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So I have a 1987 Hyundai Pony that was a little stubborn starting last time, but did run in the end. Then it sat for a couple of weeks. It's kind of cold (but not that cold—I'm in Vancouver). Now nothing seems to make it want to start. There's plenty of gas in the tank, the starter motor is cranking fine, it seems to be sparking fine (I pulled one plug out to check, didn't look at the other three though).

I remember someone telling me that when the ignition is first turned on you should be able to hear a hum of the fuel pump running for a few seconds. I don't hear anything like that. But how likely is it that a fuel pump problem would arise from the car just sitting for a couple of weeks? I don't really want to replace the thing if that's not the problem. Is checking the fuel line pressure a straightforward thing?

Thanks very much for any ideas!

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3 Answers

I fixed a 1998 Ford Contour that wouldn't start after sitting for a while in cold weather. The problem was a corroded ground connector in the wiring at the fuel pump. A couple years later, it was left sitting again, and sure enough, it wouldn't start. Same problem, same fix. It can happen, though I'm not sure I would have believed it if I hadn't seen it with my own eyes.

You should be able to hear the fuel pump briefly after turning the ignition key to the accessory position. If you don't, the first thing to check is the fuel pump relay. The location should be in your owners manual, it's probably in a box in the engine compartment with some fuses and other relays. Swap the relay with a known good good one. You might be able to feel the relay engage if you have your finger on it when it gets power (don't start the engine, just turn the key to the accessory position).

Once you've ruled out the relay, it's probably time to check for fuel pressure. If you can get your hands on a fuel pressure test gauge, check it at the fuel rail under the hood, there should be a test port. You can rent the gauge from some auto parts stores. This is the "least likely to start a fire" method of checking the fuel pressure, and the only one I'd recommend.

If the pressure is low, the pump may have one foot in the grave, and if it's zip, you've got a dead pump or a problem with the wiring between the relay and the pump. I suppose you could have a clogged fuel filter too, that's worth checking, just be careful when disconnecting the fuel lines. Since your vehicle hasn't been running, you don't have to worry about hot exhaust components, but disconnect the battery for the sake of safety and be careful not to generate any sparks. Also, be prepared to deal with a bit of spilled gasoline (and don't catch it in the face). Might as well change the filter while you're down there.

If the fuel pressure is good (you need to find out what the expected value is), your problem is not the fuel pump. If you're getting spark and fuel but it still won't start, it might be time to check the timing.

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It's more likely to be the relay than the fuel pump. And the run-on of the fuel pump is much more likely to be heard after cranking, rather than just when ignition is enabled. You don't want the fuel pump to be running if the engine isn't turning over as that creates a fire hazard should you be in a crash. I know of several cars configured like this and the fuel pump relay is an integral piece of this safety feature.

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Two questions, since you checked your spark plugs for spark...

  1. Can you get to your fuel rail on top of your head?
  2. If so, can you disconnected?

I ask, because the "poor man's" way of checking the fuel pump is to disconnect the fuel rail and see fuel coming as soon as you turn the ignition to the accessory position. Listening for the pump can be difficult sometimes, but ensure that you do not crank as the ignition will spark and can cause the fuel to ignite. Most vehicle will pump fuel for ~5 seconds to ensure there is enough to start, as it drains overnight/after sitting for long periods.

DO NOT ATTEMPT THIS IF IT DOES NOT MAKE PERFECT SENSE.

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You normally disconnect the ignition coil to do this, though this may be tricky on newer cars with more complicated ignition. –  staticsan Dec 19 '11 at 4:37
    
True. Some also have multiple coil packs, so I wanted the no start. –  FossilizedCarlos Dec 22 '11 at 4:23
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