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hard starting when gas tank low

edited July 2011 in The Show
I want to confirm what the lady with the Honda Civic was saying. I have 1998 Civic that I've been driving for about 7 years, from 120K to 255K miles.
I usually let the fuel tank run down low before refilling, at 1/8 of a tank, if the car sits for a more than a few hours, it has to crank over a while to start, like 6-7 seconds. If it has >1/4 tank, either morning or after work it starts no problem, with only 1-2 seconds of cranking.

So it seems to be some kind of pressure bleed out of a one-way check valve or loss of pump prime or drain-back problem of the fuel pump? So it takes time to pump the fuel (or fuel pressure) back up to the engine. BUT only after the fuel drops to some critcal level...

I disagree with Click & Clack, the difference in pressure head between 1/2 tank versus 1/8 tank would be a few inches, that's a tiny pressure head difference. Hard to believe that could affect the starting.


  • I have an 03 Civic (65K miles) and have noticed something quite similar. In general, it starts like a charm, but when the tank is v. low and the car has been sitting for while, I have to hold the key down for an extra 1-2 seconds before it'll start. I told my mechanic this, and he looked at me like I was crazy. "You're imagining it. The amount of gas in your tank won't affect how fast your car starts", he said. I felt sorta vindicated hearing this woman call in.
    It's sounds like this issue might be fairly specific to Civics. I wonder if this is some kind of design flaw. Should we inform the good people at Honda?
  • You probably have a fuel pump that's getting a bit weak and the difference in pressure head between a full and near empty tank is enough to make the difference. You have to remember the design margin on cars is very small. The pump when new is just large enough to do the job, even on a Honda.
  • No stations will carry Car Talk where I live, in the North Georgia Mountains. I therefore have to listen to it on my computer. I have just finished listening to the most recent show during which a lady described how the engine in her Honda seems to be reluctant to start running when the fuel tank is low and more eager to start when the tank is full. This triggered a memory in what passes for my brain. In the seventies, my ex and I bought a 64 or 65 Pontiac from a friend who owned a garage. He told us that he had helped one of his ex-employee mechanics get the car. He said the car did not run when they got it. He allowed the mechanic to do a complete rebuild of the engine, a 400 cid, with a two barrel carburetor. The rebuild was done after hours, using parts the owner supplied. The mechanic turned out to be an alcoholic and was fired right after the engine was finished. When we got the car the engine was sort of reluctant to turn over when cranking. Once it started cranking, it fired right up and ran well. The garage owner told us that the engine was not broke in yet as all of the parts were brand new. He said it would crank better after it had been driven a while. That never happened. My wife was the primary driver of this car. One night, we were going out and decided to use her Pontiac. I got into the driver’s seat. I turned the key to start. The engine went Urrrr, urrr, urrr and in general gave me the impression the battery was on its last legs. I turned to her and said, “It’s got a dead battery.” She said no, just push the gas pedal to the floor while you crank it. I said, “No way is the gas pedal connected to the starter or charging system.” [I also probably thought silently about crazy women.] She repeated her stupid instruction. I ignored her and tried to crank it again. Same result. Then I thought what the heck, and pushed the pedal to the metal and hit the crank. The thing cranked like a brand new car and fired right up. It was the same every time one of us drove it as long as we had it. I have wondered for years why that worked.
  • OMG, I’m not crazy after all! When I heard Jennifer’s car problem, I knew exactly what she was talking about. My car does a very similar thing, and the dealer thought I was nuts.
    Different car, slightly different scenario; same problem:
    I have a 2002 Volvo S60 (90k miles). I never had a problem until 2006 when I got married and moved to my husband’s house. There was no room in the garage so I had to park my car in the driveway, which slants downward. If my gas tank gets below ½ full, the car won’t start in the morning. Imagine my surprise the first time that happened! If I add gas, it will start. My husband suggested rolling the car to a flatter location (inside the almost full garage), and that works too.
  • ...or better yet just back into the driveway so your car is facing uphill.
  • A friend has a '88 VW Fox, which had a similar problem: "Sometimes it won't start. Its not the fuel pump. It has already been replaced", he said. The problems would only occur if the tank was less than half full. I agreed to help him repair it.
    Turns out the VW Fox has two fuel pumps: One inside of the tank and a second one mounted next to the tank for generating the high pressure needed for the injectors. The pump inside the tank feeds the second pump.
    We disconnected the fuel line outside of the gas tank and measured the fuel output rate if the first pump. Zero.
    The pump inside the tank had failed, and the output hose of this pump had rotted out within the fuel tank. If the tank was full there was sufficient pressure for the outside pump to get gas. But once the fuel level fell below the rotten hose the outside pump got air, causing the engine to run rough and to not start once stopped.
    Replacing the pump and the hose solved the problem.
    Some cars have multiple fuel pumps, check all of them, and check for a bad suction hose within the fuel tank.
  • Jennifer is not crazy, her boyfriend is. I have a 1992 Civic SI Hatchback which does the exact same thing; turns over longer before starting when it's really low on gas. It actually serves as a reminder for me to fuel up right away......
  • edited August 2011
    This problem is something you just have to deal with when you own a small Japanese car. It's not a leak or a malfunction. It happens in almost all small Japanese cars, and the solution is simple:

    When you are ready to start the car, don't start the engine right away. Turn the key to the "on" position and wait a few seconds for the fuel pump to pressurize the system. Sometimes, you can actually hear the fuel pump activate and shut off. Once the fuel pump shuts off, turn the key to the "start" position, and it will start right up every time, even if the tank is really low.

    Doing this will help your starter last longer. This is also the process used for starting big rig trucks.
  • edited August 2011
    "This problem is something you just have to deal with when you own a small Japanese car. It's not a leak or a malfunction. It happens in almost all small Japanese cars, "

    Whitey, where in the name of Hades did you get this idea from? Would you like to explain to me from a technical standpoint exactly why it is that you think all small Japanese cars have this problem, what from a technical standpoint the problem is, and why turning the key to "on" every time before starting it?

    Or, worded differently, exactly why do all small Japanese cars suffer from this? And what does it mean?
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