Smell like gas after driving car (real bad)

Discussion in 'Classic Mustang Specific Tech' started by streetstang67, Nov 24, 2009.


  1. streetstang67

    streetstang67 Member

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    I've had this car finished for several years, and I've put up with the gas smell every time I drive it, but its just getting old. The exhaust is terrible, it smells like a leaf blower; and I smell like gas after I drive it. I'm guessing maybe it's running too rich, maybe the timing is off, maybe the carb is all wrong, I don't know; any suggestions? This can't be too hard... Thanks

    Its a '67 mustang, 289
    Holley 600cfm vacuum secondary carb
    Edelbrock Performer intake w/1" open spacer
    Comp XE256H Cam (lift: .477,.484, duration: 256, 268)
    Multi-angle port/polish job on factory '67 heads
    Stock valves (1.77, 1.45) with springs to match cam.
    Comp magnum roller tip rockers (1.6:1)
    Hooker comp headers (long tubes)
    H-pipe w/dual Flowmasters
    #1
  2. rebel65

    rebel65 Member

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    buy some cats
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  3. JonK

    JonK Member

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    That's helpful:nonono:

    I think it's time for a tune up, look up your carb. model number, holley has tuning instructions on their website, you can get it close (closer than it is now I'm sure). Make one adjustment at a time and test, always remember your starting point (turns in/out). A hand held vacuum gauge will help, should tell you if you have a leak and what reading you get tells you early/late timing, etc. Get a timing light, they're not expensive (sears, etc.) and you will probably use it again or pick one up on CL just make sure it works. Look up directions for use, you have to disconnect/plug the dist/carb. vac. adv. line to get a proper reading. They are simple to use. I found out my timing chain was stretched when I used mine due to varying timing.

    Check all your fuel line hoses and the seal at the gas cap, see if it's shot, it's spring loaded and the tank vents through it. Check all your vacuum lines and replace if you see ANY cracking when bent. Check your vac. adv. on your dist.- remove the cap, find the arm that extends from the back of the adv., pull the vac hose from the carb - suck on the hose hard as you can= you should see the arm pull into the adv. if you don't the adv. diaphragm is bad- replace. If the adv. is bad your timing isn't adjusting with RPM's and you have a vacuum leak to boot = bad running, bad mpg.

    Clean the carb. with carb spray, you may have bad gaskets/base gasket, run some 'seafoam' in the carb. and tank, read the bottle as through the carb will clean out the carbon but produce a ton of white smoke, do it away from houses, etc.

    Try some fresh plugs, make sure you have the right heat range plugs, look them up. That should be a start.
    Jon
    #3
  4. rebel65

    rebel65 Member

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    it is helpful, cars without cats smell like gas... maybe not to the extent his does but a lot of people complain about it.
    #4
  5. 2+2GT

    2+2GT Well-Known Member

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    You have two problems.

    1) Your car stinks.

    2) The stink is getting into the car.

    I got a real good deal on my 66 FB. It stunk of gas inside. I figured out the rust on the top of the gas tank was allowing fumes in the car. New tank, no smell.

    If it's not that, then it's exhaust, and you need to follow the suggestions above.

    HOWEVER. Even if pure skunk-stink was coming out of the exhaust, it should not be getting into the car. You need to start looking for missing rubber plugs, bad sealant around the gas tank, bad decklid gasket, bad taillight gaskets, loose wiring plugs, rust holes, etc. If the car is tuned to the max, and you get nice clean exhaust in, guess what? It's still toxic, and will kill you, so start looking at the seals.
    #5
  6. hungrymonkey

    hungrymonkey White by Birth, Trash By Choice Founding Member

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    I had a fuel pump go bad on me, It made my truck smell like gas. Turned out that it was dumping most of the fuel into the oil.
    #6
  7. 795.0

    795.0 New Member

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    My car was the same way while idling in my garage, it would even get into my clothes. I got a wideband oxygen (O2) sensor and dialed in my idle to around 14.2 and the smell has completely gone.
    Here's a good link for the Holley carb:
    YouTube - Holley Carbs - Setting Idle Mixtures
    My next question is do you have any steel braided fuel hoses? I've heard some brands of that can give off gas fumes with todays fuel also.
    #7
  8. streetstang67

    streetstang67 Member

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    I've spent most of the afternoon working on this...

