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Nissan Repair/General Troubleshooting


Hi Calvin,

I have a couple very quick (I hope) questions, relating to cars in general, and not any specific make or model.  

1: Ignoring the fuel gauge, how can you definitively tell if a car is out of gas as opposed to having a fuel pump problem?

2: What is the best way to tell the difference between a dead battery and an alternator issue?

Thank you very much for your time and assistance.

Best regards,


Hi Mick -

1. Usually when you turn the ignition on you can hear the fuel pump for a few seconds. most cars these days the fuel pump is in the fuel tank, so you would have to listen closely, preferably have a helper. So if you hear the fuel pump but no fuel at the engine side, then you are out of fuel. Conversely, if you do not hear anything, I would check the fuel pump or related fuses and relays.

2. You will need a volt meter for DC voltage. A good battery when idle puts out 12.6 volts. Anything less than 12V, you should replace the battery. When you start the engine and turn on the headlights, the battery voltage reads at least 14V, but not more than 16. This tells you that the alternator is working properly.

Hope this helps -

Nissan Repair

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Calvin Iwashita


All general car repairs for all models of vehicles, except technicals (overhauls) on A/C systems and transmissions.


16 years as a car mechanic from 1974 to 1990, and still repair cars on the side.


High School and college graduate

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