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Posted by: mmascari Apr 21 2023, 10:12 AM

I have a 914 with a 3.0l six and PMO carbs. The gas smell is unbearable, especially when the car is in the garage. My wife is about to lose her mind. What do you carb guys do to limit this? Would running the engine with the fuel pump off, IE running out of fuel help with this situation?

Posted by: Osnabruck914 Apr 21 2023, 10:22 AM

If everything was correct, you should not be smelling gas. Find the leak and fix it.

Osnabruck914

Posted by: ClayPerrine Apr 21 2023, 10:24 AM

Most of the carbed 914s have the charcoal canister system bypassed. Make sure it is hooked up and working.

Posted by: GregAmy Apr 21 2023, 10:25 AM

That's not totally true; the float bowl is vented to the atmosphere. But the smell should certainly not be "unbearable".

Are you sure you don't have any leaks somewhere else? The fuel system should theoretically remain pressurized at your set point, 3-4 psi or whatever (though some fuel pumps will back-leak that pressure slowly).

Another common place for leaks - what made my D-Jet car "unbearable" in my garage - was rust holes in the tank sides where the wear carpet/felt retained moisture. I finally figured it out when fuel started seeping on my shoe soles, with a small puddle on the garage floor, any time the tank was over about 2/3-3/4 full. - GA

Posted by: ClayPerrine Apr 21 2023, 10:35 AM

On a stock 914-6 the float bowl is vented into the air filter assembly. That is supposed to be part of the charcoal canister system, and will pull the fuel vapor into the carbs instead of venting it to the atmosphere.

This, however, does not apply to K&N water shield air filters. And I do agree, the small venting from the float bowls should not be unbearable.


And I agree with the tank rust issue. It started happening to Betty's 914 on the way home from Okteenerfest one year. Drove me absolutely bonkers trying to find the fuel leak. Ended up buying a new tank to fix it.

Posted by: mmascari Apr 21 2023, 10:37 AM

Thanks for the replies. I will look for leaks.

Posted by: JmuRiz Apr 21 2023, 10:42 AM

Let us know what you find, I've always found carb'd cars to smell of gas too. Mine is mostly burnt-off gas stink from driving into the garage.

My old 2.0/4 with carbs and my 356 both. The 356 you can turn the petcock off to drain the bowls...but you still have the smell of the car running until it runs out.

Posted by: dr914@autoatlanta.com Apr 21 2023, 10:45 AM

something is leaking somewhere, maybe use a sniffer and see where

Posted by: NARP74 Apr 21 2023, 11:15 AM

This also brings up the return line vs no return line debate. That pressure has to go somewhere...

Posted by: ClayPerrine Apr 21 2023, 11:22 AM

The factory pump for an original 914-6 looks like the one for the 914 with fuel injection, but it delivers a much lower pressure. The factory six had a return line that only came from the pump.

Posted by: rfinegan Apr 21 2023, 11:24 AM

I had gas smell in may garage too, on a Carbed 75 914-4. I restored/ refilled the charcoal canister and the smells are controlled MUCH better. Check your gas cap for gaskets/seals too. Lots of smells and vapors in this area too
I found the gas tank produced most of the smells VS the carbs.
I hope this helps narrow your search

Is the smell stronger with a Full tank or less smell near empty?

Posted by: Root_Werks Apr 21 2023, 11:50 AM

Don't forget carbs vent to the atmosphere, there will probably always be a little fuel smell. Best systems I've seen are factory aircleaner assemblies. Having simple K&N style filters on a six means you'll always sniff a little fuel.

As others have said, if it's that bad, you probably have a leak someplace. Probably something that is just enough to seep a little. I swear, one drop of fuel will stink up a 1,000SQFT!

Posted by: r_towle Apr 21 2023, 12:36 PM

Todays fuel sadly evaporates much faster with the Ethanol component.

If storing a car, I would suggest adding a fuel shut off valve which you shut off once the car is park, yet still idling.
This will suck the remaining fuel out of the carbs.
Starting requires a bit longer, but you will take the smell away in storage.

