Hi i have a ls400 it will turn over but wont start. it might not be getting spark to the spark plugs. i checked 3 of 8 of them and they are NOT getting spark. ive had the car for a week but was running strong and starting every time. any ideas of why it isnt getting spark to the spark plugs?

What are the symptoms of "won't start?" Do you get a single click (relay/solenoid/wiring issue) when turning the key to the Start position? Do you get a rapid series of clicks (low battery)? Do you get no sounds? Do dash lights come on as expected when in the Run position? Have you tried shifting to Neutral (assuming an automatic transmission) and attempting to start? What is the make, model, and year of your vehicle?

-Rod

check for spark by putting a screw driver in a plug lead and wind it over,a spark should jump to earth if you hold it close to the motor.Check that it has plenty of fuel pressure.

Hi, Sound like you have the firing order wrong try changing the plug wires around or look on side of engine it normally is marked just below the spark plugs the numbers give you the firing orders IE: 1 2 3 4. Hope this helps give me feedback please. Thanks, Malcolm Campbell.

Okay, I am not convinced it is the spark. But there is a chance. The fact that torching the plugs allowed it to start tells me you engine is flooding. Do you smell gas? If you open the throttle body with the air cleaner off, does vapor come out when the engine had recently cranked? If it is electrical, then power to both ignition modules is failing, which means A. the ECM is not providing power to the modules, or B. The engine crank sensor has failed. The Cause could be a bad connection to the ECM.
A scope will indicate whether or not the proper pulses are being input and output from the ECM to the modules. Of course it will need to be tested when it is not working compared to when it is. When cranking, the tach should move indicating rotation of the crank, if not, there is a good chance the crank sensor is no good.

Check fuel pump fuel pressure , if no pressure change fuel pump .

If the spark is getting right.Get the fuel system checked.Its quite possible that fuel pressure is low or fuel pump not starting up right.

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CAR NO START PROBLEMS:-----

It can be the issue with weak battery or faulty battery or if battery is ok,then its faulty starter causing the issue.

From start to end troubleshooting these problem i suggest you to click the link below and follow its procedure:-----

What to Do When Car Turns Over But Won't Start?

http://technoanswers.blogspot.com/2012/11/what-to-do-when-car-turns-over-but-wont.html

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Car starting issues?

http://technoanswers.blogspot.in/2012/02/car-starting-issues.html

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Car Starting Problems

http://whoisbyme.blogspot.in/2012/06/car-starting-problems.html

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1991 Toyota Trecel: Engine Starts fine but dies when gets Warm?

http://whatisbyme.blogspot.in/2012/05/1991-toyota-trecel-engine-starts-fine.html

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1994 Toyota Pickup: Starts fine but dies in few seconds?

http://howtobyme.blogspot.in/2012/05/1994-toyota-pickup-starts-fine-but-dies.html

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1999 Chrysler Cirrus: 8 IGN Fuel Starter Fuse Blows?

http://whatisbyme.blogspot.in/2012/06/1999-chrysler-cirrus-8-ign-fuel-starter.html

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2001 Toyota Camry: No start After replacing Battery?

http://whatisbyme.blogspot.in/2012/05/2001-toyota-camry-no-start-after.html

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1989 Toyota Pickup Truck: Turns over but not start?

http://whatisbyme.blogspot.in/2012/05/1989-toyota-pickup-truck-turns-over-but.html

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Car dead and will not Start?

http://whatisbyme.blogspot.in/2012/05/car-dead-and-will-not-start.html

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1995 Lexus LS400: Running Hot?

http://whatisbyme.blogspot.in/2012/05/1995-lexus-ls400-running-hot.html

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2001 Toyota Prius will not start?

http://whatisbyme.blogspot.in/2012/05/2001-toyota-prius-will-not-start.html

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1996 Jeep Grand Cherokee: Engine will not start?

http://repairhelpcenter.blogspot.in/2012/06/1996-jeep-grand-cherokee-engine-will.html

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Mitsubishi will not start

http://www.howtorepairguide.com

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These will help.

Thanks.

Thanks for the clarification. Engine needs 3 things to run. Compression , fuel , spark.
It's turning over so you have compression.
Check a couple of spark plug wires for spark.
If you got spark , most likely no fuel.

Was it running before the "tune up" ?

Hi,
You can pull a plug wire end from a plug and either put a spare plug in the end, or remove one of your plugs from the engine. Just lay the plug onto the engine... don't hold it... ha
Have someone turn the engine over and observe for spark at the end of the plug.
This will at least determine if you're getting spark. Good luck!

ok, i tell you 3 possible causes.
check maf sensor connection , check fuel pressure regulator (max press fuel in rail 40 psi) , check engine compression (min 95 psi ) if less this cause spark plugs wet and not start

Have you checked if it has spark ? Check the spark by removing a sprk plug and connect it to the wire. Place the spark plug agains a groung. Then have somebody crank the engine. It should have spark.