Flow of Raw gas in Charcoal Canister

[ejsharp]

Please pardon this transgression but I have raw fuel flowing into the charcoal canister on my 1990 Isuzu Trooper. I just bought the vehicle two days ago and the former owner said he just had a new fuel pump assembly installed.

What in heavens name could cause a regular flow of raw gasoline into the canister? The gas is flowing into the top through fuel hoses and then draining out the bottom of the canister.

Again please forgive this Isuzu transgression but I don't know where else to turn.

My deepest appriciation to anyone who could give me a lead as to what might be the cause.

[xp190]

You have to give some more infomration on this. Is this the charcoal canister that is used for filtering air, or the one that is a part of the fuel injection? Just to be clear, I'm guessing it's the second one for fuel injection, and if it is, that's very strange because only vapours are supposed to get in there unless they are condensing somewhere along the way, or the passage is cloged.

xp

[stevebfl]

The charcoal cannister is the main component of the evaporative emissions system. This system is charged with holding all the vapor from the fuel tank system. Gasoline has a very high vapor pressure and readily evaporates. Unburned hydrocarbons are said to be the greatest not from the product of combustion anymore but from the fueling process and evaporative emissions.

Since way back the tank has had it top vent lines usually gathered into a liquid vapor seporator that returned condensed liquid back to the tank. When this was overcome (buy high heat and the sloshing of driving) the vent gases proceeded through a device called a rollover valve. It could hold the weight of gas in a rollover (1-2 psi if I recall - this is the limit to the pressure you feel when removing the cap).

From the rollover valve the fuel vapors entered the top of the charcoal cannister. The bottom was open to air but to get there the vapors had to pass over a lot of vapor eating charcoal. if this were the end of it then the charcoal would eventually be saturated with fuel and the vapors would proceed right through into the atmoshere.

So, the system continues by having a fixed or variable volume devise attached to the intake which now sucks air in at the bottom of the cannister over the charcoal and picks up the fuel vapors. They are carried into the engine in amounts planned to be insignificant to fuel management.

So to have raw fuel coming out of the canister the vent line has gotten into raw fuel. I would be sure of the routing of the fuel return lines. I would also verify the purge line from the canister to the intake.

First I would like to say what a strange coincidence, I have a 91 Trooper and an 87 300E.

The evap emissions control canister stores fuel vapors from the gas tank when the engine is not running, and are purged when above idle, purge is controlled by vacuum and/or electric selenoids

You will want to check the purge selenoid vac lines and elec connections, if equipt, all vac lines to purge canister, it has the thermostatic vacuum switch in the intake manifold that may be bad, or the selenoid may be bad, or a line could be plugged.

Haynes makes a good manual for the Trooper, about $16 and well worth it.

I had the same problem with my '84 190e.What has happened here is that when the fuel pump was changed the return line or vent line was switched with the main fuel supply line.Ironically the car will still move but you'll be getting raw gas in your charcoal canister.After a while your car will start turng off when you do a sharp turn at moderate speeds.All you need to do is trace your main fuel supply line and switch it back .
Ede

[ejsharp]

You guys are truely marvelous. Each of you has answered very specific questions that I have regarding this most unusual situation.

I figure that who ever changed the fuel pump did a lot of guessing when he reassembled the system. Probably a guy who loved true and false questions when he was in school. He would be guaranteed 50% correct guesses. Beats a blank test return.

I first suspected such when I found that the fuel filter was installed backwards and I think what ede has said... that the fuel lines are switched somewhere along the line... is a correct diagnosis.

Inspector1... What a stroke of luck that we both have the same vehicles because I have no idea where these fuel and vacume lines are supposed to go. I have a Hanes manual for the Trooper but all the emmissions control info is for carberator version of the vehicle. I ordered the factory manuals for the Trooper and they are in the mail... both the electrical and mechanical including the updates.

There is one immediate question you could answer for me. One of the ports on the canister is missing a vacume hose... the one with the largest diameter and located to the extreme right when looking from the passenger side fender of the car. There is also no hose connected to the bottom of the canister.

Can you tell me what hoses are supposed to be connected to these points and where they should run to? I have the 4 cylinder I-Tec engine.

Sounds like we can be most helpful to each other in the future.

Again thanks to all for your most benificial input.

Originally posted by ejsharp
.

There is one immediate question you could answer for me. One of the ports on the canister is missing a vacume hose... the one with the largest diameter and located to the extreme right when looking from the passenger side fender of the car. There is also no hose connected to the bottom of the canister.

Can you tell me what hoses are supposed to be connected to these points and where they should run to? I have the 4 cylinder I-Tec engine.

Well, I dont have the Trooper with me at work today, I drove the 300E, ah what a car...so anyway, from your description it sounds like THAT is the important one, it is the vapor line from tank that has a check/relief valve in it, the check valve is to prevent liquid gasoline from entering the charcoal canister.If its the other one, now keep in mind I am looking at a diagram, not my Trooper, it may only be plugged off, or have another line going to the tank, both direct vapors from the tank to the canister.

The bottom port is to atmosphere, no hose

You might also replace the gas cap, as a non-venting cap can cause excessive pressure to build up in the tank causeing the canister to fill with gasoline.

If this doent fix the problem, then I can send tests for canister, purge selenoid (valve) and vacuum switching valve.

Oh, by the way, we are talking about the 4 cylinder 4ZE1 engine.

