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Dodgerench
Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3401
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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Submitted: 1 year ago.
Category: Dodge
Customer: replied 1 year ago.
06 Dodge Charger rt won't start. When I put in key. Lights turn on as normal. When I turn. It cranks but it won't turn over. While I'm cranking it. I hear sort of a knocking sound in the engine. It was just driving it perfectly fine . Until I stopped at a gas station.
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Dodgerench replied 1 year ago.

Hi, welcome to JustAnswer!. This is Ed.

I have to wonder if the car even ran again once you got to the gas station.

If you put fuel in it, but it never ran even briefly, we can rule out fuel contamination. On the other hand, if you managed to drive a short distance before the engine quit on you, contamination is a real possibility.

And the knocking sound...

Is that something you hear now while trying to start the engine?

Or was it doing that before the engine quit on you?

I'll be happy to take a phone call from you if you'd like to sort this out in person.

Talk in a bit,

Ed

Customer: replied 1 year ago.
When I got the the gas station I turned it off. Pumped gas. When I turned the key . It cranks and it seems like it's trying to turn over . But can't. It sounds like when it's almost trying to turn over. I hear a fast knocking sound . Then t just dies. I've tried turning it on many times but no good. I checked my oil pressure and it kept saying 0 in my instrument cluster. And the oil light stayed on when I tried turning it on. With research it suggested adding a quart of oil. Which I did but made no difference . I just got a oil change like 1 month ago.
Customer: replied 1 year ago.
It was driving perfectly find all morning before I stopped . I'm completely surprised:
Expert:  Dodgerench replied 1 year ago.

It can't be the fuel because your no-start happened too fast. You should have been able to drive a mile or two on straight water if that's what came out at the station.

Expert:  Dodgerench replied 1 year ago.

Which engine do you have? If you're not sure, shoot me the last 8 digits of your VIN and I can decode it from here.

Customer: replied 1 year ago.
It's a 5.7 v8 hemi
Expert:  Dodgerench replied 1 year ago.

Frankly, I'm surprised. I was pretty sure we were headed to a 3.5 liter engine timing belt issue. Hemi engines have actual timing chains and seldom just spit one out.

Are you near your car now?

If so, try this for me.

Hop in and try to start it like you normally would to begin with. If not successful, try pushing the throttle all the way to the floor while cranking. If it fires up, be quick to let up on the throttle.

What this does is to tell the PCM (engine controller) that you suspect a flooded condition and you'd like the injectors to shut off and that's just what this does. As soon as the engine passees 300 RPM, it will be running once again (cranking speeds are more like 150), so injector pulse is restored.

The only realistic reason I can imagine for your odd no-start was that your cooling system may be low. Lack of coolant will prevent proper circulation past the engine coolant temperature sensor, possibly rendering an incorrect reading that would be used for engine start. This sort of thing is most pronounced after taking a quick trip (like to the gas station) and shutting the engine off. As you sit there, the cold metal of the engine is not exposed to warmer coolant, so the PCM makes a decision to restart based on a colder engine temperature... which floods it.

Does this sound plausible? Had you driven 10 minutes or less from a cold start when this happened?

Give the wide open throttle (choke unloader) technique a try anyway and let me know what happens. If it fires up on its own, it may be because the engine has cooled and now truly matches its perceived temp.

Ed

Customer: replied 1 year ago.
When I tried starting it and accelerating it. It makes a knocking noise . The more I press the throttle, the louder and faster the knocking noise gets. Like if t was rods or something
Expert:  Dodgerench replied 1 year ago.

Oh wow. And all this happened between when you drove in to the station... turned the engine off... and tried restarting?

Expert:  Dodgerench replied 1 year ago.

If the engine continues to be very rough even though it's running now, I'm concerned that you may have broken a valve spring. It's something Hemi engines are somewhat known for, but it normally happens while you're driving, not restarting.

Expert:  Dodgerench replied 1 year ago.

And having a noise loud enough to hear inside the car... well ... suggests that you may have smacked a valve.

Let me describe what happens when a valve spring breaks and a valve hangs open...

Expert:  Dodgerench replied 1 year ago.

Engines are basically air pumps. Air comes in one end and exhaust goes out the other.

Air is high in oxygen content, exhaust is not.

Valves are used to keep air moving toward the exhaust side of the engine and preventing it from coming back.

When a valve doesn't close, it opens up a huge opportunity for oxygen-poor exhaust gases to be pulled back into the engine. Then this used-up air gets so far inside that it contaminates the intake charge for other cylinders, leaving insufficient 02 available to burn the fuel being injected (this is why the engine flooded).

More fuel continues to pour in, but can't be burned and at that point you have to do something like the choke unloader function. I cautioned you to lift off the throttle quickly for just this sort of reason; to prevent engine damage if a valve happened to be "swallowed" by the engine already.

You can't normally hear any mechanical noise when a valve spring breaks unless the damage is already done. I'm afraid this is one of those times.

You'll need to get a second opinion and an estimate, but steel yourself for a cylinder head replacement and probably one piston.

A second possibility for the noise you're hearing is that a steel valve seat came out of the aluminum cylinder head and that's what is bouncing around in the cylinder, making noise. The effects of a dropped valve seat are very similar to a broken valve spring in that your exhaust now mixes with the intake, but it might be a bit more expensive.