Car randomly wouldn’t start No spark?

Tiny
NIHAL
  • MEMBER
  • 2009 BUICK ALLURE
  • 3.8L
  • V8
  • AUTOMATIC
  • 210,000 MILES
A few months ago, the car randomly wouldn’t start. It was a crank no start. I looked online and checked the fuel pump which was fine and had a no spark issue. I replaced the spark plugs, and it was the same. Then I replaced the coils which didn’t solve the issue and after that I replaced the control module which fixed the issue. The car worked for about 2 weeks before the same thing happened. The fuel pump is fine and I’m not getting any spark. I replaced the module and this time it didn’t solve the issue. The module is getting power but isn’t giving power to the spark plugs. I took apart the fuse box and all the wires and ground connection seemed to be fine. All the fuses and relay are also fine. What could my issue be?
Thursday, December 26th, 2024 AT 1:37 PM

25 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Have you checked the crankshaft position sensor? If it has failed, it will prevent spark to the plugs.

First, if you have a live data scan tool, check for an RPM signal when cranking the engine. If you don't have a scanner, see if the tachometer moves a little when cranking.

If there is no signal, replace the crankshaft position sensor. I attached the directions below specific to your vehicle.

Check for a signal and let me know what you find.

Take care,

Joe

See pics below.
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Thursday, December 26th, 2024 AT 10:21 PM
Tiny
NIHAL
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I used a obd2 scanner and it doesn’t show me any codes for crankshaft position sensor, but I will try your method. Thank you
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Friday, December 27th, 2024 AT 9:53 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

The sensor can fail and not set a code. Because a crankshaft position sensor is related to engine speed, when it fails, it may not trigger a CEL light. This is because some things can stop the crankshaft position sensor's signal that will have nothing to do with the sensor going bad, such as running out of gas or stalling the engine when letting the clutch pedal out too quickly.

Take a look through this link:

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

Let me know your thoughts and what you find.

Take care,

Joe

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Saturday, December 28th, 2024 AT 8:54 PM
Tiny
NIHAL
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  • 15 POSTS
I took the crankshaft sensor out and I tested it using a multimeter and it was fine but I took the camshaft sensor, and it turned out to be bad so I ordered one and should be here in a few days and hopefully fixes the issue. Thank you for your help.
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Saturday, December 28th, 2024 AT 9:10 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Thanks for the update. If that doesn't resolve the issue and you have a live data scan tool, check to see if there is an RPM signal when cranking the engine.

I suggest checking because loss of ignition spark is usually the result (not always) of a failed crankshaft position sensor.

Let me know how things work out for you.

Take care,

Joe
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Saturday, December 28th, 2024 AT 9:46 PM
Tiny
NIHAL
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Hi Joe, the camshaft position sensor didn’t do the trick, and I checked the crankshaft position sensor using a multi meter and it is working. Next, I will try and replace the electrical part of the ignition switch because I heard that may solve it.
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Sunday, January 5th, 2025 AT 3:59 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

I'm not familiar with an issue with the ignition switch. Anything is possible.

I attached a technical service bulletin (TSB) below for your review. It is related to the use of non-OEM ignition parts.

Last, I need confirmation that there is power to the coils. See the last pic below. Check the fuse with the ignition key in the run position. If it has power, go to the module and check if power is present at the pink wire.

Let me know.

Joe

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Sunday, January 5th, 2025 AT 9:52 PM
Tiny
NIHAL
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Hi Joe, I checked the fuse, and it is good and there is power going to the pink wire. I used a test pen to check it. But when I put the test pen on the module there is no power. Thanks for your help.
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Sunday, January 5th, 2025 AT 9:58 PM
Tiny
JACOBANDNICKOLAS
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If you have power at the fuse, the wire must be broken between the fuse and the module. Power comes from the powertrain relay in the under-hood fuse box and to the fuse you checked. If that has power, then the relay is working.