    First, I adjusted the valves, I'm now getting a little bit of a chatter, but overall it seems okay. Next, I looked over the carb and looked for vacuum leaks, everything was good to go. Then, I got a timing light and checked the timing. It was set pretty high (16?), so I dropped it down to around 12*. Finally, I adjusted the idle mixture screws on the carb to get max vacuum. I've got electronic ignition, so no need to mess with vacuum advance, etc.

    Overall, I think backing the timing off did help a little, but its hard to tell without driving it for a while. The carb seems pretty clean, so I don't think any cleaner is needed. Fuel tank is new, so no rust problem there.

    Now that I'm running out of options, I'm guessing the carb or jets are too big for my setup, so maybe I need to jet it down a couple sizes. The other thing is that I could be getting exhaust fumes in the car from the trunk seal and door seals, all of which are new but may not be sealing off.

    Thanks for the feedback so far...any thoughts now?
    #8
  9. tx65coupe

    tx65coupe Active Member

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    My 65 does this sometimes. It doesn't seem to be running really rich though. There is no black smoke when I step on the gas or rev the engine.

    When it still had the 200 I6 in it, I don't think it was as bad as it is now.

    I'm thinking that maybe there is an exhaust leak in the intermediate pipes or H pipe somewhere. When we first got the car back on the road last spring, it wasn't that noticable, but it seems worse now. I don't hear an exhaust leak though.

    What does 14.2 mean?
    #9
  10. tx65coupe

    tx65coupe Active Member

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    All the weatherstiping and seals have been replaced on my car as well. These cars never sealed up real tight even when new though.
    #10
  11. RGS0907

    RGS0907 New Member

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    If it's a raw gas smell as well, you could check to see if the fuel sending unit is leaking. The aftermarket ones can be real garbage.
    #11
  12. Bullitt

    Bullitt Packin' Heat Founding Member

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    I recall a post at one point where a similar complaint was made and the poster ended up replacing the rubber line between the filler neck and the tank. Evidently it was seeping gas through, not enough to see, but you could certainly smell it.

    I've got a problem in my car as well, although not to the extent you're describing. Changing to EFI helped a lot! Make sure all your exhaust gaskets (manifold to head, manifold to pipes, etc) are all sealing well. An exhaust leak can give you a tick that sounds like loose rockers.
    #12
  13. tx65coupe

    tx65coupe Active Member

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    The smell from mine is exhaust smell not raw gas. But I don't hear an exhaust leak. I am going to look tonight for evidence of a leak.

    Good point about the filler neck joint. That is prone to leaking. I have seen some that were really bad. I have not seen one that didn't leak a little. I have all new parts on mine and the trunk usually smells a little like gas.
    #13
  14. woodsnake

    woodsnake Active Member

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    Does it smell of gas all the time, or when idling? I see you have cam in car, valve overlap can cause stinky idle...
    #14
  15. streetstang67

    streetstang67 Member

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    Mine smells all the time, and I do get lots a black condensation from the exhaust...is that a sure sign of running too rich?
    #15
  16. woodsnake

    woodsnake Active Member

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    Too rich, or perhaps improper choke adjustment.
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  17. tx65coupe

    tx65coupe Active Member

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    Mine has not developed the sooty carbon condensation. It just smells like its not completely warmed up. What I mean is how older cars have smelly exhaust when they are first started then it goes away when they are warmed up. It can be hot outside and the car is warmed up and it still smells like that. Does that make any sense at all.

    I wonder if its a choke issue. I have looked at the choke and it is not closed. I wonder if for some reason it is not all the way open when the air cleaner is on.
    #17
  18. 67CoupeDriva

    67CoupeDriva Member

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    Not sure if it was my post, but I had this problem in my '67 coupe and the filler neck rubber was the culprit. Looked OK from the outside, but inside it was cracked and was apparently leaking just enough into the trunk to stink the place up :)
    #18
  19. RGS0907

    RGS0907 New Member

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    There is a vacuum under the rear of the car that develops when you are driving. If you have any leaks in your trunk, around the gas tank, or anywhere else it will pull the exhaust right in through your trunk.
    #19
  20. ahaedike

    ahaedike New Member

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    I had the same problem. This post really helped me find the problem, thanks. My wife was complaining the kids smelled like gas after riding in my '65 Coupe. She said I had a problem with the car. I opened up the trunk and pulled everything out, down to bare metal. Got back in the car and drove like a madman around the neighborhood. Stopped, opened up the trunk and saw a wet spot around a pin-hole in the top left corner of the gas tank. A tiny rust hole in the gas tank splashing gas up into the trunk. Sucks most... the wife was right. Will be replacing the next next weekend.
    #20

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