[ejsharp]

Well I found the problem. The fuel return line and the vapor line were switched at the gas tank. And the bare nozzle on the charcoal canister was missing the plugging cap. There is a diagram label on the hood that shows which of the canister nozzles gets capped. The engine now runs like a top and the canister is no longer spewing gasoline.

How I would like to say a few descriptive adjetives regarding the so called mechanic who installed the fuel filter on backwards and reversed the lines to the gas tank and fuel pump. He's not even a good guesser... got two out of two wrong.

Well the better part of the story is that I got the car for its donation value as a tax write off... $232.00... so I can't complain. I can see now why the former owner got disgusted with the vehicle.... he has recently put a small fortune into parts attempting to get it running right.

Inspector1... I can't find anything to tell me the type engine I have. I looked under the hood for some ID but no luck. I suppose it's the 4ZE1 like yours. It does have the I-Tec imprint on the intake manifold. Also Inspector1... keep in touch because I have the factory manuals for the Trooper now being delivered. So feel free to e-mail me for any info you might need in the future.

Again my thanks to everyone who helped out on this most unusual condition.

excellent!

Thanks for the offer of repair info, after almost a quarter million miles on my Trooper, which the kids call the Super Dooper Snooper Trooper, I was having a hesitation at accleration from a stop, I replaced the fuel filter, which had dark grey to black gas in it, and I think that has fixed it, I noticed only a slight hesitation once this AM before I put new gas in it. I am thinking that if this doesnt fix it then I am looking at the fuel pressure regulator next.

We have really enjoyed this vehicle and have 4 wheeled alot in the woods, we camp alot, and it has a great low range transfer gear, and I still get 20-22 MPG on the highway.

Have a good week end. JP

[ejsharp]

Another coincidence! I too have hesitation when accelerating from idle. That is my next project. I suspect it has something to do with the throttle setting. I'm still learning about things such as fuel regulator... in fact I'm waiting for the manual to get more info on it.

Will be checking things out further this weekend.

[ejsharp]

Well I spent the weekend under the hood and made considerable progress. The factory manuals also came on Saturday. The problem with the delay in acceleration is because the vacume system is not working. I use the term system because my 4 cylinder does not have airconditioning and it appears as though I have a combined selinoid that handles the vacume lines for both the fuel pressure and the high idle speed.

I determined that the combined selinoid was not funtioning by bypassing it completely and then rerunning the vacumes lines to a constant vacume situation.

All hesitation then disappeared and the motor takes off like a top when given gas from idle.

I first thought that I had solved the problem because I assumed the combined selinoid was bad. However I bench tested the selinoid by runnung 12 volts to it and both of the selinoids in the unit seemed to work properly... opening and closing the vacume lines.

And thats where I am right now. I am thinking about hooking all the vacume lines back to the selinoid again and then running 12 volts directly to the selinoids to see if vacume is activated for the components the vacume lines controll... in other words create a temporary situation where both the fuel pressure and the high idle operate. If my hunch is correct and the selinoids function with direct battery current, then that means the problem is with the current to the selinoids.

So I'm now off to the manuals to see where the current is supposed to come from so that I can trace the lines if necessary. (Sunday night)

Inspector1... Did you make any progress with your hesitation?

I too spent part of Saturday and Sunday under the hood, and let me tell you...what a puzzle this is turning out to be, I checked the timing-OK,dist. cap and rotor-OK, MAF-OK, WOT(?)-OK, my schematic shows a MAP and a TPS, but they arent there, or, if they are I sure cant find'em. ( I was wrong about what repair manaul I have, it's a chilton) Did not get around to the pres. regulator, as I thought I had the problem fixed when I got it to idle cold without stalling.

My throttle valve was very carbon'ed up so I cleaned it, that restored my idle speed, except it is now about 50RPM too high, ~ 1000 or so. The problem IS temperature related, as the problems happen when cold. So I am looking at the engine temp. sensor next, but I am also suspicious of the EVAP and selenoid as you mentioned, I know it sounds like I am all over the board with this, but after almost a quarter million miles, this is the first time I have had any problems, and I really have had no reason to even look for all these componants.

Do those new manuals you recieved have a trouble shooter flow chart in them?
If so, whats it have for hesitation at cold start?

Have a great day. JP

[ejsharp]

First some essentials:

Do you have a computer at home that can receive a photograph (scan) of a manual page?

Does your Zoo have airconditioning?

Do you have an email address?

To set your idle you should unplug the connector at your fuel pressure regulaor and plug the vacume line to the charcoal canister. Turn off any accessories... fan, AC etc.

Warm up engine to operating temp.

Then turn idle screw located on back of throttle housing. It can be seen well if you were to look from the front passenger seat.


I suspect that my problem is that the vacume lines to the combination selinoids have been switched around. They are not as the manual says they should be.

[ejsharp]

Inspector1... send me an email so that I can send some info to you. Your email is not listed for this forum.

Mornin' EJ,
No I have no PC with a scanner, my Zoo, which is what it is with 4 kids and 2 dogs in it, has AC.

The problem is getting really wierd, I set the idle and it is doing the hesitation cold and hot now, but I may have gotten a clue yesterday, which by the way, it acts just like an engine with water in the gas, but anyway, I gassed up yesterday and it started doing it worse ( again) but then I realized that it seems to have all started when I got gas at a certain station at pump #5, so I am thinking that the tank that serves this pump may have contaminants in it? I am going to put some heat in the Trooper tank this PM and see what it does.

My e-mail is jweeds@yahoo.com.

I sure appreciate all the help. And hey, I need new front tires for the 300E, do you have any input as to what are good, quiet tires reasonably priced?

Thanks