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The Following brands are available based on your search.

  • Cardone
    Cardone
  • Dorman
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    Standard Ignition

Best Selling Genuine Gmc Vacuum Pumps

  • We Stock the following top leading brands, including Cardone, Dorman, Standard Ignition
  • Constantly Updated Inventory of Gmc Replacement Vacuum Pump Parts
Cardone
1998 GMC B7 Vacuum Pump 8 Cyl 6.5L Cardone

P311-18E650B    64-1025  Remanufactured

Qty:
$5.40 $72.35
Cardone Vacuum Pump
  • Vacuum Pump - Domestic
  • Reman. A-1 CARDONE Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: Remanufactured
    • Pulley Included: No
  • A1 CARDONE Remanufactured Vacuum Pumps are engineered for quick installation and no comebacks. Each unit is engineered and tested to meet or exceed Original Equipment Manufacturer performance, providing you reliable performance, every time. Original design weaknesses are corrected to make a longer lasting part you and your vehicle can rely on.
Brand: Cardone
Additional Fitment Information:
Vehicle Block CC CID Fuel Type
1998 - GMC B7 V - 395 DIESEL
Cardone
1997 GMC C1500 Vacuum Pump 8 Cyl 6.5L Cardone

P311-5E61E2E    64-1018  Remanufactured

Qty:
$5.40 $72.35
Cardone Vacuum Pump
  • Vacuum Pump - Domestic
  • Reman. A-1 CARDONE Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: Remanufactured
    • Pulley Included: No
  • A1 CARDONE Remanufactured Vacuum Pumps are engineered for quick installation and no comebacks. Each unit is engineered and tested to meet or exceed Original Equipment Manufacturer performance, providing you reliable performance, every time. Original design weaknesses are corrected to make a longer lasting part you and your vehicle can rely on.
Brand: Cardone
Additional Fitment Information:
Vehicle Block CC CID Fuel Type
1997 - GMC C1500 V - 395 DIESEL
Cardone
1993 GMC C1500 Vacuum Pump 8 Cyl 6.2L Cardone

P311-311955C    64-1009  Remanufactured

Qty:
$5.40 $72.35
Cardone Vacuum Pump
  • Vacuum Pump - Domestic
  • Reman. A-1 CARDONE Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: Remanufactured
    • Pulley Included: No
  • A1 CARDONE Remanufactured Vacuum Pumps are engineered for quick installation and no comebacks. Each unit is engineered and tested to meet or exceed Original Equipment Manufacturer performance, providing you reliable performance, every time. Original design weaknesses are corrected to make a longer lasting part you and your vehicle can rely on.
Brand: Cardone
Additional Fitment Information:
Vehicle Block CC CID Fuel Type
1993 - GMC C1500 V - 379 DIESEL
Dorman
1997 GMC C1500 Vacuum Pump - N/A 8 Cyl 6.5L Dorman

P311-4DB9592    904-801  New

Qty:
$104.33
Dorman Vacuum Pump  N/A
  • Product Attributes:
    • Feature - Benefit 1: Direct Replacement For Ease Of Installation
    • Feature - Benefit 2: Re-engineered Radial Ball Bearing Provides A Greater Load Capacity For Improved Durability
    • Feature - Benefit 3: Mechanical And Electric Vacuum Pumps Available
    • Feature - Benefit 4: No Core Return Hassles
    • Gasket or Seal Included: No
    • Housing Material: Metal
    • Item Grade: Standard Replacement
    • Package Contents: Pump Assembly
    • Pulley Included: No
    • Vacuum Pump Connector: Barbed
    • Vacuum Pump Drive System: Belt Drive
    • Vacuum Pump Inlet: 3/8 In.
    • Vacuum Pump Outlet: 3/8 In.
    • Vacuum Relief Valve: Yes
Brand: Dorman
Additional Fitment Information:
Vehicle Block CC CID Position
1997 - GMC C1500 V - 395 N/A
Dorman
1997 GMC C1500 Vacuum Pump - N/A 8 Cyl 6.5L Dorman

