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C5 FUEL PUMP "HUM"

 
mwctexas
I love my Chevy Chevette!
Posts: 2
Joined: 10/07
Posted: 05/05/08 11:43 AM

HELLO....
I'd appreciate information if you can offer some insight...
....i own a 2003 with 25,000 miles.....i bought it used at around 22,000 miles...i noticed a hum coming from the fuel pump...granted it was not a loud noise..but an annoying hum audible at slow speeds or in park...
...i asked 2 vette mechanics for opinions...one said he could replace the pump with a new one and it will probably make the same "noise"...the second mechanic said a new one would probably clear it up...although he didn't think the one in the car was about to crap out..
...oh well....several hundered dollars later and a new pump installed...it sounds almost like the old one....after a long drive...it gets a little louder...i feel like it is in fact perfectly normal.....but since i don't know any other c5 owners i'm hoping to learn from here....does yours hum?..
....thanks for reading this and have a good one....Mike  

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twoglides
I love my Chevy Chevette!
Posts: 2
Joined: 07/08
Posted: 07/22/08 02:26 PM

Yes mine and my wifes BOTH do.Most C-5 vettes do to.Just the way it is  

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tombenford
I love my Chevy Chevette!
Posts: 10
Joined: 07/08
Posted: 07/29/08 02:30 AM

Fuel pump noise in C5s is not an uncommon problem. This stems from the fact that there are two fuel tanks and, consequently, two fuel pumps. One of the pumps constantly pumps fuel from the passenger-side tank into the driver-side tank, and this pump is very quiet. The noisy one (and the one you hear) is the main fuel pump located behind the driver seat that feeds gas to the engine. Unfortunately, this pump can be loud enough to be quite annoying, but there is a 'quasi-cure' that involves adding a foam fuel tank insulator pad (GM part number 12493728) and the installation procedure is outlined in Chevrolet Service Bulletin number 99-06-04-052. Your other option is to have a quieter after-market pump installed, and these are available from several sources.   Hope this helps you out.
Tom Benford
Corvette Fever
C5/C6 Solutions Columnist  

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reb019047
I love my Chevy Chevette!
Posts: 4
Joined: 02/10
Posted: 02/20/10 10:22 PM

I own a 99 Vette, my fuel pump started huming at or below a half tank of fuel. I had the fuel pump replace with a brand new one from GM. It's doing it too. I have come up with an idea that may stop that annoying humming. I am going to replace the gas cap, yep the gas cap. So, think about it, all gas caps on any car are suppose to vent. Therefore if mine is clogged, then the fuel pump will be straining to pump fuel, therefore causing it to hum. What do you think. I am going to replace mine and see if this will stop it, cheap investment if it works.  

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reb019047
I love my Chevy Chevette!
Posts: 4
Joined: 02/10
Posted: 03/07/10 12:11 PM

Here I am again, since no one responded to my thread, here is what I did. Instead of buying a gas cap, I waited until it reach a half tank of fuel, where it begins to hum. I removed the gas cap and screwed it back on again. Cranked up my vette and realized there was no more humming. Maybe there is something to the gas cap theory after all. Or maybe it was just a fluke. I'm going to try it again.  

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waynep7122
I mow my lawn and find Chevys
Posts: 1114
Joined: 08/09
Posted: 03/07/10 07:57 PM

i would  check the vapor recovery system...     that system is supposed to control the fuel tank pressures...

it has a very sensitive pressure sensor in the top of the tank..


most smog shops will have a fuel cap tester... many states have the tester right on the smog machine..

most of the time.. as i understand.. the fuel caps will allow air in.. but not out..

if the vapor recovery system has failed.. it can cause vacuum in the tank... and really drive you crazy...

i understand about vacuum in a fuel tank..  that happened on a boat i worked on for many years..  the day tank in the engine room was full to the TOP...  the vent was closed... i tried to tell the owner/captain.. that the vent was closed.. but he knew what he was doing..    about 5 minutes away from the dock.. we lost the generator.. then the left motor .. then the right..  104' wooden boat in a  200' wide channel with concrete boulders for walls..   we dropped anchor to stop... took 2 hours to change the filters and get all three motors restarted..  if we had cleared the channel i was going to go below and open the valve..  the harbor patrol was way upset that we dropped anchor there..  and that we could not pull the 600 pound anchor up... by hand..    its been almost 10 years since that happened.. the boat actually sunk at anchor in santa barbara..  while i was out of town..  the owner was on it when it went down..   he floated .. the boat did not.  