Rich

Posted by: mlindner Apr 21 2023, 12:53 PM

I would check all hose clamps to lines, filter, pump. My new pump and filter came together with hose and clamps....the provided clamps leaked badly. Its been two years now and no gas smells. PMO's, single fuel line, low pressure fuel pump, inline fuse.

Posted by: BillJ Apr 21 2023, 12:55 PM

Gas cap as well. If that seal is not working right can definitely leak fumes. I had this issue once. New gas cap fixed it

Posted by: r_towle Apr 21 2023, 01:01 PM

Fun fact.
The evaporation "system" on a stock 914 expansion tank (the tank at the filler location) is just a hose the routes down behind the tank and out onto the ground....into the atmosphere.

Its a vapor leak that can/will smell up a garage.

rich

Posted by: emerygt350 Apr 21 2023, 01:06 PM

Yeah, look around. I just pulled mine out to do some seat of the pants tuning and was thinking to myself I was running really rich. Popped the hood to check my mps and fuel pressure and low and behold, the injector rail on the passenger side was weeping. I cried a little too.

(Poorly installed clamps by the current owner)

Posted by: r_towle Apr 21 2023, 01:08 PM

be happy you found it this way versus a fire.

Posted by: 930cabman Apr 21 2023, 01:20 PM

Better get things fixed quick, or you may find yourself and your stuff at the curb.

I have had carb'd cars for years and never had the gas smell

Posted by: nditiz1 Apr 21 2023, 03:27 PM

As stated carbs vent to the atmos,

I have PMO's on my 6 conversion - no char canister, vent goes from tank to engine compartment

I also have PMO's on my 911SC. This one smells even worse as it likes to run rich. Sometimes the fuel smell will seep into the main garage and my wife hates it. No leaks on either of my cars. Best thing I do is leave the door open a little after I pull it back in.

Agree with running the bowls empty if you really cant bear it.

Posted by: mmascari Apr 21 2023, 05:37 PM

I am going to bring the wife out to the garage later and have her sniff around the car and tell me where the problem is. My nose doesnt work very good. LOL

Posted by: 914_teener Apr 21 2023, 05:48 PM

Hunh?


http://www.914world.com/bbs2/index.php?showtopic=108524

Posted by: porschetub Apr 21 2023, 11:19 PM

Not sure about that,with the LP pump not running there is no residual pressure like an FI car,the fuel bowls are full and stay that way until the engine is running again then the float valves regulate fuel demand from there as set by the float levels .
The OP may have too higher float setting or bad float valves or as mentioned an external leak .
All factors to consider.

Posted by: 930cabman Apr 22 2023, 07:23 AM

I have ran carb'd Porsches and VW's for years always dead headed (no return line) and never had an issue

Posted by: porschetub Apr 22 2023, 01:17 PM

done the same for years ,my six engine is no differant .

Posted by: mmascari Apr 22 2023, 06:08 PM

Looks like the leak is in the front of the car. I had a carpet my car was parked on and it was soaked in fuel. Tomorrow I am going to climb underneath and see. I relocated the fuel pump up front so there are a few hoses / connections.

Posted by: porschetub Apr 23 2023, 03:41 PM

Well done good on you ,hopefully not a rotten tank or pump leaking,a leaking connection will be easier to deal with,did you have any drips with the pump primed ?.

Posted by: mmascari Apr 23 2023, 03:47 PM

I had to pull the tank of course. The return fitting was loose. Anyway, I decided to get rid of the return line from the Fuel pressure regulator. Is it true that we can remove this line if we have carbs? I want to make sure.

Posted by: rfinegan Apr 23 2023, 04:01 PM

pros and cons ...but sure you can remove the return line on carbs, depending on the pump and regular you have.