P311-4DB9592    904-801  New

Qty:
$104.33
  • Product Attributes:
    • Gasket or Seal Included: No
    • Housing Material: Metal
    • Item Grade: Standard Replacement
    • Package Contents: Pump Assembly
    • Pulley Included: No
    • Vacuum Pump Connector: Barbed
    • Vacuum Pump Drive System: Belt Drive
    • Vacuum Pump Inlet: 3/8 In.
    • Vacuum Pump Outlet: 3/8 In.
    • Vacuum Relief Valve: Yes
Brand: Dorman
Additional Fitment Information:
Vehicle Block CC CID Position
1997 - GMC C1500 V - 395 N/A
Cardone
1998 GMC B7 Vacuum Pump 8 Cyl 6.5L Cardone

P311-064D19D    90-1025  New

Qty:
$109.24
Cardone Vacuum Pump
  • Vacuum Pump - Domestic New
  • New CARDONE Select Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: New
    • Pulley Included: No
  • CARDONE Select New Vacuum Pumps are backed by CARDONE Select Engineered (CSE) Technology, which ensures that all CARDONE Select New Vacuum Pumps meet or exceed O.E. form, fit and function. CSE Technology is based on over 40 years of reverse-engineering expertise, where original design weaknesses are identified and corrected, resulting in premium-quality, brand-new parts you can rely on. All units adhere to strict S.A.E. specifications and are 100% tested to ensure reliable, long-lasting performance.
Brand: Cardone
Additional Fitment Information:
Vehicle Block CC CID Fuel Type
1998 - GMC B7 V - 395 DIESEL
Cardone
1993 GMC G2500 Vacuum Pump 8 Cyl 6.2L Cardone

P311-5F34F72    64-1023  Remanufactured

Qty:
$5.40 $72.35
Cardone Vacuum Pump
  • Vacuum Pump - Domestic
  • Reman. A-1 CARDONE Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: Remanufactured
    • Pulley Included: No
  • A1 CARDONE Remanufactured Vacuum Pumps are engineered for quick installation and no comebacks. Each unit is engineered and tested to meet or exceed Original Equipment Manufacturer performance, providing you reliable performance, every time. Original design weaknesses are corrected to make a longer lasting part you and your vehicle can rely on.
Brand: Cardone
Additional Fitment Information:
Vehicle Block CC CID Fuel Type
1993 - GMC G2500 V - 379 DIESEL
Cardone
1997 GMC C1500 Vacuum Pump Cardone

P311-480203D    90-1018  New

Qty:
$109.24
Cardone Vacuum Pump
  • Vacuum Pump - Domestic New
  • New CARDONE Select Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: New
    • Pulley Included: No
  • CARDONE Select New Vacuum Pumps are backed by CARDONE Select Engineered (CSE) Technology, which ensures that all CARDONE Select New Vacuum Pumps meet or exceed O.E. form, fit and function. CSE Technology is based on over 40 years of reverse-engineering expertise, where original design weaknesses are identified and corrected, resulting in premium-quality, brand-new parts you can rely on. All units adhere to strict S.A.E. specifications and are 100% tested to ensure reliable, long-lasting performance.
Brand: Cardone
Additional Fitment Information:
Vehicle Fuel Type
1997 - GMC C1500 DIESEL
Cardone
1993 GMC C1500 Vacuum Pump 8 Cyl 6.2L Cardone

P311-1D8D76B    64-1005  Remanufactured

Qty:
$15.30 $70.72
Cardone Vacuum Pump
  • Vacuum Pump - Domestic
  • Reman. A-1 CARDONE Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: Remanufactured
    • Pulley Included: No
  • A1 CARDONE Remanufactured Vacuum Pumps are engineered for quick installation and no comebacks. Each unit is engineered and tested to meet or exceed Original Equipment Manufacturer performance, providing you reliable performance, every time. Original design weaknesses are corrected to make a longer lasting part you and your vehicle can rely on.
Brand: Cardone
Additional Fitment Information:
Vehicle Block CC CID Fuel Type
1993 - GMC C1500 V - 379 DIESEL
Cardone
1995 GMC C1500 Vacuum Pump Cardone

