Engine Performance problem
1995 Ford F150 6 cyl Four Wheel Drive Automatic 100000 miles
I bought my F150 a few months ago. It has been driven very little the past several years (~1000 miles per year or less each of six years). I have done the basic tune-up and maintenance stuff and the truck has run great for the winter. At one point I found that the vacuum line from the intake to the charcoal canister was not hooked up at the canister. Assuming it fell of, I reinstalled it. The truck has ran several months (notably winter months) very well since then. The other day it started cutting out on me when I went to back up a hill. This got progressively worse until it would consistently cut out and even stall when I tried to go up a hill forward or backward. I checked the fuel filter and air filter to start with and changed the fuel filter just in case. Remembering that the line was off before I pulled it off again on a whim. This totally solved the problem. It seems to run fine like this. However after leaving the truck parked on a hill (rear/fuel tanks down) I noticed a fuel leak under the canister. The canister is now full of fuel. I did not notice it being full of full in the past and had no leakage in this area. The leak now is quite considerable. During the time the leak first showed up the selector was set to the rear tank (duel tank system) and both tanks were 1/2 to 3/4 full. It sat on this hill for about 2 days with ~35 degree nights and +70 degree days. Prior to the past few days I've been keeping the truck in the garage (limited temp changes and level surface). I'm assuming it is somehow drawing a suction on the tank due to thermal expansion/contraction, but this seems odd. Isn't the vapor line tied in up in the filler necks of the tanks? I can't see how fuel would be up that high. I haven't filled it with fuel in a few weeks and typically don't " top it off" too much.
Does the vacuum line from the intake go straight to the charcoal canister? If so you are missign the canister purge solenoid, this may be why it is sucking fuel from the tank into the canister.i will include 4 vacuum diagrams for the 6 cyl F-150. trace them down and se if you are missing anything.You will need to replace the canister once this is figured out, but not until thenm so it doesnt get filled with fuel as well
April, 16, 2010 AT 5:06 PM
Yes, the vacuum line goes straight to the intake. However, the vacuum line routing under the hood matches the third one you sent and it does not show a solenoid valve. I went looking for this initially after reading up a bit on this system and thinking this valve may have stopped working or.... With the engine running and warmed up, I could not feel or hear any vacuum on the line when I put my finger over the end...
I have attached a few pics to show some more details.
I parked the truck on the same hill last night, but with the back (tanks) up the hill this time. After about 24 hours the canister is dry and the level of fuel in it has not changed. It wasn't too cold last night....
April, 17, 2010 AT 12:18 PM
Try following the vapor line down the truck to see if there is any other valving on the vapor system. Some hook to the top of the tank
April, 17, 2010 AT 4:07 PM
I actually had someone else recommend the same thing. They mentioned and EVAP pump that pressurizes the tank. I traced the vent line all the way and found no valves, pumps. Etc. I can't see where it goes into the tank, but can feel it and it doesn't seem there is anything there either.
I rechecked the vacuum on the line between the canister and the intake (this time at higher rpm's than idle) and this time I for sure felt a vacuum, so this seems to be working as expected.
When I remove the fuel caps I do hear pressure escaping (presumably not vacuum collapsing, but I can't be 100% sure), however this doesn't strike me as excessive or anything.
I am starting to question if I didn't get the tank too full and the vacuum was able to suck some gas into the canister. Maybe I even did this a few times and eventually the canister filled up enough that it could suck some raw gas into the intake. This then was what was causing it to cut out when I tried to accelerate on a hill. I did notice some dark smoke one time when it was doing this, so this makes sense.
I'm not 100% convinced and like you said I'd hate to replace the canister only to have it fill up again, but I can't see what could have caused this. It's not throwing any codes and the emissions inspection in my area is just a visual for this age of vehicle, so I'm thinking of just plugging the vac line (can hook it up for the inspection) and letting it vent to atmosphere. I don't like to be too environmentally unkind and I imagine it might cut my fuel economy a bit, but. Maybe I can drain the gas out of the canister and hook it back up to see how long it works. Worst case it takes two seconds to pop the vac hose off if I have an issue again.
OK. Sorry, I'm just typing as I am thinking.
Any more thoughts from your side would be appreciated.
April, 18, 2010 AT 3:32 PM
Try drying out the canister and seeing if it fills back up again. It may not happen again, but yes I think you are right about it sucking raw fuel into the intake manifold, causing the bad running