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> Knock Knock, Sound Just At Starting
windforfun
post Nov 22 2023, 05:39 PM
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Does your 1.7 make a knocking sound just at starting? It happens just before the engine starts to run. Mine has always done this & I can't find anything loose or anything hitting anything within the engine bay. Normal? Thanks.

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Root_Werks
post Nov 22 2023, 05:49 PM
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See if you can get a video of start up for us.

Anything knocking at any time usually isn't good.

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rjames
post Nov 22 2023, 06:05 PM
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Do you have hydraulic lifters?
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914sgofast2
post Nov 22 2023, 06:12 PM
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Are you hearing the fuel pump's initial pumping sound to prime the injectors with gas, before the engine even fires up? If so, that is normal.
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windforfun
post Nov 22 2023, 06:34 PM
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QUOTE(914sgofast2 @ Nov 22 2023, 04:12 PM) *

Are you hearing the fuel pump's initial pumping sound to prime the injectors with gas, before the engine even fires up? If so, that is normal.


Yes. The knocking occurs just before or perhaps during initial combustion on the passenger side. Maybe these are the last cylinders to get spark? Does start-up always use the same firing order?
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GregAmy
post Nov 22 2023, 08:58 PM
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I am hell-bent on this topic, so not objective...check the torque of the bolt holding the fan hub to the crank. 23 ft-lbs (though I'm thinking Blue Loc-tite and 30 ft-lbs...)
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930cabman
post Nov 23 2023, 07:11 AM
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QUOTE(GregAmy @ Nov 22 2023, 08:58 PM) *

I am hell-bent on this topic, so not objective...check the torque of the bolt holding the fan hub to the crank. 23 ft-lbs (though I'm thinking Blue Loc-tite and 30 ft-lbs...)


Not just the torque, but more importantly the fit between the fan hub and crank.
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GregAmy
post Nov 23 2023, 07:15 AM
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QUOTE(930cabman @ Nov 23 2023, 08:11 AM) *

Not just the torque, but more importantly the fit between the fan hub and crank.

(IMG:style_emoticons/default/agree.gif)

And if it's loose in any way, please stop driving it and remove the fan and hub and inspect the crank; you may already have damage.

http://www.914world.com/bbs2/index.php?showtopic=367703
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Superhawk996
post Nov 23 2023, 10:31 AM
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QUOTE(GregAmy @ Nov 22 2023, 10:58 PM) *

I am hell-bent on this topic, so not objective...

@gregamy

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I commend you on the self awareness

When I first read this thread my thought was that the description is vague enough to be virtually anything.

I love that you recognize you now have a hammer and everything looks like a nail. (IMG:style_emoticons/default/aktion035.gif)

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930cabman
post Nov 23 2023, 11:56 AM
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"everything looks like a nail"

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GregAmy
post Nov 23 2023, 12:14 PM
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(IMG:style_emoticons/default/drunk.gif)

Yup. But then again, I had that same noise, same time, same symptom -- and I ignored it, "could be anything"...

Now every noise is that problem. (IMG:style_emoticons/default/av-943.gif)
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Shivers
post Nov 23 2023, 01:46 PM
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Any idea how many miles on it. Worn P&C’s and also bearings can cause a knock.
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914sgofast2
post Nov 23 2023, 02:02 PM
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QUOTE(windforfun @ Nov 22 2023, 04:34 PM) *

QUOTE(914sgofast2 @ Nov 22 2023, 04:12 PM) *

Are you hearing the fuel pump's initial pumping sound to prime the injectors with gas, before the engine even fires up? If so, that is normal.


Yes. The knocking occurs just before or perhaps during initial combustion on the passenger side. Maybe these are the last cylinders to get spark? Does start-up always use the same firing order?

You hear the fuel pump noise from the passenger side because that’s where the fuel pump is located.
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windforfun
post Nov 23 2023, 07:59 PM
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Does start-up always use the same firing order?

All is tight. New belt & snug pulleys. 48K miles.

This has nothing to do with the fuel pump IMHO.

Happy Thanksgiving.
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Superhawk996
post Nov 23 2023, 08:09 PM
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QUOTE(windforfun @ Nov 23 2023, 09:59 PM) *

Does start-up always use the same firing order?

This has nothing to do with the fuel pump.

Happy Thanksgiving.

Firing order is fixed by engine design

1-4-3-2 for T4 engine

Never varies
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Superhawk996
post Nov 23 2023, 08:20 PM
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Video is going to be your best bet to get some real help rather than speculation.

There are so many things it could be.

I’ll give you a speculation:

Could it be timing? If your static timing is just a little bit too advanced? As engine is cranking slowly - sometimes you can get an ignition event too early in the compression stroke. It will sound somewhat like a rod knock. But then the engine catches on subsequent cylinders, rpm’s increase and then the advance is more appropriate to engine speed and the knock sound disappears.

When static timing is way too far advanced, you will get an outright cranking stoppage - stall of the engine because the ignition event happens so far before TDC it just stops the upward piston travel in its tracks. Usually with a clunk / knock / stall sound. This clearly isn’t happening in your case but there is a continuum between seamless starting and this worst case no-start & clunk/knock scenario.

Problem is we don’t know if this is what is happening on your car or if I’m just pulling this out of my (IMG:style_emoticons/default/bootyshake.gif)

Having someone crank - start while probing the engine with a mechanics stethoscope would go a long way toward narrowing down what you’re hearing or where it’s coming from.
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Superhawk996
post Nov 23 2023, 08:21 PM
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QUOTE(Root_Werks @ Nov 22 2023, 07:49 PM) *

See if you can get a video of start up for us.


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