P311-2C1ABF4    90-1009  New

Qty:
$109.24
Cardone Vacuum Pump
  • Vacuum Pump - Domestic New
  • New CARDONE Select Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: New
    • Pulley Included: No
  • CARDONE Select New Vacuum Pumps are backed by CARDONE Select Engineered (CSE) Technology, which ensures that all CARDONE Select New Vacuum Pumps meet or exceed O.E. form, fit and function. CSE Technology is based on over 40 years of reverse-engineering expertise, where original design weaknesses are identified and corrected, resulting in premium-quality, brand-new parts you can rely on. All units adhere to strict S.A.E. specifications and are 100% tested to ensure reliable, long-lasting performance.
Brand: Cardone
Additional Fitment Information:
Vehicle Fuel Type
1995 - GMC C1500 DIESEL
Cardone
1995 GMC C1500 Vacuum Pump Cardone

P311-306A491    90-1005  New

Qty:
$100.63
Cardone Vacuum Pump
  • Vacuum Pump - Domestic New
  • New CARDONE Select Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: New
    • Pulley Included: No
  • CARDONE Select New Vacuum Pumps are backed by CARDONE Select Engineered (CSE) Technology, which ensures that all CARDONE Select New Vacuum Pumps meet or exceed O.E. form, fit and function. CSE Technology is based on over 40 years of reverse-engineering expertise, where original design weaknesses are identified and corrected, resulting in premium-quality, brand-new parts you can rely on. All units adhere to strict S.A.E. specifications and are 100% tested to ensure reliable, long-lasting performance.
Brand: Cardone
Additional Fitment Information:
Vehicle Fuel Type
1995 - GMC C1500 DIESEL
Cardone
1993 GMC G2500 Vacuum Pump Cardone

P311-51ACA1D    90-1023  New

Qty:
$98.78
Cardone Vacuum Pump
  • Vacuum Pump - Domestic New
  • New CARDONE Select Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: New
    • Pulley Included: No
  • CARDONE Select New Vacuum Pumps are backed by CARDONE Select Engineered (CSE) Technology, which ensures that all CARDONE Select New Vacuum Pumps meet or exceed O.E. form, fit and function. CSE Technology is based on over 40 years of reverse-engineering expertise, where original design weaknesses are identified and corrected, resulting in premium-quality, brand-new parts you can rely on. All units adhere to strict S.A.E. specifications and are 100% tested to ensure reliable, long-lasting performance.
Brand: Cardone
Additional Fitment Information:
Vehicle Fuel Type
1993 - GMC G2500 DIESEL
Cardone
1990 GMC C6000 Vacuum Pump 8 Cyl 8.2L Cardone

P311-09CD8A7    64-1512  Remanufactured

Qty:
$5.40 $292.72
Cardone Vacuum Pump
  • Vacuum Pump - Domestic
  • Reman. A-1 CARDONE Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: Remanufactured
    • Pulley Included: No
  • A1 CARDONE Remanufactured Vacuum Pumps are engineered for quick installation and no comebacks. Each unit is engineered and tested to meet or exceed Original Equipment Manufacturer performance, providing you reliable performance, every time. Original design weaknesses are corrected to make a longer lasting part you and your vehicle can rely on.
Brand: Cardone
Additional Fitment Information:
Vehicle Block CC CID
1990 - GMC C6000 V - 501
Dorman
1988 GMC C1500 Vacuum Pump - N/A 8 Cyl 6.2L Dorman

P311-303988F    904-803  New

Qty:
$93.93
Dorman Vacuum Pump  N/A
  • wo/Air Conditioning
  • Product Attributes:
    • Feature - Benefit 1: Direct Replacement For Ease Of Installation
    • Feature - Benefit 2: Re-engineered Radial Ball Bearing Provides A Greater Load Capacity For Improved Durability
    • Feature - Benefit 3: Mechanical And Electric Vacuum Pumps Available
    • Feature - Benefit 4: No Core Return Hassles
    • Gasket or Seal Included: No
    • Housing Material: Metal
    • Item Grade: Standard Replacement
    • Package Contents: Pump Assembly
    • Pulley Included: No
    • Vacuum Pump Connector: Barbed
    • Vacuum Pump Drive System: Belt Drive
    • Vacuum Pump Inlet: 3/8 In.
    • Vacuum Pump Outlet: 3/8 In.
    • Vacuum Relief Valve: Yes
Brand: Dorman
Additional Fitment Information:
Vehicle Block CC CID Position
1988 - GMC C1500 V - 379 N/A
Dorman
1988 GMC C1500 Vacuum Pump - N/A 8 Cyl 6.2L Dorman

