Facts about buzzing after the vehicle is shut off

DanW

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I've always known it was normal, but never knew exactly what it was, so thanks. I've listened to my JK do this for 13 years, so a similar sound out of the JL was not a surprise.
 

DanW

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That seems like a load of BS. I just searched Google and there is NO such solenoid that I can find related to the CP4 pump.

Anyone find this so-called solenoid?
Well, whatever it is, there certainly is a sound and I'm pretty sure we've all heard it. Lol!

I always figured it was something with the fuel injection.
 

BigGreen

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It's actually the government releasing their nanobot mind control 5g radiation. Diesel owners are specifically targeted because you hate the environment so much.
download.jpeg
 

Crawldad

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diesels are very picky about air or water in the fuel lines. they have return lines and the fuel is circulated through both filters and back to the tank. kinda like a fish tank lol. (not sure if the 3.0D has this same setup as the pickup trucks.)

like when you change the filters, you have to turn the key off and on 3 times for 3 cycles to purge all air out of the lines before starting.

maybe they put this in at shutdown so it starts easily in the morning.
 

DanW

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It's actually the government releasing their nanobot mind control 5g radiation. Diesel owners are specifically targeted because you hate the environment so much.
download.jpeg
Probably true. That explains my JK. It burns more oil than a diesel!
 

Gorilla57

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Well, whatever it is, there certainly is a sound and I'm pretty sure we've all heard it. Lol!

I always figured it was something with the fuel injection.
You have a gas motor. We are talking about a sound on the diesels. I have a 2020 Ram 1500 w the diesel, so I have the sounds that everyone has been talking about.
 

DanW

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You have a gas motor. We are talking about a sound on the diesels. I have a 2020 Ram 1500 w the diesel, so I have the sounds that everyone has been talking about.
Lol, well, the 3.8 JK gasser and 3.6 JL have buzzing sounds just like this, too, after shutoff. Not unique to the diesels.

But you are right. I didn't check which forum it was on. I reacted to the thread title because it described something familiar.

Carry on!
 

SteveSRT

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Interesting. I always figured it was the DEF lines clearing themselves so the fluid couldn't freeze or crystalize in them. Our 15L Cummins engines have always done that.
 

Gorilla57

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Interesting. I always figured it was the DEF lines clearing themselves so the fluid couldn't freeze or crystalize in them. Our 15L Cummins engines have always done that.
Yeah, or a coolant after run pump for the turbo.

The quantity solenoid is to meter flow from the lift pump to the injection pump to keep the fuel cooler and reduce “drag” on the injection pump. Why would they run the lift pump after you shut the truck down.....to cool the injector pump?
 
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