Posted by: porschetub Apr 23 2023, 06:10 PM

Good find,the washers are a bit funny on these ,metal ones can leak IMO the fibre washers are the way to go and worked for me on the feed side,I used the return line as a conduit for the power supply wire to my pump and earthed by linking to my crossmember to my pump.
I don't have a return for the above reason and if you have good float valves and the right fuel pressure/ pump you will be good ,strange how some folks run LP pumps that make a lot more pressure than needed even via a regulator,my CB/carter pump only required fine tuning using my Holley regulator and I ended up with 3.3 psi with my Zeniths but understand the Webers run a little higher which think the PMO's are based on.
You will be fine ,cheers.

Posted by: mmascari Apr 23 2023, 07:46 PM

Thanks, I am using a low pressure Pieburg fuel pump mounted in the front and have a PMO fuel pressure gauge in the engine compartment that feeds each bank of carbs. Pressure is showing right where I want it without the return line.

Posted by: porschetub Apr 23 2023, 08:17 PM

You will be good then,cheers.

Posted by: targa72e Apr 23 2023, 10:07 PM

Glad you found your problem was just a leak up front. That said Carbs stink. I have a -6 conversion and have had multiple engines and carbs (Webers, Zenith, PMO) and they all smell. There is a lot of gas in the float bowls. If you park a your car fresh from a drive in the garage the heat from the engine will cause the fuel in the float bowls to percolate and evaporate stinking up the garage. I now park mine in the driveway after a drive and then pull in once its cooled down.

john

Posted by: mmascari Apr 24 2023, 10:31 AM

Good idea, thanks John!

Posted by: Justinp71 Apr 24 2023, 10:37 AM

Yes, I just leave the garage door and side door open for about 45 minutes after a drive seems to do the trick. Also I took the outlet of the engine breather and directed it to the side of the carb rain hats (there is a fitting in the rain hat), this helped cut down overall smell too (recirculates engine breather air to the intake).

Posted by: Rufus Jan 22 2024, 05:15 PM

Resurrecting an older thread to add info.

This $135 Rigid sniffer allowed me to quickly locate the gasoline vapor leak PO’s two “experienced professionals” were unable to find on 9140431482. The greatest source was a SS braid hose; possibly due to internal rubber hose incompatibility with E85 gas?? Or maybe shift mechanism chafing the SS braid??? Just guesses. The SS hose routed thru the cabin tunnel. The leak found worst near the shifter.

And BTW: the “rubber patch” solution reported by PO in 2013 as a fix, failed the sniff test by women in my household.


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Posted by: r_towle Jan 22 2024, 05:20 PM

Porsche 356 has carbs and a fuel shutoff underneath the dash.
With today’s fuel, I find it best with any carbed engine to turn off the fuel supply while the engine is running and let it suck the carbs dry.

Also, when going to a car show, simply putting tennis balls into the intake stacks helps a TON to keep the hot fuel from evaporating and smelling things up.

Today’s gas has a lot of ethanol. That evaporates really fast.

Rich

Posted by: Rufus Jan 22 2024, 05:23 PM

100% Agree! In addition to an ignition shut-off, I added a FP cutoff for limiting fuel level in the carb floats before parking in the garage. I also use E0 gas exclusively

Posted by: JmuRiz Jan 22 2024, 08:48 PM

Lucky duck

Yes the petcock on the 356 is nice. Even with that the e10 here (even with marine stabilizer) it caused the PO’s tank lining of the original tank to fail and clog up my freshly cleaned and redone from petcock downstream refresh last month.

Posted by: 73-914 Jan 22 2024, 08:50 PM

This is why I use alcohol-free gas

Posted by: ClayPerrine Jan 23 2024, 03:09 PM

There is a fairly new station near me that sells ethanol free gas. We make sure to fuel the factory six there and nowhere else unless forced to.

But it is only 90 octane, so we have to put in octane boost with each tank. But it is worth it.

Posted by: Jamie Jan 23 2024, 03:29 PM

I've been running my 914 on locally available 90 octane no ethanol fuel for some time, but wondering about using it in my new Cayman 718 turbo? How about alternating fill-ups to keep the octane up?