P311-303988F    904-803  New

Qty:
$93.93
  • wo/Air Conditioning
  • Product Attributes:
    • Gasket or Seal Included: No
    • Housing Material: Metal
    • Item Grade: Standard Replacement
    • Package Contents: Pump Assembly
    • Pulley Included: No
    • Vacuum Pump Connector: Barbed
    • Vacuum Pump Drive System: Belt Drive
    • Vacuum Pump Inlet: 3/8 In.
    • Vacuum Pump Outlet: 3/8 In.
    • Vacuum Relief Valve: Yes
Brand: Dorman
Additional Fitment Information:
Vehicle Block CC CID Position
1988 - GMC C1500 V - 379 N/A
Cardone
1981 GMC C1500 Vacuum Pump 8 Cyl 5.7L Cardone

P311-1BA4BC7    64-1200  Remanufactured

Qty:
$117.06
Cardone Vacuum Pump
  • Vacuum Pump - Domestic
  • Reman. A-1 CARDONE Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: O-ring, Instruction Sheet
    • Product Condition: Remanufactured
    • Pulley Included: No
  • A1 CARDONE Remanufactured Vacuum Pumps are engineered for quick installation and no comebacks. Each unit is engineered and tested to meet or exceed Original Equipment Manufacturer performance, providing you reliable performance, every time. Original design weaknesses are corrected to make a longer lasting part you and your vehicle can rely on.
Brand: Cardone
Additional Fitment Information:
Vehicle Block CC CID Fuel Type
1981 - GMC C1500 V - 350 DIESEL
Cardone
1985 GMC S15 Vacuum Pump 4 Cyl 2.2L Cardone

P311-3D0236F    64-1020  Remanufactured

Qty:
$18.90 $90.22
Cardone Vacuum Pump
  • Vacuum Pump - Domestic
  • Reman. A-1 CARDONE Vacuum Pump
  • Product Attributes:
    • Mounting Brackets Included: No
    • Package Contents: Instruction Sheet
    • Product Condition: Remanufactured
    • Pulley Included: No
  • A1 CARDONE Remanufactured Vacuum Pumps are engineered for quick installation and no comebacks. Each unit is engineered and tested to meet or exceed Original Equipment Manufacturer performance, providing you reliable performance, every time. Original design weaknesses are corrected to make a longer lasting part you and your vehicle can rely on.
Brand: Cardone
Additional Fitment Information:
Vehicle Block CC CID Fuel Type
1985 - GMC S15 L - 134 DIESEL
Dorman
1988 GMC C1500 Vacuum Pump - N/A 8 Cyl 6.2L Dorman

P311-35F0AD4    904-804  New

Qty:
$104.33
Dorman Vacuum Pump  N/A
  • w/Air Conditioning
  • Product Attributes:
    • Feature - Benefit 1: Direct Replacement For Ease Of Installation
    • Feature - Benefit 2: Re-engineered Radial Ball Bearing Provides A Greater Load Capacity For Improved Durability
    • Feature - Benefit 3: Mechanical And Electric Vacuum Pumps Available
    • Feature - Benefit 4: No Core Return Hassles
    • Gasket or Seal Included: No
    • Housing Material: Metal
    • Item Grade: Standard Replacement
    • Package Contents: Pump Assembly
    • Pulley Included: No
    • Vacuum Pump Connector: Barbed
    • Vacuum Pump Drive System: Belt Drive
    • Vacuum Pump Inlet: 3/8 In.
    • Vacuum Pump Outlet: 3/8 In.
    • Vacuum Relief Valve: Yes
Brand: Dorman
Additional Fitment Information:
Vehicle Block CC CID Position
1988 - GMC C1500 V - 379 N/A
Standard Ignition
1982 GMC K1500 Vacuum Pump Standard Ignition