If you have power out from the fuse, it goes directly to the control module. If you can, disconnect both sides of that power supply and check it for continuity. We must be missing something simple.

Let me know.

See pic below (ignore the first pic. I can't delete it)
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Sunday, January 5th, 2025 AT 11:29 PM
Tiny
NIHAL
  • MEMBER
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Hi Joe, sorry for the late reply, I’ve been a little busy. The wire can’t be broken since the module is getting power from the fuse box. But the spark plugs are not getting any power. I’m going to try and put the old module in because of what you said about non OEM parts not working and see if that solves the issue. If not, then I will get a ignition switch because I saw some videos online saying it could be that. Hopefully the car will get fixed soon. This is 1 hour after I posted the first reply and I’m editing it now. I worked on the car and noticed that when I plugged the ignition control module that I could hear and see the spark on the coils and that would only happen sometimes. I also noticed that when it did the spark the RPMs went up to 3k and the fuel pump turned on and off. I don’t know what that means please let me know.
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Sunday, January 12th, 2025 AT 11:38 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,348 POSTS
So to recap, you replaced the crankshaft sensor and the ignition control module? I crankshaft sensor can test good with a multimeter but fail during the engine operations. Also, no trouble codes? When the engine stalls you are certain there is no spark correct?
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Wednesday, January 15th, 2025 AT 9:42 AM
Tiny
NIHAL
  • MEMBER
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No I am going to replace the crankshaft position sensor but replaced the camshaft position sensor and also replaced the ignition control module. I also replaced the spark plugs as well as the coils. The engine cranks but doesn’t start and there is no spark. The spark only happens when I unplug the control module and plug it back in. As I plug it in I can physically see and hear the current on the module. But when I go to start the car, the spark stops which causes it to not start.
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Saturday, January 18th, 2025 AT 4:27 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

When you lose spark, check to see if there is an RPM signal. You can do this with a live data scan tool or watch the tachometer to see if it moves a little.

What you described surely sounds like a faulty crankshaft position sensor. Take a look through this link. Let me know if you feel it mirrors what you are experiencing.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

Let us know.

Joe
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Saturday, January 18th, 2025 AT 6:53 PM
Tiny
NIHAL
  • MEMBER
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I replaced the crankshaft position sensor, and the car still does the same thing. I am going to try and replace the ignition switch to see because that’s the last thing I can think of. Please let me know if it can be something else.
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Sunday, January 26th, 2025 AT 2:43 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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This is a tough one. However, you mentioned there is no power to the module when this happens, but you still have power at the fuse. That, in my mind, indicates it isn't the switch, but anything is possible. I suspect a broken or damaged connection between the fuse and the module. Let me know your thoughts.

Joe
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Monday, January 27th, 2025 AT 6:20 PM
Tiny
NIHAL
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No there is power to the module, but the module isn’t giving power to the spark plugs. I don’t know what the case could be.
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Monday, January 27th, 2025 AT 6:54 PM
Tiny
JACOBANDNICKOLAS
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Hi,

If you aren't getting power to the module, is won't work. We need to try jumping power to the module to see if that allows it to start in these conditions. Also, the next question would be where is the power being lost?
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Monday, January 27th, 2025 AT 7:45 PM
Tiny
NIHAL
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The module is getting power and all wires are intact.
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Monday, January 27th, 2025 AT 7:46 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Sorry about that. I misread your last post.

Make sure the ICM is grounded. At the connector, there is a black wire with a white tracer. That grounds to the front top of the engine. Make sure it is a solid chassis ground.

Next, there will be a red wire with a black tracer. That is a signal ground from the PCM. Confirm that is producing ground. When cranking.

The white wire is from the PCM. It is the ignition timing control signal. That should be producing a signal as well.

If these things are not present, I have a feeling the PCM is faulty.

Let me know.

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Monday, January 27th, 2025 AT 8:02 PM
Tiny
NIHAL
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Okay, thank you. I will look into this tomorrow morning.
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Monday, January 27th, 2025 AT 8:07 PM

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