How much gas should there be in your gas tank before it runs out? I have a new 2010 Chrysler Sebring four-cylinder four-drive with a 16-gallon gas tank. The dealer verified this as did the owner’s manual. I have never run out of gas but have run it when the gauge symbol showed “gas needed.”

QUESTION: How much gas should there be in your gas tank before it runs out? I have a new 2010 Chrysler Sebring four-cylinder four-drive with a 16-gallon gas tank. The dealer verified this as did the owner’s manual. I have never run out of gas but have run it when the gauge symbol showed “gas needed.” Why when I fill it up does it take 16 gallons of gas? The most I have put in it was 16.3 gallons. What do you think about putting more gas in a tank than it should hold? I asked the dealer again and their response was “Don’t run out of gas!”


ANSWER: First and foremost, never let the gas tank go below one-fourth of the tank. The in-tank electric fuel pump sits in gas and is cooled by the gas it sits in. This is instant fuel pump destruction. Second, the way a vehicle’s computer system is designed, when the fuel level gets below one-fourth of the tank, the computer richens up the fuel mixture to prevent a lean condition. Third, running the gas below one-fourth will cause additional fuel pump and injector problems because of the fuel pump sucking air, not fuel. To the question of how much gas can you squeeze into a 16-gallon tank, just under 17 gallons if empty. Keep in mind the fuel fill tube also holds gas and you can overfill the gas tank and empty fuel into the evaporative emission system. One last thought; never overfill the gas tank in any vehicle. When the pump nozzle clicks off that’s it. Do not try to keep squeezing more gas in the tank.


 


QUESTION: Hello, I own a ’97 Porsche Boxster. The oil light comes on after the car warms up. The moment the idle raises it goes away then comes back when the idle lowers (car in neutral). It has just over 50K. Could the oil pump be going bad? I replaced the pressure sensor. Any advice would be appreciated.


ANSWER: It seems the oil pressure is dropping just enough to set the light on at hot low idle speed. The idle speed could be as little a 100 RPM too low. The engine bearing clearance could also be slightly more than original. My first suggestion is to use a 15/50 or 20/50 full synthetic oil for starts and see if the light stays out at hot idle. A slight amount of oil pump wear is also possible. If the light stays off with the oil replacement, I would not go any further.


 


QUESTION: I have a 2000 Camaro convertible with a 3.8 V6 engine. I purchased the car new, and now it’s got over 140,000 miles on it. I’ve been diligent about maintenance, and never encountered anything unexpected in terms of repair. Now, however, I have a problem that has me stumped. The car stalls at red lights, and nothing I’ve done seems to help. I’ve replaced the wires and plugs, the catalytic converter, the sensors that monitor oxygen intake – anything that’s come up with computer diagnosis, I’ve done. Two different mechanics have tried to find the problem without success. Any suggestions? Is raising the idle an option – my only option? Recently, it stalled when I took my foot off the gas at 30 MPH approaching a red light, so I think it’s getting worse. I love the car, and had planned to keep it forever. Help!


ANSWER: The most common problem you are having is the idle control motor is not maintaining the idle speed. I see this problem often on various makes and models without setting a computer fault code. A technician can hook up a professional scan tool and actually watch the idle motor in real time to verify the operation. Another possibility is the EGR valve not sealing. This would allow unmetered air to enter the engine and cause a lean condition. Last is a dirty throttle body is also common cause for engine stalling.


 


QUESTION: I just bought a 1983 Ranger and did a tune-up on it and a new air filter and belts and now it’s backfiring out of the carb. It’s a 2.8 v6 with a four-speed manual transmission and it’s spitting and sputtering as it revs, and when it’s hot out it stalls on me and takes a bit to restart. I hope it’s not the carb and it’s just out of time but can you please help me? I do all the work myself on anything I own. I just can’t figure this out and don’t want to spend 300-plus bucks on a new carb.


ANSWER: The first question is did the tune-up create the problem? If it happened after you replaced the tune-up parts you could have a sparkplug wire crossed. If the firing order is correct the next step is check the carburetor to make sure fuel is not leaking from it. The EGR valve also has to be checked to make sure it is closed all the way. A compression test may also be required. If equipped with a distributor cap it too needs to be checked for cracking.


 


Junior Damato writes weekly about cars. You can send questions to him care of the Old Colony Memorial, 182 Standish Ave., Plymouth, MA 02360.