P311-47EA02D    VCP108  New

Qty:
$137.37
Standard Ignition Vacuum Pump
  • Front of Engine
  • Vacuum Pump
Brand: Standard Ignition
Additional Fitment Information:
Vehicle Fuel Type
1982 - GMC K1500 DIESEL

Latest Gmc Repair and Vacuum Pump Installation Advice

CarJunky AutoAdvice

96 GMC Sierra 5.7 upper intake removal

Showing 2 out of 16 Posts | Show 14 Hidden Posts
Question From HKman on 96 GMC Sierra 5.7 upper intake removal

Tried to remove upper intake plenum on 96 GMC Sierra 5.7 to resolve OBD2 codes P0300 and P0175. Secondary spark test completed (passed). Fuel pressure test shows a rapid drop from 60 psi to 15 psi after turning off ignition. Need to get a look at the fuel pressure regulator, injectors, poppets, etc. The upper intake bolts are all removed. Intake plenum will shift from side to side and back and forth but hangs up (underneath?).

Response From Hammer Time

Have you removed the wire harness and fuel lines?

Response From HKman

Yes, along with other misc. parts (throttle linkage, coil, pcv valve, etc.).

Response From Hammer Time

You're just missing a bolt somewhere.

Response From HKman

I'm able to move it around about 1/4" or so in all directions. It raises up maybe about 1/8".

Response From Discretesignals

Then it is sticking to the injector assembly o ring. Hold the top of the injector down and pull up on the intake. It should pop off.

Response From HKman

Upper intake removal issue - status: RESOLVED.
Thanks, you nailed it.

Response From Hammer Time

How do to plan on identifying a problem now that you have it apart? I think you should have done a little more testing before disassembly.

Response From HKman

After I hook the fuel lines back up I'll have someone put the ignition switch in the on position to return pressure to the fuel system while I monitor the injector assembly for any signs of fuel leaking. Upon performing a fuel pressure drop test I observed a rapid psi reduction after turning off the ignition. (from 60 psi to around 15 psi within about 15 seconds). Am I chasing a ghost?

Response From Hammer Time

No, you're probably on the right track but there are other explanations for a fuel pressure drop and if you had looked at scan tool data first, you would have a much better idea what is happening. You would have looked at the short and long term adaptives and watched for them to immediately start trying to correct for the leaking fuel. It would also be a good idea to examine the 2 center plugs on the drivers side for excess fouling because that is where most of the fuel flows.

Response From HKman

Sorry, I left that part out. My scan data reading for the long term fuel trim was stagnant at minus 18 at both banks. In my mind that was hinting to a possible continuous extreme rich fuel condition. That falls in line with my p0175 diagnostic code that keeps showing up.

Response From Hammer Time

Let us know what you find.

Response From Discretesignals

Another thing is if regulator is leaking, you'll see a nice clean spot on the floor of the intake. The gas will clean the carbon off.

Response From Discretesignals Top Rated Answer

Just another thing that I remembered. Sometimes a regulator with a leaky diaphragm may not leak unless there is vacuum on it. You may have to hook up a clear hose to the regulator's nipple and use a hand held vacuum pump while the fuel pump is running.

Response From HKman

Replaced fuel pressure regulator. Bottom of intake was gunk free underneath FPR vacuum tube just like you said it would be if it was leaking. Fuel pressure test verified this was the case.

Response From Discretesignals

If you have the fuel pipes to the injector off and the bolts around the upper intake including the ones in the rear of the upper, then it is probably hanging onto the top of the injector assembly. There is an oval shaped o ring that the top of the injector slides through that likes to stick. Put your thumbs on top of the injector while pushing it down and lift up on the bottom of the intake manifold.

1995 K1500 Running Rough at Half Throttle

Showing 4 out of 28 Posts | Show 24 Hidden Posts
Question From MarineGrunt on 1995 K1500 Running Rough at Half Throttle

I haven't been around in awhile and hope everyone is doing well.


