Gas fumes, have you ever smelled them?

[JimLev]

I have a very slight smell of gas fumes from my hotrod. I’ve checked every inch of line, the regulator, injectors, pump, and filters, etc, they are all bone dry. I’ve never filled the tank more than 3/4 full.
I have the charcoal canister (FFR supplied parts) plumbed into the purge valve on the intake and all is bone dry there too.
What I can’t get an eyeball on until I remove the roof and waterfall. Is it possible the fumes are coming from the roll over valve? Doesn’t it stay open unless the car tips over?

[Just 1 More]

I have one of these I bought when building my Camaro and didn't use it. I'm going to add it to the '33 on the check valve. The idea is to mount this thing up high and drop a hose off the other port with a
sintered bronze filter on the end.
https://www.rockauto.com/en/moreinfo...971360&jsn=715
https://www.napaonline.com/en/p/NOE7...&gclsrc=aw.ds&
vapor canister by F G, on Flickr

[JimLev]

Is that some sort of charcoal filter?

[rthomas98]

Question what did you use for fuel line? I had to replace mine because it was sweating fuel ever so slightly. You won't see a leak but you will smell the vapor for sure. The issue is some of the lines you get are not rated for ethanol and after this last year they upped the amount that is in fuel now. Pick up one of these

https://www.amazon.com/Detector-Port...gion_id=972485

Save yourself some headache by pinpointing it. I have feeling your experiencing the same thing I did on my roadster.

[Mastertech5]

Is the purge valve being controlled by the computer? I assume it is. I wanted to use the FFR canister because it was smaller and easier to mount but I think the ports weren't configured for use with the GM computer. I'd have to look again. There have been many complaints about gas smell by many builders of all FFR cars. Most of those were on older versions that didn't come with canisters and they made their own. Did you use the gasket FFR supplied for the sending unit in the tank. I've seen on a few that it will leak. Someone used and suggested a Ford gasket for an appropriate Mustang, but someone else said that is what FFR sends in the kit so???? On newer OEM vehicles starting a while ago there is also a vent valve on the fresh air port on the canister that the computer will close to perform diagnostics on that system. Mine doesn't have that but I put the OEM filter on that port to keep most dirt out of the cannister. AC Delco pn 215-686. The nipple on it uses a 5/8 hose which matches my cannister. Available from Amazon.
The fresh air port on the canister should be toward the top on how ever you mount it, upright or sideways. I used Breeze Automotive's larger vent kit. It has a metal ball in it instead of what FFR sends. Is it possible the ball is getting sucked up and closing the valve when the purge valve opens causing the canister to not be evacuated of fuel vapor. Just some thoughts that may help. Edited it 4 times.

[JimLev]

Rthomas, thanks, I just bought that sniffer. The fuel line is what FFR supplied. I did buy line from NAPA and Gates for the charcoal canister, both rated for fuel. I’ll sniff the lines when it arrives.

Bruce, I used the FFR canister, it’s mounted below the tank, that’s about the only place it will fit. I used the FFR gasket on the sending unit and put a skim coating of fuel resistance sealer on it, it’s not leaking.
I don’t have anything connected to 2 ports on the top of the canister, I’ll check out the p/n you said.
The ECU doesn’t have an output to control the purge valve that is on the engine. I have it wired to a rocker switch in the console. Maybe I need to use it more often.

[Just 1 More]

Is that some sort of charcoal filter?

Some kind of emissions filter thingy. I don't remember how I found it but it says "Quality-designed to properly control the loss of evaporative emissions from fuel systems to the environment" It's for a Mazda and listed as a Vapor canister.

[narly1]

I'm not sure if these links are applicable to the usage case where there's a purge valve located near the engine but sharing anyways.

https://www.tanksinc.com/index.cfm/p...rod/prd811.htm

https://www.tanksinc.com/pdf/in-line_vent_valve.pdf

The literature would seem to infer that a charcoal filter is not necessary if you run a check valve.

When I get to this stage in my build I think I'll be installing both to keep the stink to a minimum.

Earl

[JimLev]

Good info guys.
The sniffer will be here on Sunday.
I’ll pull the canister today and see if it or the line to it from the tank has fuel in it.

[Mastertech5]

It will be heavy if it has fuel in it. You should turn on the purge whenever you go say , over 45mph constantly for a while. That's how OEM ones work. It won't affect your driveability that way or load the engine rich at lower RPM. I looked up that canister online and it is for many older Fords. The 2 big ports are for fresh air and there are dust caps for them.
PN D1AZ-9E602-A. Many guys on Ford forums grab them off of cars at a salvage yard. I pulled the FFR canister out to look at the ports and it looks like it should only be mounted one way by the way the mounting tabs are situated. I couldn't find a diagram on hose routing. I assume the small port goes to the purge valve and the other to the tank. Post your fix , I'm super curious.

[JimLev]

As usual other things came up today but tomorrow looks good for pulling the canister.
I have the small line to the purge valve and the other line to the tank.
The two big ports are at the top and have a filter of sorts in them. I’ll post what I find.
In the past when I did turn on the purge switch at idle the RPM dropped and then recovered.
If I turn it on at say 45 MPH how long would it stay on if it was controlled by the ECU.

[Mastertech5]

Not sure. I never monitored it for any length of time with a scan tool. I don't have one myself. Could be all the time. You should get a switch that lights when it's on so you don't forget it's on. I'll look into it and get back to you if I find anything. No access to service manuals anymore, unless I purchase one.

[Mastertech5]

The computer pulse width modulates the purge solenoid to varying percentages of opening determined by data of other sensors. Mostly it opens at coast at higher speeds. Don't you have a GM compuer? I thought you did. It should be able to control it, being an LS3. Was there a plug for it in the harness. Mine will throw a ck engine light if not connected, it says in the instructions, but it is an emission compliant package. LS computers and harnesses are available from Chevrolet Performance Parts although not cheap. Part # for an automatic is 19354347. Harness part# is 19369375. These are for emissions so you'd need all the emission control stuff. Probably not what you want. A few grand more because of CATS.

