by starting off from an idle & burning the fuel - like at a stoplight, I'm shutting the engine off. The fuel therefore goes unburned. The confined area of the garage contains the vapors and makes them more apparent. </end speculation>
I hadn't noticed any vapors in the cabin while driving, but I'm not ruling out another broken Y connector - even though I replaced the original w/an oem back in '07. I don't recall the broken Y producing such strong, raw gas smells however and I'm not smelling anything in the cabin while driving.
I know that fuel line replacement is in high order, but any ideas as to what else I may consider & where I should start?

Speedtoys

Inspect the fuel pump/filter connections and hoses.

I had this for about..ohh..a week once, never strong enough to REALL register.

Then one day it was bad..and it was the fuel pump high side fitting.

docmirror

Start where you start, with the fuel lines. After that check the FPRs. Get a fuel pressure gauge, and jumper the fuel pump then begin the investigation with a high intensity LED flashlight.

Jerome Craig

J.P.

Three things. First replace the oem "y" pipe with a metal one from Nicole. Second, check your fuel pump area and see if you have any leaks there - like at the seam of the fuel filter or the banjo bolts at the "j" pipe. Third, when I did my intake refresh I replaced all of the fuel lines and I had no more gas smell in my garage - at all!

Jerome

Randy V

JP -

JPTL

Great advice...
..including yours, Randy. I hadn't considered the Holy Hand Grenade of Antioch.

dr bob

JP--

Fuel dribbling onto a hot engine part will boil off pretty quickly. It will also flash to flame pretty quickly...

Pull the air cleaner housing completely, so you have easy access to the fuel plumbing at the rear of the engine bay. Pull the fuel rail covers too. With engine cold, plug that switched jumper into the FP relay socket to pressurise the system, then start hunting. Since the fragrance was noticeable at the rear of the car, I'd start sniffing there. Use your fingers to test around every hose and connection. Stuff that you may not feel on your fingers can sometimes be detected by smell. If you search with a paper towel or gloves, sniff them to help find a leak.


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When you had the lastest experience, dit it follow a recent fill-up or perhaps some spirited driving that might have fuel splashing on the cap and the vent hoses at the filler neck?


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Did the intake refresh, and all the hoses -looked- good as new. Put new in anyway, and did the pump-jumpered rub-and-sniff leak detection on all the plumbing. Found just a tiny bit of seepage at the rear fuel pressure damper where the left fuel rail hardpipe connects. Not enough leaking for a dribble or even a wet feeling, not enough for a nose alone. But a quick wipe-and-sniff was enough to show there was a leak.

antlee928

Check the Y-piece connector in behind the RH side inner wheel liner where the charcoal cannister is lovated. This is oftemn the source of breakage with age and strong fuel smells will come from here. The other area is the fuel guager sender unit and the rubber seal. Again with age this will weep or leak fuel into the valley in the fuel tank in this area. It typically only occurs on full fuel tanks and you will get strong fuel smells from rear of car neaer the fule filling cap and rear inner wheel guard area. Other than that check all fuel lines staring from the fuel tank and fuel pump.

Good luck and best to get on toip this quickly for fear of combustion and fire.

Cheers

M. Requin

To me this is a red flag. "High order"? How about "survival"? If this has not been taken care of, it is your first order of business, whether it is the source of fumes or not.

namasgt

Check your Y connector, my new one didn't last very long and it had a strong smell, also check the fuel line going to the top of the fuel tank, rear trunk area under the carpet, that line could be bad.

Dave928S

When you find a problem don't assume it's the only issue ... check everything else before you regard it as problem solved.

KLVA

Also, the vent hose that runs from the fuel neck portion of the tank, thru that hole in the body to the top of the main portion of the tank...
split hoses or missing clamps will spill gas on top of the tank as the gas sloshes around...
usually fumes seap into the cabin from on top of the tank up thru the plastic sender cover above the tank in the rear cargo area...

remove the fender cover ..RR..look up to see if the larger hose going aft from the fuel neck still has a clamp or is split...

Seeing the other end is more challenging...almost have to use a mirror and flashlight to even see it....

In order to really check the other end..you must lower the tank down...

Also check the welded curved pipe that connects the fuel pump to the fuel filter
under the tank cover ...this would be the 1st thing to check

Also check the area where the strainer screws into the tank for any drips

Did you fill up the tank pretty full before/while driving it...?

That would lead me to think it was the 1st thing, that equalizing vent hose...

All these things have happened to me..the curved pipe on my 88 S4

The vent hose between the tank sides on the 79 OB and a leaky strainer on the 78 Euro at SITM

Let me know if I can help...could even come up there if need be...

Cheers, Kevin

JPTL

After describing the symptoms in length with KLVA, his prediction: a leak at a connection at either the fuel filter or the fuel pump.
I dropped the cover and the inside was telling:

Gas soaked grunge build-up.
The brass line coupling nuts at the fuel pump had loosened (copper washer shrinking after 20 years?).

The pressure at the fuel pump was causing a slow drip.
A little tightening of the nut, and no more leak.
Thanks for the suggestions here, and thanks Kevin for the pre-op diagnosis!

M. Requin

Really glad you got this sorted out, and thanks for the followup. It's good to know how these issues get resolved. And very interesting about that banjo bolt, I think a routine check on that area is in the near future for my 928, even though I have no gas smell.

JPTL

There's no doubt in my mind that a negligible loosening/shrinking of the copper and/or brass fittings at the pump must occur in all of our cars regardless of condition or miles. It should be on that checklist of inspection items unique to the 928 (along with belt tension, headlight arm linkage e-clip, etc).

For those of you new to this, it's a very easy thing to check by simply dropping the cover(at least on 87 & later cars).
It doesn't require lifting the car, just lying on the ground at the pass. side of the back bumper. Simply remove two 10mm nuts and the cover comes right off. The inside of the cover tells it all: if it isn't totally dry and looks oily or greasy, you have a leak.