I have someone with a 1995 K1500 with the 5.7 with close to 200k on it. Here's the email I got from him.........
"It is a 95 GMC K1500 with the 5.7 (pre-Vortec) and almost 200,000 miles. The problem is with it running rough at part throttle, around 1200 rpm. Once you get through that at half throttle or more, it seems to be fine. I have given it a complete tune up, new fuel filter and new throttle body injectors with little to no change. I wonder about the catalytic converter because it is original. I would remove or replace it but is a single piece unit with the y pipe and y pipe bolts are completely rusted out. I would consider cutting off the converter and welding a different one on or just straight pipe but I don't have a welder capable of doing so."


I don't have the truck yet but will be getting it soon so didn't know if someone would have any ideas off of the top of their head or could point me in the right direction for troubleshooting so I can get started on it right away.


Thanks!

Response From Hammer Time

Hey stranger..........
by the way you missed your football picks again.


I would take a hard look at the EGR system. Make sure it's not sticking open or leaking into the intake somewhere.

Have the codes read and see if there are any clues there.

Response From MarineGrunt

Thanks for the starting point HT. I appreciate it. I'm sure I'll have plenty more questions once he brings the truck over.
Yeah, not sure if you remember but we moved back in April. I was busy with work and busy getting settled in. Now it's time to get back to doing some work on vehicles. I really enjoy it and have missed it. The attached two stall garage is 24X30 and has a 12' ceiling so I finally have some decent space. I'd still like to build an building out back in the future. I'd love to have a lift.
I got on last night right before the game and did my picks. I remembered at like 6:47 central time. I had better check though. Maybe I didn't save them.

Response From Hammer Time

Yep, you did save them. I hadn't been back since just before the game.

Response From kev2

this is a 1995 and you mention TBI - just the 2 injectors?

this is a easy to work system- BASICS.
fuel pressure - easier said than done BUT critical.
CODES - easy and quick- even if CEL is off.
Parts - AC Delco
For the cat concern- do you have a simple VACUUM gauge?

Response From Tom Greenleaf Top Rated Answer

Hi MG! My 2 cents - Not converter yet if only part throttle issues but that's when EGR does it's work so suspect that or isn't getting properly controlled.


Vacuum gauge: If you don't have one get a pistol type with hose, gauge and assorted taps to monitor vacuum and it is also a vacuum pump for checking integrity of vacuum controlled items and diaphragms too.


An exhaust restriction from any cause while watching a vacuum gauge first at idle and again with no load at say 2,000 RPMs should be the same or real close. That is taken from manifold actual vacuum but "T" in so anything else it runs to gets the vacuum as you just observe,


T

Response From Hammer Time

These symptoms do not indicate plugged exhaust.

Response From Tom Greenleaf

No they don't indicate an exhaust restriction. The pump and gauge mentioned can both watch and just show an item works at what vacuum like the EGR (system) highly suspect IMO,


T

Response From MarineGrunt

The guy just dropped off the truck Monday evening so going to start messing with it in the morning. Sounds like the first thing I should do is test the egr valve. I'll let you know what I find.
Thanks for the help!

Response From MarineGrunt

I hooked a vacuum pump up to the egr valve and it doesn't hold any pressure at all. That is the correct way to test it, right?

Response From Hammer Time

Yes, some require exhaust backpressure before they will open.

Response From Discretesignals

If it a positive back pressure valve, you have to stuff a rag into the tail pipe to create some back pressure while applying vacuum to the valve. With the engine running of course...LOL.

Hanging in there buddy. Good to see your back around this joint.

Response From MarineGrunt

I'd have to replace every exhaust pipe in order to create back pressure. Any other ideas or a way to tell if it's a positive backpressure valve or not? I guess I could pull it off and test it by rigging a way to plug it.

Response From MarineGrunt

You can see how I plugged it off in the picture below. I used a rubber cork in the opening with the plunger. My question here is, will that rubber cork prevent the plunger from moving thus not allowing the valve to close? If so, I figure I'll get a bigger rubber cork, hollow out the center, and put it on the outside.


