My nissan sentra will crank over and tries to start but will not start.Just last week it started to chug a little after turning the key and then ran fine,now it will not start at all.

Without very much information provided, I would focus on the Crankshaft Position Sensor.

Dear TxGreaseMonkey, I just replaced the spark plugs 1 month ago and when I did it started right up,so I thought that was good until my wife told me she was having problems again by that time it was to late.

What year Nissan Sentra and what engine do you have?

It is a 2004 1.8 liter 4 cyl

. Remove and fully charge the battery. Most auto parts stores will do this for free.

. Test all under hood and under dash fuses with a test light or multimeter:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post252145

. Test for codes.

. Test for spark.

. Test for fuel. Can you hear the fuel pump run, when the ignition switch is turned to ON?

. Replace the Crankshaft Position Sensor, if the problem persists. Very inexpensive on this engine. The Crankshaft Position Sensor and the Camshaft Position Sensor are interchangeable. Easy job.

Are the new spark plugs the exact same brand and plug no. that came in the car?

Yes they are pretty close to the same but better, as in spark plugs go, I never heard or did I check to hear if the fuel pump was running .Where would I find the crankshaft position sensor and the camshaft position be located.

When you say pretty close to the same, but better, what do you mean? Crankshaft Position Sensor (CKP) should be located next to the crankshaft. The CKP is usually the culprit, due to its exposure to the elements.

The plugs that were in the car are NGK R plfr5a and the plugs I put in are DENSO PLATINUM TJ PKH16TT 4505.

Are them plugs OK? Im having problems finding them sensors, could you tell me what and where to look. Thanks.As you can tell I am no car guy by any means.

The new plugs may be the wrong ones. I don't see those listed for your engine. That can be a show-stopper. Are you sure they are Denso and not Bosch? I'm definitely not a fan of Bosch plugs--way too many problems. It's best to use the exact plugs that came in the engine.

The Crankshaft Position Sensor is likely under the car, just in front of or behind the crankshaft. It should be held on by one bolt. See what it looks like online first and then look for it--go to AutoZone.com.

Are them plugs ok? Im having problems finding them sensors, could you tell me what and where to look. thanks.As you can tell i am no car guy by any means.

Yes they are DENSO PLATINUM PKH16TT 4505. Also when I get the car jacked up is the sensor hard to get to ?

When you say pretty close to the same, but better, what do you mean? Crankshaft Position Sensor (CKP) should be located next to the crankshaft. The CKP is usually the culprit, due to its exposure to the elements.

DearTxGreaseMonket. Iwent on line to autozone.comm to find a crankshaft and a camshaft sensor and they could find no matches for thoses items.

Camshaft Position Sensor:

AutoZone.com | Vehicle Selection | Year (http://www.autozone.com/autozone/catalog/parts/partsShelf.jsp?categoryDisplayName=Internal+Engine&fromType=parts&fromString=search&parentId=51-0&currentPage=1&filterByKeyWord=sensor&isSearchByPartNumber=false&navValue=15100111&categoryNValue=15199999&fromWhere=&itemId=111-0&displayName=Crankshaft+Position+Sensor&searchText=sensor)

You may also have installed the wrong spark plugs--check it out thoroughly.