Will a bad computer allow the vehicle to crank and crank but will not start. No spark at plugs, not power to coil packs. Can the computer cause this

Hello,

Assuming your spark plug firing order is correct after the coil pack replacement and your plugs and plug wires are clean and connected properly--and you have gas in the vehicle--I am thinking Throttle Position Sensor (TPS).
To test the TPS you hold the throttle pedal to the floor and start the vehicle, if the vehicle starts you need to clean or replace the TPS.

If the vehicle will still not start and everything was replaced on the vehicle as the parts came off of the vehicle--and the vehicle ran before think:
Compression: Washed cylinders (pull plugs and squirt clean oil in spark plug holes (one-two squirts).
Fuel: pull hose after fuel filter and crank vehicle
Spark: Pull plug wire and arc with screw driver when cranking engine. New coil pack could be faulty.

You may need someone to crank the vehicle (mind your hands) while you test. You should be able to find videos for spark testing.

I hope this helps.

it could be a bad crank sensor but it should have set the check engine light, check for codes anyway as there may be a code set. other things are bad ignition wires, coil pack, lose of power to coil pack, no ground for coil system, the PCM controls ground for the coils so it could be bad connection, bad coil drivers or just a PCM problem.

sounds like a bad crank sensor. it tells computer when its time to fire the spark

Hello and welcome to FixYa!
Please do check the battery if it's fully charged. If it's not, have it charged for if it's weak there will be insufficient current for the starter to kick the flywheel.
If it still fails even the battery is fully charged then the problem can be on the starter, ignition coil or ignition switch. I strongly suggest that you have it looked at for this will require an on hand trouble shooting by an expert mechanic.
Hope this helps and thank you for using FixYa! Have a good one!

is your coil pack bad replace coil pack there not getting spark on theses vehicles there coil packs each plug has one they go bad causeing the vehicle to run real rough and cause check engine light to come on mines the same way

Either the spark plug is faulty or the coil pack is faulty.The spark plugs get power to spark from coil packs.

If the engine has no spark, check for voltage at the coil positive terminal when the ignition key is on. If NO voltage, then problem is on the trigger side of the coil (pickup, crank sensor, ignition module or primary wiring circuit).

But If there is NO voltage at the coil itself, then in that case the problem is on the supply side (the ignition switch or ignition wiring circuit).

But if the coil has voltage, then problem may be a bad high voltage output wire from the coil to spark plugs or hairline cracks in the coil output tower.------Getting this all possibilities checked will point towards the exact faulty part which is to be replaced.----------This should help.Thanks.Helpmech.

You have three choices. First, check the spark and coil system to ensure you are getting a spark. Pull off a plug wire from the coil pack and crank. Have someone watch to see sparks snapping off the coil pack. If you don't have any replace the control module under the coil packs.

Second, you may not be getting enough fuel pressure. Put a gauge on the fuel pressure test port. You may have a bad oil pressure sensor, located down above the oil filter. Check that oil pressure sender and make sure the connector is pushed in. The power to the fuel pump runs through the oil sender. If the engine starts and oil pressure doesn't come up quickly, the computer will shut off the fuel pump. Check this and you can also manually engage the fuel pump from the relay block down by the passenger feet.

Third choice, and it's a long shot, check the harmonic balancer and the crank position sensor. If the sensor is bad, the computer has no idea when to fire the spark plugs. A magnet is on the harmonic balancer and flys by a sensor to induce a voltage in the coil and tell the computer what position the crank is in.

You also may have a bad computer.

You can figure it out.

A car that cranks over but doesn't start, in many cases will be due to a bad fuel pump, a broken timing belt, an inoperative cam sensor or crank sensor. Also this problems are related to faulty spark plug. Check the spark at spark plugs when you start the car. Do you notice any spark. Actually you should see. If in case there is no spark then it's a spark plug problem. Also the coil pack gives power to spark plug. So check the voltage at coil pack. It will show 12 volt.If there is no voltage noticed at coil pack then its faulty coil pack that has to be replaced.If all the possible options checked out ok then check the car starter. The starter gets power from battery to start the care. If the starter is faulty then it will not let the car to start. Also check and confirm that there is fuel in the car. If it very low fuel then in some cases this causes the problem. Also check and confirm that fuel pump is functioning properly and the fuel filter is not clogged. One of the easiest ways to check for a fuel pump related problem is to spray a little starting fluid into the air intake while trying to start the car. If the car starts momentarily, then there's a good chance the fuel pump is not working or the car is out of gas. You can also listen for the fuel pump's humming sound when the key is first turned on. Also if a inoperative fuel pump is suspected, a good technician will always check to verify there is power and ground being supplied to the pump, to eliminate the possibility of a bad relay or electrical issue. Fuel pressure can be checked with a pressure gage and if there is pressure, pulse can be checked at the fuel injectors in several ways including the most common, with the use of noid lights. If the injectors don't have pulse the engine won't start. ---------- This troubleshooting tips will help you to solve the problem.Thanks.Helpmech.

well if spark quits fuel usaly will to computer will do this to stop cadilac converter from filling with fuel!and causeing a fire saftey feature!!!!okay disconect battery wait a couple of minutes reconect! turn key on postion do not start or crank!off then on until you hear a GRRRRunt that is your fuel pump that is what you should hear turn your head to the right towards back seet and once you hear it that means pump is good then crank it then spark should quit if the coil packs a r bad then you have your problem if so test for spark also if you have eng light on cut the case hook up obd 2 scan find the fault and fix THIS IS WHAT I WOULD DO CHEERS!

There is an easy way to determine wether your getting spark or not. Take a plug wire off a spark plug and put it next to a solid piece of metal like a bracket (somewhere you can see the end of the wire sparking) hold the wire behind the connection point, and crank the engine (have someone help). If you see a spark, you are getting spark to the plugs, but may still have a problem with the coil pack. There is only one way to find out. Take the coil pack off, and look at it. There are two types of coil packs - 1 piece and three piece (others may be possible) on a three piece, you will need to have each one tested to determine whether it's bad or not. On a one piece, pull it off and look at the glue like material underneath it, that part is called the modular (the coil pack(s) will screw down to it. The modular may be bad, and may be able to test it as well.