The gauge instantly starts dropping, stops at 2 for about 3 seconds, and then drops to 0. It's doing the same thing when the egr valve is on the truck. I tested my vacuum pump and it seems to be working fine.

By the way, no codes were present or in the history. The battery looks brand new though so the history was probably wiped out when replaced.



Response From Hammer Time

No, you can't test a feedback EGR that way. It has to be done with the engine running. The exhaust pressure triggers a valve inside the EGR that seals up the vacuum and allows it to be pulled open.

What we are looking for in your case is a valve that either isn't closing all the way or is opening too early when you're driving. If the pintle looks fully seated, put it back on the truck and try running the truck with the vacuum hose removed and plugged and see if the symptoms go away.

Response From MarineGrunt

Okay....I just assumed there was a flapper inside that closed once I put vacuum to it. So you're saying if I leave the vacuum hose unplugged, and symptoms go away, I know it's the culprit?
One other thing that might be worth mentioning is when you start the truck it cranks 5 or so times before it turns over. I had a few vehicles in the past where the fuel pressure regulator fixed an issue like that. I didn't know if maybe that would be worth looking it into after I'm done messing with the egr?

Response From Hammer Time

That would prove the problem is in the EGR system, not necessarily the valve itself.

Response From kev2

install the valve.
be sure the pintel is seated.
with enging running remove the vacuum line from EGR valve follow it back to solenoid
is there VACUUM ? yes before solenoid (Sol to eng) no after solenoid. (sol to VAlve).

plug the vacuum line - drive vehicle - is it still having an isue?

Response From MarineGrunt

There is vacuum before the solenoid and no vacuum after.
Going to plug the line and take it for a drive.

Response From MarineGrunt

It runs fine with the egr unhooked. I'm thinking it's the egr and not the solenoid just because it does hold a vacuum, although barely at about 2 inches, for about 4 seconds. If it was a positive back pressure valve it wouldn't have a vacuum at all, correct? The line is getting vacuum on the engine side of the solenoid so I believe the lines are okay. Is there anything else besides the solenoid in the egr system? If the solenoid checks out, and the lines are okay, could it be anything else besides the valve?

Response From Hammer Time

The solenoid is a possibility too. It isn't just on and off. It gets a series of pulses. The bottom line is the valve is opening too soon and likely too much. Could be either one or even the ECM programming. That car is probably using a PROM.

Response From kev2

if you want to dive deeper into this - EGR disconnected - hook a vacuum gauge to the solenoid OUT and route the gauge so you can see as you drive- not as difficulrt as it sounds. BE AWARE that the windshield is there and its glass- as you drive observe the vacuum reading- should go to manifold @20" then return to 0 -

EGR seating is sometimes held OPEN by a piece of carbon.. ask a REAL parts store if there is a screened gasket for the EGR on this engine 5.7? If you replace the EGR do NOT get cheap avoid anything that comes with shims bushings...chevy wants the serial number to get correct one - yet advance has one that fits many engines wonder why?

with a mityvac- will the EGR valve open when vac applied or dump all vacuum as soon as it get pumped up? it should oen hold @30sec and bleed off

Response From MarineGrunt

It ended up being the valve. Truck seems to be running great. This was the first time I've ever had to mess with the egr system on any vehicle and you guys made it all easy to understand. I really appreciate all of the help!

Response From Discretesignals

It was pretty common on those valves for the spring inside to get worn out and change the way the valve opens. Seen that happen a lot on the Buick Roadmasters. You could duplicate by brake torquing the engine with light throttle. If the engine surged, usually the EGR valve was the culprit.

As for the delayed starting, cycle the key from on to off a few times before starting the engine. This primes the fuel system. If it starts up just fine after priming a few times, you might have a fuel pressure drain back problem. Connect a fuel pressure gauge and look for pressure bleed off after the pump turns off. If it does, you either have a bad check valve in the fuel pump, which is very common, or a leaking fuel pressure regulator. If the injectors were leaking, I'm sure you would have seen that by now.