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reb019047
I love my Chevy Chevette!
Posts: 4
Joined: 02/10
Posted: 03/15/10 11:56 AM

I am grateful for the reply. Didn't know that there was such a sensor on top of the tank. The main tank behind the drivers seat, right? I will look into it, thanks.  

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waynep7122
I mow my lawn and find Chevys
Posts: 1114
Joined: 08/09
Posted: 03/15/10 07:52 PM

here is a clipping from the autozone free repair info site...

EVAP Canister Purge & Vent Solenoids

Removal & Installation
Purge Solenoid Valve
5.7L & 6.0L V8 Engine
Remove the left fuel rail cover, if equipped.

Disconnect the engine vacuum pipe from the EVAP canister purge solenoid valve to intake manifold EVAP pipe.

Disconnect the engine purge pipe from the EVAP canister purge valve.

Disconnect the EVAP canister purge valve harness connector.

Remove the EVAP canister purge valve from the purge bracket.


To install:

Install the EVAP canister purge valve to the purge bracket.

Connect the harness connector to the EVAP canister purge valve.

Connect the engine purge pipe to the chassis purge pipe.

Connect the engine vacuum pipe to the EVAP canister purge valve.

Install the left fuel rail cover.


Vent Solenoid Valve
5.7L & 6.0L V8 Engines
Raise the vehicle.

Lower the right muffler for automatic transmission equipped vehicles only.

Disconnect the EVAP canister valve harness connector.

Disconnect the vent hose (2) from the EVAP canister vent valve (1). See illustration above.

Remove the EVAP canister vent valve from the vent bracket.


To install:

Install the EVAP canister vent valve to the vent bracket.

Connect the vent hose (2) to the EVAP canister vent valve (1).

Connect the EVAP vent valve electrical connector.

For automatic transmission- equipped vehicles only, raise the right muffler.

Lower the vehicle.


Testing
The EVAP control system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent line and the EVAP vent solenoid to the atmosphere. The EVAP canister stores the fuel vapors until the engine is able to use the vapors. At an appropriate time, the PCM will command the EVAP purge valve open, allowing engine vacuum to be applied to the EVAP canister. With the EVAP vent valve open, fresh air will be drawn through the valve and vent line to the EVAP canister. Fresh air is drawn through the canister, pulling fuel vapors from the carbon. The air/fuel vapor mixture continues through the EVAP purge pipe and EVAP purge valve into the intake manifold to be consumed during normal combustion. The EVAP system requires the PCM be able to detect a leak as small as 1 mm (0.040 inch) in the EVAP system. The PCM uses several tests to determine if the EVAP system is sealed.

Canister Vent Restriction Test
If the EVAP vent system is restricted, fuel vapors will not be properly purged from the EVAP canister. The PCM tests this condition by commanding the EVAP purge valve CLOSED and commanding the EVAP vent valve OPEN and monitoring the FTP sensor for an increase in vacuum. If an increase in vacuum is detected, DTC P0446 will set.

EVAP Service Bay Test
The EVAP service bay test is accessed with a scan tool, and allows EVAP diagnostic tests to be run at higher engine coolant temperatures (ECT) than are allowed during normal testing. The EVAP service bay test allows all of the above tests to be run on demand. When the EVAP service bay tests are run, the scan tool will indicate that the tests have passed, or will indicate which specific DTC has failed. If a EVAP service bay test fails, DTCs will not be recorded in the PCM Freeze Frame/Failure Records. The DTCs will only be displayed on the scan tool. The EVAP service bay test is useful in determining if a fault is present, and for verifying a repair.