[JimLev]

I’ll check the wiring again from the GM ECU. I don’t believe there was a connector for the engine mounted purge valve. I bought a connector and hooked it to a lighted rocker switch in the console.
Here is the charcoal canister. I can’t find any info on the -AA canister, there is info on line for the -AB canister from a 94-95 Mustang.
There is no connection to the large ports on the top. They do smell like fuel as they probably should.
D333C91F-2579-49D3-B483-F924ADC8E678.jpg

0C16D3D2-CABA-4C76-B26C-6C0F03E80F31.jpg

Looking at this -AB canister on line I see the 2 large ports and Tee’d together with a hose that probably brings in fresh air from a different location.
0AACDD75-9705-4D00-9A26-F65BD822F8A2.jpg

[Mastertech5]

It looks just like mine. The different suffixes are just for slightly different models. I believe it should be mounted horizontally with the short dimension vertical. My purge connector is on the passenger side of the harness along with the MAP/BARO sensor connector.
IMG_20230211_124351_hdr.jpg
The one that is wrapped around the overflow tank.

[JimLev]

I’ve checked my wiring and the prints, no CPS connector. Do you know what connector and pins at the ECU end it is hooked to?
Maybe me not having that connector has something to do with your engine having CAT’s and I don’t?

I connected my vac pump to the line that goes to the intake, as soon as I turned it on the back yard reeks of gas so I need to run the purge valve a lot more, tee the fresh air ports together like in the Mustang pic.

I have my tank mounted with the fresh air ports on the top, you think I need to mount it sideways?
Would the 2 small ports be at the top or the bottom?
My manual doesn’t address the canister.

AEC973EE-3643-41A9-AE3B-75ECF601817D.jpeg

CD0E8A30-E0E0-4317-B90E-2DB078371F79.jpeg

[Mastertech5]

FFR doesn't mention the canister installation at all, just here you go, figure it out. I just looked at my instructions for my canister and they have pictures of how you can mount it. The ports are configured differently. It does show one mounted vertically, ports on top, so I guess that's ok. What I said was because I don't ever remember seeing one mounted that way on a vehicle. Usually they are bolted to a bracket that is bolted to a flat horizontal area in the rear. I guess your good. The idea is to not let the vacuum line be at/near the bottom, as mounted, to prevent liquid fuel from being sucked up, so they should be at the top. If they sent you a purge valve with your engine it doesn't make sense there wouldn't be a connector in the harness for it. Our ECMs may be the same one but be programmed differently for each application. Connect and Cruise all included, correct? I got 30 pages of instructions with my engine. Trans was separate.

[JimLev]

Yes Connect and Cruise, the purge valve was mounted on the engine when I got it.
I guess I may have to hit the junkyard to find those 2 caps that fit on the fresh air ports if I want to connect a hose like in the Mustang canister pic.
After having the vacuum pump suck on the canister for an hour all of the gas smell is gone.
I may have to use a PWM controller to operate the valve or maybe put a small oriface in the tube and have the valve open while the engine is running.
Thanks for the help.

[Mastertech5]

Sure. Glad to help. Those caps go directly on the canister from the pictures I saw. Mustangs may have a different setup.

[Dave 53]

Horrible gas smell on my 818. Ended up the hose clamp attaching the filler neck to the gas cap hardware was tight, but not tight enough.

I don't have a charcoal canister. My tank vent terminates in an old water bottle to keep any gas from dripping at the race track. No smell noted.

[JimLev]

Got the gas sniffer yesterday that rthomas recommended (post 4 above), it’s very sensitive. No vapors leaking thru the fuel lines. It was all from the charcoal canister fresh air vents due to the canister being saturated with gas vapors.
Yesterday I bought Dorman 47032 PCV elbows from AutoZone, machined off the barb on one end so it would fit into the canister. I’m adding 2 long hoses so fresh air can be pulled in from the rear of the car.
If I ran the purge valve more I wouldn’t have had this problem.

1AC5B7E9-2C33-4E56-BEB7-DF0B5CDAFB14.jpeg

Found this on the internet for a GM purge valve operation.

The PCM energizes the canister purge solenoid and allows vacuum to purge vapors from the canister under these conditions:
150 seconds have elapsed since the PCM entered closed loop.
Coolant temperature is above 176 degrees F. (80 degrees C.).
When the PCM is not enabling injector shut-off, such as on vehicles with traction control while one drive wheel is spinning.
The idle contact switch in the IAC motor is open.
Vehicle speed is above 20 mph.
Engine speed is above 1,100 rpm.
The engine metal temperature sensor is not indicating excessive temperature.
Low coolant level is not indicated.

If any of these conditions are not present, the PCM does not energize the canister purge solenoid, and the gasoline vapors from the fuel tank are stored in the canister.
When the engine is running, intake manifold vacuum is supplied to the TPCV valve. This vacuum opens the valve and allows vapors to flow through the valve into the canister. When the engine is not running, the TPCV valve closes, and fuel vapors are contained in the fuel tank. If the tank pressure exceeds 15 inches of water with the engine not running, this pressure forces the TPCV valve open and allows vapor flow to the canister. The canister contains a liquid fuel trap that collects any liquid fuel entering the canister. Condensed fuel vapor forms liquid fuel. This liquid is returned from the canister to the tank when a vacuum is present in the tank. This liquid fuel trap prevents liquid fuel from contaminating the charcoal in the canister. The EVAP system reduces the escape of HC evaporative emissions from the gasoline tank to the atmosphere.