Educate me on fuel/vacuum lines, please!

[Dooodahman]

I have the dreaded fuel smell in my new-to-me '88 coupe. It seems to be getting worse (to the point where I don't want my 3 year-old riding in the car till it is fixed) and I really want to just replace as much of the fuel lines ("vacuum" lines?) as possible. I have read every topic on here that I could find, and they all seem to be a bit over my head.

I want to get the replacement lines from our host, but I am not sure what to order. I see they come in different ODs. And I am not sure what a reasonable amount of length to get will be. From what I read on here, a good place to start with a raw fuel smell (which is what I think I have) is the lines under the frunk. So I think I should start there. I also read Grady's vacuum line thread and understand that the best method is to fix and maintain the stock system.

Also, when it comes to the tunnel lines, it appears that people are having things fabricated as opposed to buying off the shelf. I understand that the tunnel lines are the last ones to do since they are so hard to do, but taken as a whole, this project is beginning to scare me.

Am I in over my head? I really want to do this work myself and begin to familiarize myself with this car. Anyone willing to take pity on me and spoon feed me some info?

[crustychief]

Check the fill line from the gas filler neck to the tank and the vent hoses in the "frunk" and left inner fender area. I do not think it is possible to get a fuel smell from a bad vacuum line itself. more than likely it is a fuel supply / return hose or the ones I mentioned. If it is a bad fuel line it will either appear wet or will actually be leaking fuel.

[Smoove1010]

I'd take it off the road until I've isolated the cause. Minor fuel leaks can go from seepage to disaster very fast.

Check the lines under the "frunk" - there's a 4" piece of hose that connects the tank to the pump, and two hoses that connect the pump to the lines in the tunnel. You'll need to remove the bash-plate to get a good look at these lines.

I replaced the 4" line last spring when I had similar fuel smell issues. It wasn't dripping, but the fabric sheath was wet to the touch. I slit the line length-wise, and here's what it looked like inside:

This wasn't yet a dripping leak, but from the appearance, it could have become a gusher pretty fast.

Read every thread here about fuel lines, start with this one:
New fuel hose busted-fire narrowly averted

Safety first!

Good luck,
GK

[Dooodahman]

Thanks for the help guys. I definitely want ot get this solved ASAP. What type/size fuel line do I replace the frunk lines with?

[Smoove1010]

I couldn't find metric sizes locally, but using a combination of SAE sizes (3/8, 5/16, 7/16) I was able to replace the 4" piece and the evap-system pieces in the frunk. My replacements aren't fabric-covered, but concours-correct isn't important to me.

You'll need to do a little searching of the Pelican catalog on this - all the stuff is there, just a little tricky to find.

Good luck,
GK

[Peter Zimmermann]

If you have the 8th Edition of my book, The Used 911 Story (available from Amazon.com), I discuss, briefly, fuel line issues on pages 101 and 102. I would be very surprised to learn that your fuel smell is coming from somewhere other than the engine compartment. As others have posted, DO NOT drive the car until the problem is resolved.

[BE911SC]

^^^ A must-read book! ^^^

[zippy_gg]

First thing first: if you smell gas DO NOT drive the car.
Then start troubleshooting in the "frunk". Raise the car on jack stands and crawl underneath the tank and inspect the lines. If they are anything like the ones on my 86 Carrera they will need to be replaced. You can buy hose by the foot and get new collars and replace yourself.

Then move to the engine bay.
Some of the lines don't look too bad at first


Until you take a closer look at that "J" hose

[Dooodahman]

Peter, I have your book and will reread those pages tonight.

I just went out to the car and to be honest I am not sure if it actually is raw fuel or if it is exhaust. Embarrassingly enough, I'm honestly not sure if I can really tell the difference.

I felt the front lines from the fuel tank along the drivers side of the frunk and they felt dry as a bone. I will check under the tank and in the engine compartment this evening (with fire extinguisher nearby).

[Peter Zimmermann]

The engine compartment lines can "sweat" fuel vapors during cool-down after the car has reached temperature. I remember the first time my shop discovered the problem was after a customer reported that he arrived home from work and parked his car in the garage. Turns out that his bedroom was directly over his garage, and he could smell gasoline when he went into the bedroom an hour or so after getting home.

Regarding exhaust, does the car have all of its original equipment? Muffler? Catalytic converter? Did it pass a change-of-ownership smog test? If yes to all, it's doubtful that your smell is exhaust. It could be, but that's highly unlikely.

[Dooodahman]

Peter, it looks very stock to me, other than a K&N - and my mechanic confirmed this. But, again, I am a novice, so I will post a picture of the engine compartment.

I can't thank you all enough.

[Dooodahman]

Does the hole in the second picture look right?

[kidrock]

that hole in the 2nd picture will not create the fuel smell that you're concerned about, that is a heater manifold and provides warm air.

Did I miss something, or has anybody suggested replacement of the charcoal cannister? This is usually the culprit for fuel smell. But it certainly doesn't hurt to check the fuel supply lines, particularly the pesky one that supplies the fuel rails.

[zippy_gg]

That is just where the white plastic clip goes.
The black "tube" is for the heater.
See if you can put the clip back in; you may have to replace if broken, as old plastic does when it gets brittle with age. Otherwise just put black tape et voila!

[SilberUrS6]

Originally Posted by BE911SC

^^^ A must-read book! ^^^

Absolutely. Peter's book was instrumental in my pre-purchase evaluation.

[Dooodahman]

I just went back out for a good whiff test. I opened the gas cap cover....no smell. Opened the frunk, quickly ripped off the carpets and sniffed around the expansion tank....no smell. Then i sniffed around the engine compartment.....and the smell appears to be concentrated around here:




Is this bad news?

[E Sully]

BoxsterGT, Len, makes up very nice replacement lines. It is not an easy job to get to some of them though.

Originally Posted by BoxsterGT

Here are a set of hoses for a 3.2 911C I made up recently.................



These are the usual 3.2 engine hoses along with sets of front & rear chassis hoses, all done in Metric Braided Stainless Steel. They are made to mate with the Polyamid tunnel lines shown above.

A note about my braided fuel hoses; they use the same rubber compound and have the same lifetime as the plain rubber multi-fuel hose. The only benefit is a bit of abrasion resistance and bling.

Please NO PM's. For answers to your questions, Email me and I will reply with Photos & price details.

Len

[Peter Zimmermann]

Originally Posted by Dooodahman

I just went back out for a good whiff test. I opened the gas cap cover....no smell. Opened the frunk, quickly ripped off the carpets and sniffed around the expansion tank....no smell. Then i sniffed around the engine compartment.....and the smell appears to be concentrated around here:


Is this bad news?

The smell could possibly be coming from the fuel line under and forward of the intake manifold. If you have a good quality mirror, look, using a flashlight, at that area.

[McLaren-TAG]

Semi hijack question here since I've spent a lot of time chasing fuel smells in my car over the last year. Mine are definitely not in the back and I got rid of them mostly by replacing front hoses.

My question is, should there be negative pressure in the gas tank? In other words when I open up the gas cap should I hear the sucking in of air? I'm afraid there is a breather somewhere that isn't breathing.

[Dooodahman]

I looked and saw what looks to be some kind of accumulation in the depression behind and beneath the fuel line you indicated. I'm not sure if it is oil or fuel or maybe just gunk, but there is definitely a stain as shown in the following picture: