Question2004 Chev S-10 ZR5 4WD with 19K miles on original 4.3L V6. Eight weeks ago engine stalled while driving about 45mph. Gas guage showed little less than a quarter of a tank with temps around 85. Filled tank full. No problems until tues this week. Between one half and one quarter tank stalled at intersection. Put in about 4 gal to about one half a tank. Would go about a mile or two and stall. Stopped and filled the tank. All fine till thurs. About one half a tank it stalled at intersection. Filled it up all ok.I watch my mileage driven and match the amount of fuel used to what it takes to fill. Gas guage accurate.Dealership states could be fuel pump or computer, both could cause these symptoms. Temps this week over 100 degrees and problems occured after about 30 miles interstate drive at 65mph and three miles at 45mph. Truck stalled within quarter mile both times on about a 10 degree uphill grade. My thoughts are if it's the fuel filter the problem would not settle at around one half tank. If it's the fuel pump wouldn't it give me problems at all levels of the tank not just around a little under one half tank? All help appreciated.
Answerfirst try drygas. This will disolve any water that may have gotten into the tank. When you get low, you start sucking up the 'junk' at the bottom of the tank.
I think it is vapor lock. The temperatures combined with the fact that at 1/4 tank, the tank is mostly vapors, I think you are vaporlocking.
Get this, if you take a portable gas can and fill it up. Then seal it up except the pour spout. Then turn it upside down. The pour spout does not just pour the gas out, but rather it plops out in spruts. when it gets emptier the sides of the can start to suck in and the plops become less frequent. You actually may get one plop every 5 seconds. If you would have opened the little breather hole, the gas would have poured out all at once and rather quickly. The reason is you vented it.
Where does a fuel tank vent? Two places. Out the purge canister through a computer controlled purge valve (which probably failed on you), and through your gas cap. Well with today's emission concerns, they stopped venting at the gas cap and you are solely at the mercy of the purge valve. These fail regularly.
Once the tank is mostly empty, the pump cannot pull the gas and send it on. Then you open the gas cap and vent the tank. This allows a few more miles until the vapors overcome the pump again. Then you fill it up and the vapors are not an issue.
Here is an experiment. Next time you get low and the van stalls. Simply unscrew the gas cap and see if it act okay again. I bet it will. Now you can suspect the purge valve.
Replace the purge vavle??? Cheaper and easier to just get a new gas cap. One that vents. You may emit a little to the atmosphere, but not enough to feel guilty about. About the same amount as an open can of gas stored in your shed.