The EVAP purge valve controls the flow of vapors from the EVAP system to the intake manifold. This normally closed valve is pulse width modulated by the PCM in order to precisely control the flow of fuel vapor to the engine. The valve will also be opened during some portions of the EVAP testing, allowing engine vacuum to enter the EVAP system.



Fig.

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0996b43f/80/20/27/65/medium/0996b43f80202765.gif

The EVAP vent valve (1) controls the fresh airflow into the EVAP canister. The EVAP is a normally open valve. The PCM will command the valve closed during some EVAP tests, allowing the system to be tested for leaks



Fig. Location of EVAP vent solenoid valve (1) on Corvette 5.7L & 6.0L V8 engines
copy and paste this link to see the picture
http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0996b43f/80/20/27/66/medium/0996b43f80202766.gif



Purge Valve Leak Test
If the EVAP purge valve does not seal properly, fuel vapors could enter the engine at an undesired time, causing driveability concerns. The PCM tests for this condition by commanding the EVAP purge and vent valves closed, sealing the system, and monitoring the FTP for an increase in vacuum. If the PCM detects an increase in vacuum, DTC P1441 will set.

Vacuum Decay Test
If the weak vacuum test passes, the PCM will command OFF the EVAP purge valve, sealing the EVAP system. The PCM tests for vacuum decay in the EVAP system by monitoring the FTP sensor for a change in voltage over a period of time. If the decay rate is more than a calibrated value, the PCM will rerun the test. If the test fails again, a DTC P0442 will set.

Weak Vacuum Test
This tests for large leaks and blockages in the EVAP system. The PCM will command ON and close the EVAP vent valve and will command ON and open the EVAP purge valve with the engine running, allowing engine vacuum into the EVAP system. The PCM monitors the FTP sensor in order to verify that the system is able to reach a predetermined level of vacuum within a set amount of time. If the PCM does not detect the predetermined vacuum level on 2 consecutive tests, a DTC P0440 will set.


you can copy and paste this into an email to make the links clickable...

let me know what happens..

you are also going to need a scan tool...

a harbor freight 98614 will work...  the other cheeper ones don't show live data..  its neat being able to view live data from the ECM..  sure makes cars easy to fix also...  

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1970-13
I love my Chevy Chevette!
Posts: 1
Joined: 03/12
Posted: 03/11/12 11:13 AM

c-5"s have two fuel pumps,the one that we can all hear the most is behind the drivers seat; the earlier models could be heard the most, later models were added more sound suppresion but you. It reduce the noise but it's always going to be there.  

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pepsi1
V-6 Camaros rule!
Posts: 83
Joined: 01/12
Posted: 03/11/12 11:07 PM

Here's what I did with my brothers 2002 ZO6. I pulled the pump out and reisulated the whole pump. Then when I reinstalled it I made sure I insulated the mounting bracket, the out side hoses as far as I could reach them. Then installed a larger return line.

Now you can't hear a buzz a hum. You can hear the fuel pump relay click but that's it.

We took it to  the club he belongs to in Florida. We went and ran the car at Daytona set it up as GM says I was driving the first time. I got it up to a 168MPH and it felt great. The second time I set the set the camber more positive. I went 171MPH.

I can't believe the guys that buy  Hi-Performance cars and they have the chance to step on it and they don't. There were two other guys that had them going 157 MPH 138MPH. My brother only went 130MPH it was a fun day. There was a Porche club there to but they ran the inner loop.

So as far as I know the pump is still quiet. Watch where the fuel lines touch the chassis or any other part of the under carriage. The lines on the return side I believe is where the problem is part of did you ever feel the return line, on his 2002 if you touched it you could get the vibration or humm. The dealer wanted to know what he did to quiet it. They have a ton of complaints.........

Thanks, Bob  

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crasnak
I love my Chevy Chevette!
Posts: 1
Joined: 08/12
Posted: 08/01/12 07:35 AM

I also have a 99 vette I bought with 17k miles.  It now has 164k miles.  I was driving in the mountains one day a couple years ago and the fuel pump began to whine very loudly, I took the cap off and gas sprayed out about 20 feet, then I put the cap back on and it stopped.  A few days later the same thing happened again, so I put a new cap on and it hasn't done it again since.  

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