Response From Hammer Time

AMAZING........... we solved one of MG's problems in only one page........................LOL


I hope this post doesn't start a second page now....LOL

Response From Tom Greenleaf

Hmmm? Some funky. One vacuum hose goes to this EGR? With it off now you might be able to just pull on diaphragm while off and cool with vacuum line plugged while retracted or with vac pump and it should stay close to where it is not move the pintle any more with your rig (you are a hoot) off of it.


I've only had marginal luck cleaning a leaking pintle pressing it against wood with carb cleaner but those that can't shut should have a lousy idle not so much this mid throttle issue when it should be working. Idea of EGR is off at idle and off again at WOT. Little older on some people would plug the whole thing off thinking it would help for power and doesn't but can make engine knock instead as it's counting on some exhaust gas to flow back thru the thing to lower temp of combustion in turn reduces CO emissions and emissions in general but not harm performance,


T

Response From Discretesignals

pressure? Should hold vacuum unless it has a torn diaphram, your vacuum pump leaks, or it is one of those positive backpressure EGR valves.

Response From MarineGrunt

Hey DS...how have things been going?
I checked my pump and it's good to go. How do I know if it's a positive backpressure valves?



GMC 4.3 won't idle clears up at 3000 RPM

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Question From giddyuperic on GMC 4.3 won't idle clears up at 3000 RPM

Hello I have a 1995 4.3 liter engine ran fine for years and ran fine Friday and then parked it next day won't idle but runs fine over 3000 RPM and it smells like exhaust really bad under the hood no check engine lights. And I can't find a regular EGR it has this electric big thing on the right backside of the TBI unit is that a electric EGR? Should I take that off and clean it? When I unplugged it the check engine light came on just don't??????? then turned the key off and it went away She had a new fuel pump and filet and that other stuff less then 7.000 miles ago. Could it big the IAC unit or is that a electric EGR valve that I am seeing on the right backside of the TBI unit??? I am lost and would take any help I can get I am disabled and can't afford to pay for it let a loan tow it some where. Please and thank you for your time. Eric from so cal

Response From Hammer Time

That is the EGR. You can take it off and see if it is stuck open but you seem to be describing something worse than what an EGR valve would cause.

Response From giddyuperic

Thanks I did not say but it smells really bad like exhaust under the hood when it is running if you want to call it that. And on the electric EGR it has part of it that you can see that is not dirty and every thing else around it is it is part of it that sits right up against the intake and it is silver you can move it a bit with a little pry bar I did not force it being that is a electric component. So what else could it be then. It was running fine perfect all day all the way tell I turned the key off that evening. Running great and then jump in it the next morning and it won't idle and sounds like it has a miss fire with the smell of exhaust and clears right up at about 3000 RPM and she had a tune up with a new fuel pump and filter 7.000 miles ago. Any help would be great. I am hoping it is some thing simple I am a disabled vet and only make so much per month and have to count my pennies to keep my head above water each month. Thank you for your time. Eric p.s. I found some hoses that were bad and replaced the vacuum hoses. Id the only EVAP can the one by the washer fluid bottle is that it??? Thanks

Response From Hammer Time

You obviously have no idea how an EGR valve works. You don't pry on anything. You remove the 2 bolts that hold it on and remove it to see if the pintle is fully seated.

Response From giddyuperic Top Rated Answer

I know what it does it is a exhaust recirculating valve it put gas back in to the combustion chamber to prevent N02. I did not pry on it I just touch it to see it that was free and moving. I thought this site was to help people not be little them. I know about cars but I am not pro just enough to get by spent my life in the ARMY and I am a disabled ARMY vet and can't bend over the hood for more then ten minutes at a time so this is very hard for me and I was just trying trying get a little help. I am not that dumb to pry on any thing poor choice of words I know I have to take it off and put node light on it and see if it has power and power it up to see if it working. Maybe there is carbon holding it in the open or not. I don't know enough about the electric ones I know that you can just pull up on reg one and see if the car stumble's or put a vacuum pump on it and pump it up that way to but I don't know any thing about the electric ones so I guess I will just have to take it off and go from there.