Gasoline in EVAP Line @ Carb?

[1987 GMC Jimmy]

The title is basically it. I was pulling vacuum lines off my carburetor, and the fattest one that goes to the purge valve for the charcoal canister leaked gasoline out. Now, I flooded the carburetor a couple times while I was having ignition control module problems so I don't know if some could have leaked in there with vacuum happening, but I was also wondering if gas was getting sucked out of the canister and getting past the purge valve. When I put my face by the canister either in the engine bay or in the wheel well, I can smell gas, and it's raw but not overpowering. I have an intermittent backfire out of the tailpipe and a lot of misfiring. It'll idle correctly one minute and start missing really bad until it slowly dies or it'll just abruptly die even when it's running okay. I'm getting ECM codes 13, 44, and 45. They'll come and go with no apparent pattern (not hard codes), but it favors the lean exhaust. Oxygen sensor is new, and I haven't had any problems with it in the past. I don't think it's that because the car would at least run in limp home mode, and it's not even doing that. It actually broke down about 100 feet from my driveway the other day. I was driving with my come and go SES light, the car backfired brownish-blackish smoke, and died about a mile and a half from my house and wouldn't start for a few minutes. The car will always start but dies or starts misfiring shortly thereafter. Anyways, I managed to coast it pretty far, but I live on a hill so I didn't quite make it all the way. I've checked for a burnt exhaust valve and nada. I checked the valve train for any problems in actuation, lash, or pushrod bending and it all looks great. It's still got a tick, though, right at the passenger side bank. Carb is getting good fuel, but I'll check the filter just to be safe. And it's getting good spark. When it runs right, it'll show about 19 in. of Hg on the vacuum gauge, but that'll fall down once it starts to run crappy. It'll just sound like its running on seven cylinders, then six, and so on to where it sounds like a 2 stroke small engine, and I'll shut it off because it won't die sometimes, just keep going EGR valve is also fairly new and no codes for that. 305 has 80,000 miles on it. The only thing I've thought to replace are the intake gaskets. It's too tight to spray a combustible in there, but if anyone has any suggestions, I'll take them and run with them.

 

[Camar068]

did you run through the vacuum chart? I'm sure someone will chime in regarding the gas in vac line to the canister. I googled vacuum reading chart to find the link below. Might want to compare charts just to make sure before you dump time/money just with just that one chart as a reference. Sorry I like to hear/read the same thing from multiple sources prior to me being sure.

http://www.onallcylinders.com/2016/03/31/vac-visual-quick-guide-vacuum-gauge-readings/

 

[1987 GMC Jimmy]

Thanks. I saved it because it's a good picture. Mine doesn't read in those low numbers that I know of. It'll do alright and just die all of a sudden or start missing worse and worse until the idle is comparable to a series of coughs. Here's the emissions routing, too, by the way.

 

[Camar068]

No pro on it, just googling trying to help.

I'd start with starter fluid at all points of vacuum.

2nd I'd check to make sure the o2 sensor wiring is not grounding out.

After googling, I found these for the codes:

http://www.misterfixit.com/code44.htm

http://www.misterfixit.com/code45.htm

Code 13 seems to be strictly o2 sensor related....

" - A failed O2 sensor is the most common cause of a Code 13
- A quick test for the O2 sensor circuit from the ECM would be to unplug the O2 sensor and check voltage from the harness side to ground. With the ignition on and the engine off, the reading should be around .5v."

 

[1987 GMC Jimmy]

No pro on it, just googling trying to help.

I'd start with starter fluid at all points of vacuum.

2nd I'd check to make sure the o2 sensor wiring is not grounding out.

After googling, I found these for the codes:

http://www.misterfixit.com/code44.htm

http://www.misterfixit.com/code45.htm

Code 13 seems to be strictly o2 sensor related....

" - A failed O2 sensor is the most common cause of a Code 13
- A quick test for the O2 sensor circuit from the ECM would be to unplug the O2 sensor and check voltage from the harness side to ground. With the ignition on and the engine off, the reading should be around .5v."

Is it a fixed value of around .5V, or is it like an up and down sine curve type thing?

 

[Camar068]

I read that as testing the ECM side (since your disconnecting the o2 sensor) so I'm guessing a steady 0.5V. Keep in mind that's what I found on the net, so take that for what it's worth.

 

[Camar068]

Any luck with the starter fluid leak detection? Short burst and not near the distributor, or keep a water hose handy. I learned that the hard way on the durango. Didn't burn anything, but scared the living **** outta me.

[edit again] when I caught the durango on fire (2003), I was using WD40. Starter fluid burns quicker so probably not as bad lol.