Posted by: flipb Jan 24 2024, 11:11 AM

I'm not sure what the advantage would be of putting ethanol-free fuel in a modern car. They're designed for the blended fuels. And being fuel injected, evaporation isn't a concern.

Posted by: brant Jan 24 2024, 01:23 PM

Unless storage or length of time is factored in
Pump gas with ethanol has less than a month of shelf life
I heard somewhere it may be under 3 weeks

Ethanol can still gum up injectors
So the frequenc of fresh fuel (how many weeks the car is not driven) can definitely factor in

Posted by: mmascari Jan 24 2024, 02:50 PM

By the way, for anyone that cares, the smell of gas was from an actual leak under the tank. It leaked on to a carpet that I had under the car. The carpet was saturated. Luckily no fire. As soon as the leak was fixed I no longer have any gas smell

Posted by: Rufus Jan 24 2024, 02:57 PM

“I'm not sure what the advantage would be of putting ethanol-free fuel in a modern car.”

Slightly better mpg due to slightly higher energy content. Whether worth the price difference is questionable depending on how great the difference is.

Posted by: GregAmy Jan 24 2024, 03:32 PM

Prooooobably won't make any difference on our fuel economy without wideband feedback?

In a modern car with AFR feedback, the ECU will detect a lean condition due to the presence of ethanol and inject more fuel; our stock D- or L-Jet fuel system is injecting the same mass of fuel regardless what we put in the tank.

I can't offer if "energy content" would be significant, given I don't think any of us are sensitive enough to notice it and make any change in how we drive the car.

For us, ethanol-free would actually slightly reduce emissions (if driven the same) but at the expense of the issues with ethanol being in our older fuel systems.

Posted by: Rufus Jan 24 2024, 04:07 PM

My quick search said the difference is slight, but “measurable”. Don’t know if in a lab, on a dyno, or by a consumer.

And more food for thought: Lambda=1.0, stoichometric, is A/F=14.7 for E0; 14.0-14.1 for E10, and 9.8 for E85. The greater the ethanol content, the greater ratio of fuel to air for Lambda = 1.0 which the narrow band O2 sensor seeks to run at.

Posted by: Rufus Jan 24 2024, 04:31 PM

I pretty much agree.

The specific gravity of E85 is .79 vs .72 - .77 for pump gas.

I’m no carb tuning expert. But if E85 has a slightly higher density than pump gas, and I’m thinking right, the A/F ratio with E85 would be slightly higher (leaner) than with E0 at the same carb calibration.

As far as FI with closed loop A/F control using a narrow band O2 goes, the A/F will operate at stoicometric (Lambda = 1.0; the ratio where 100% of both air and fuel are consumed during combustion) for a variety of gas / ethanol blends as long as the fuel system has sufficient authority (range of control adjustment) to meet ECU demand.

Posted by: Rufus Jan 29 2024, 08:55 PM

A couple more thoughts to share on venting a 914’s gas tank for use with carbs and without the evaporative emissions control system …

This’s my plan. When I get my /6 up and running, I’ll report back. I hate the smell of gas in the garage.

Below is a photo of what I ran on my ‘67 Vette for years. Tank venting was never a problem, and in the 5 years it was in the garage under bedrooms there was no gas smell. Note the approximate size of the vent hole; 1.5-2mm at most?

A 914’s difference is the tank is under the frunk lid, where there are pathways to the cabin at floor level. Also consider that gas vapors are heavier than air, and sink to the floor.

So I’m stuffing the cut off and deburred big threaded end of a ball (basketball, football, volleyball) inflator inside the vent hose. Will locate it at or before the uppermost point as vapors leave the tank / expansion tank and then travel downwards to where they exit under the car. Hopefully this will lessen vapor escaping thru the vent tube.

And this’s how VW configured the tank vent hose in Bugs of the ‘60’s (pic from The Samba), before evaporative control systems. By using the difference in density of air & fuel vapors as a natural check valve kinda like a kitchen sink drain trap in reverse


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Posted by: r_towle Jan 30 2024, 09:22 PM

Yah, this might have been a different thread if you started with that.

Lol