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SmokinVette.com Forums : Corvette Forums : C4 Corvette Forums : C4 Tech & Performance : Sound found
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Old 03-04-2012, 07:58 AM   #1
Marv02
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Default Sound found

I was chasing a knocking sound in my Vett for a while now it’s been tracked down to the Fuel Pump Regulator.

It holds 43 PSI of pressure at Idle But as soon as you turn the engine off it drops to Zero.

It has almost NEW FIC Bosch III 24# injectors and same for the Fuel pump a Walberg 190.

When doing some more reading some are saying the Fuel pump regulator pulse dampener is bad.

That’s fine I ordered one where is it on the car.
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383 4 bolt main (10.5 to 1) Balanced, Flat top , pistons LT-4 Hotcam, C C ultra pro magnum steel 1.6 RRA, Trick Flow Heads Super 23 (195 runners) 62cc , SPL runners, Hi Flow intake base, 24# FIC Bosch 3 Injectors, Chipped, Melrose full headers, 3 way Main cat, Borla 11134.

700r4 Trans built, 2500 Stall Lock up Convertor, 307 rearend.

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Old 03-04-2012, 03:49 PM   #2
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Quote:
Originally Posted by Marv02 View Post
I was chasing a knocking sound in my Vett for a while now it’s been tracked down to the Fuel Pump Regulator.

It holds 43 PSI of pressure at Idle But as soon as you turn the engine off it drops to Zero.

It has almost NEW FIC Bosch III 24# injectors and same for the Fuel pump a Walberg 190.

When doing some more reading some are saying the Fuel pump regulator pulse dampener is bad.

That’s fine I ordered one where is it on the car.

Not knowing for sure I would guess it would be in the regulator. Like a spring-loaded diaphragm that smooths out the pulses from the fuel pump. Did you actually listen closely to the regulator? Are you absolutely sure that's where the tapping noise is coming from?
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Old 03-04-2012, 05:00 PM   #3
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Youn hear pluse from there.

Quote:
Originally Posted by toobroketoretire View Post
Not knowing for sure I would guess it would be in the regulator. Like a spring-loaded diaphragm that smooths out the pulses from the fuel pump. Did you actually listen closely to the regulator? Are you absolutely sure that's where the tapping noise is coming from?
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383 4 bolt main (10.5 to 1) Balanced, Flat top , pistons LT-4 Hotcam, C C ultra pro magnum steel 1.6 RRA, Trick Flow Heads Super 23 (195 runners) 62cc , SPL runners, Hi Flow intake base, 24# FIC Bosch 3 Injectors, Chipped, Melrose full headers, 3 way Main cat, Borla 11134.

700r4 Trans built, 2500 Stall Lock up Convertor, 307 rearend.

403 H/P @ 5000
498 TQ @ 3000
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Old 03-05-2012, 06:39 AM   #4
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You can hear pulse from there.

Well, hopefully that's it. Much better than hearing a LOUD knocking coming from the bottom end, huh?
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Old 03-09-2012, 04:37 PM   #5
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When I got home from work today my new pulse dampener was at the door

It took about 30 minutes to install it fired the car back up Idove it to work today it seems much better.

I find out more after the car sits and I can start it cold thats when it made the noise the worse.

But so far so good.
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383 4 bolt main (10.5 to 1) Balanced, Flat top , pistons LT-4 Hotcam, C C ultra pro magnum steel 1.6 RRA, Trick Flow Heads Super 23 (195 runners) 62cc , SPL runners, Hi Flow intake base, 24# FIC Bosch 3 Injectors, Chipped, Melrose full headers, 3 way Main cat, Borla 11134.

700r4 Trans built, 2500 Stall Lock up Convertor, 307 rearend.

403 H/P @ 5000
498 TQ @ 3000

Last edited by Marv02; 03-09-2012 at 04:46 PM.
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Old 03-10-2012, 06:55 AM   #6
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Did a cold start up this morning much much bettter there still a little noise but unles you were purpose listening for it you never notice it.