 

[Rusty Nail]

In some vehicles, there is a little-known FILTER found in the bottom of the charcoal canister. 10mm socket to remove and the filter is behind the counter at O'Reilly's. They cost about two bucks.
Having removed the canister, flip it upside down and the filter should reveal.

Do yourself a favor and buy a new gas cap.

 

[1987 GMC Jimmy]

I didn't have time to check for leaks using a combustible. I do have a can of leftover throttle body cleaner from when I tuned up the Quad IV in my grandma's Pontiac. I'll do that this weekend. Unfortunately, I spent a good deal of time smoking out vacuum leaks about six months ago, my base gasket is newish, and I guess that leaves the intake. Maybe something's come up, but I try to scan for vacuum leaks when I'm under the hood. The more I think about it, the more the canister filter seems worth changing. I don't know the complete ins and out of the evaporative emissions stuff, especially on that mess of vacuum lines, purges, and check valves, but I do know that one time this summer, I had a gas pump shut off way prematurely on me so unless that was just a coincidence, there maybe something there just now rearing its ugly head. I guess it would have just been less ugly earlier. I'll do the gas cap, too.

 

[chengny]

I was pulling vacuum lines off my carburetor, and the fattest one that goes to the purge valve for the charcoal canister leaked gasoline out.

It isn't mentioned what carburetor you have installed, let's work on the assumption that it's a stock Rochester Q-jet.

If the line you refer to above is connected to the "T" port on the carburetor, that is the bowl vent to the canister. The evaporative emissions system collects vapors from two sources when the engine is off or cold - the gas tank(s) and the carburetor bowl. If you find raw fuel in the bowl vent hose, you might want to check that your bowl level is normal.

1984-87 Engines
This system Fig. 63, absorbs and stores fuel vapor in a carbon element until it can be removed and burned during normal combustion process. The canister is equipped with a vapor bowl vent control valve and a canister purge control valve which are both mounted on the canister.
The bowl vent control valve operates as follows:
When the engine is off, there is no vacuum through the vacuum signal tube to the valve diaphragm, spring tension opens the valve. Fuel vapors formed in the carburetor float bowl are pressurized to the point where they flow from a tube in the carburetor float bowl through a connecting hose marked ``Carb Bowl'' in the canister cover. Vapors travel past the open vent valve through the filter in the canister onto the activated charcoal, where they are stored until purging of the canister occurs. When the engine is running, vacuum is supplied through a tube marked ``Man Vac'' to the vent valve diaphragm. The diaphragm moves upward, raising the vent valve upward, against spring tension, allowing the valve to seal the passage venting fuel vapors from carburetor float bowl to canister. When engine is stopped, spring tension opens the valve to allow venting of the carburetor float bowl.
The canister purge control valve operates as follows:
Fuel vapor is inducted into the engine and is controlled by an orifice in the purge control valve. Ported vacuum signals to the purge control valve is controlled by a thermal vacuum switch (TVS) which delays purging until a specified engine temperature is reached. With throttle closed, the purge control valve diaphragm is seated by spring tension and no purging occurs. With throttle opened, ported vacuum is applied to the purge control valve. With vacuum applied to the diaphragm, the valve is opened when ported vacuum develops sufficient force to overcome preload of the diaphragm closing spring and purging takes place until the throttle is closed to a position which reduces ported vacuum to a level at which it can no longer overcome diaphragm spring tension.


Fig. 63 Purge valve type canister. 1984-87 carbureted models:

 

[Rusty Nail]

Jerry what do you do for a livin?

 

[chengny]

Nothing anymore. I am a retired marine engineer.

 

[1987 GMC Jimmy]

Okay, so I replaced the charcoal canister filter and the oxygen sensor. It seems that I've gotten rid of the codes, as well. Fuel cap's good and no vacuum leaks. I even did preventative maintenance on the some of the vacuum system. Here's the big overarching issue, though. I hooked the vacuum gauge up to it, and it read fifteen inches of Hg when the motor was ice cold and had just started. The idle was rough, crappy, and missy. There was also a very loud tick on the passenger side bank. After about a minute of running, the motor idled up, smoothed out, the tick went away, the miss went away, and the vacuum gauge instantly went up to 18 inches of Hg. It usually runs at about 19, almost 20, inches of Hg when fully warmed up. I checked the valvetrain on that side very closely. The adjustment is good and everything is moving as intended because I was trying to see if something was stuck. I was wondering if I have a lifter issue or something of the like. Besides a muffler that's degrading from the inside out, which I have a replacement for, my exhaust system is tip top. Oh, and here are pictures of my old canister filter and O2 sensor.

 

[Rusty Nail]

Damn. Little known indeed. Chances are your parts guy has never sold one.

It makes everything better.

 

[1987 GMC Jimmy]

I hope so. Thanks for the suggestion.