I going to order a new FPR diaphragm and see if this will completely get rid of all fuel rail noise.
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383 4 bolt main (10.5 to 1) Balanced, Flat top , pistons LT-4 Hotcam, C C ultra pro magnum steel 1.6 RRA, Trick Flow Heads Super 23 (195 runners) 62cc , SPL runners, Hi Flow intake base, 24# FIC Bosch 3 Injectors, Chipped, Melrose full headers, 3 way Main cat, Borla 11134.

700r4 Trans built, 2500 Stall Lock up Convertor, 307 rearend.

403 H/P @ 5000
498 TQ @ 3000
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Old 03-17-2012, 09:37 AM   #7
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The noise is back.

I am going to delete the 9th injector and see if this helps like I said before it only makes the noise when it is cold start up.
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383 4 bolt main (10.5 to 1) Balanced, Flat top , pistons LT-4 Hotcam, C C ultra pro magnum steel 1.6 RRA, Trick Flow Heads Super 23 (195 runners) 62cc , SPL runners, Hi Flow intake base, 24# FIC Bosch 3 Injectors, Chipped, Melrose full headers, 3 way Main cat, Borla 11134.

700r4 Trans built, 2500 Stall Lock up Convertor, 307 rearend.

403 H/P @ 5000
498 TQ @ 3000
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Old 03-17-2012, 11:06 AM   #8
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Originally Posted by Marv02 View Post
The noise is back.

I am going to delete the 9th injector and see if this helps like I said before it only makes the noise when it is cold start up.

Marv, be sure to check the inside of your distributor cap for signs of the rotor is hitting it as mine only made the "tapping" noise when it was cold too. Pull your cap and look right under the #5 terminal as that terminal is directly above the notch in the distributor housing.

After studying the problem I found the aftermarket caps have a slightly taller "indexing peg" than the A/C Delco caps have so the aftermarket caps don't sit down completely flat on the distributor housing.

And have you tried using a 1/2" to 5/8" diameter hose yet? A large hose will quickly find the source or ANY noise no matter how slight it is.
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Old 03-17-2012, 11:35 AM   #9
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I pulled the cap NO hitting at all the rotor seen better days I change that

I also pulled the distributor out and checked the end play it's at .017.

The Composite distributor gear is showing wear about half the teeth are worn though already with 7000 miles on it sounds funny to me also the upper 3/4 of the gear is worn more towarded the top of the gear.

I using the stock 1986 distributor with a composite gear is this my issues.

Quote:
Originally Posted by toobroketoretire View Post
Marv, be sure to check the inside of your distributor cap for signs of the rotor is hitting it as mine only made the "tapping" noise when it was cold too. Pull your cap and look right under the #5 terminal as that terminal is directly above the notch in the distributor housing.

After studying the problem I found the aftermarket caps have a slightly taller "indexing peg" than the A/C Delco caps have so the aftermarket caps don't sit down completely flat on the distributor housing.

And have you tried using a 1/2" to 5/8" diameter hose yet? A large hose will quickly find the source or ANY noise no matter how slight it is.
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383 4 bolt main (10.5 to 1) Balanced, Flat top , pistons LT-4 Hotcam, C C ultra pro magnum steel 1.6 RRA, Trick Flow Heads Super 23 (195 runners) 62cc , SPL runners, Hi Flow intake base, 24# FIC Bosch 3 Injectors, Chipped, Melrose full headers, 3 way Main cat, Borla 11134.

700r4 Trans built, 2500 Stall Lock up Convertor, 307 rearend.

403 H/P @ 5000
498 TQ @ 3000
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Old 03-17-2012, 11:38 AM   #10
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I used the rubber hose trick.
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383 4 bolt main (10.5 to 1) Balanced, Flat top , pistons LT-4 Hotcam, C C ultra pro magnum steel 1.6 RRA, Trick Flow Heads Super 23 (195 runners) 62cc , SPL runners, Hi Flow intake base, 24# FIC Bosch 3 Injectors, Chipped, Melrose full headers, 3 way Main cat, Borla 11134.

700r4 Trans built, 2500 Stall Lock up Convertor, 307 rearend.

403 H/P @ 5000
498 TQ @ 3000
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