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Old 07-18-2019, 09:17 AM   #1
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Should EGR diaphragm hold vacuum?

I attempted to check egr by applying vacuum on the upper port. It would not hold vacuum, which leads me to suspect that the diaphragm has failed. However, I am not very familiar with these valves. Does the presence or absence of vacuum at the little, upper vacuum port simply open and close the large exhaust port? If so, does the application of vacuum open or close the large port? If it is faulty, is there any reason to delete the egr system all together, or simply repair to stock condition?
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Old 07-18-2019, 09:29 AM   #2
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An EGR valve being tested as you stated should hold vacuum for at least one minute. If it doesn't I would think its either out or on the way out.

What year/motor is this?
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Old 07-18-2019, 09:40 AM   #3
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Originally Posted by MinntoMich View Post
An EGR valve being tested as you stated should hold vacuum for at least one minute. If it doesn't I would think its either out or on the way out.

What year/motor is this?
1999 Fleetwood Bounder 28T. 6.8L, 2 valve.

It had a lopey idle when we bought it a couple months ago. Pulled intake to replace knock sensor gnawed in half by a varmint. Trying to check everything so when it’s back together it will be “right”. So far compression is good. New plugs and coils, new water pump and heater pipe, new belts and hoses....now new egr.
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Old 07-18-2019, 09:51 AM   #4
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Quote:
Originally Posted by Fugitive861 View Post
I attempted to check egr by applying vacuum on the upper port. It would not hold vacuum, which leads me to suspect that the diaphragm has failed. However, I am not very familiar with these valves. Does the presence or absence of vacuum at the little, upper vacuum port simply open and close the large exhaust port? If so, does the application of vacuum open or close the large port? If it is faulty, is there any reason to delete the egr system all together, or simply repair to stock condition?
Yours probably will not hold a vacuum. The newer EGR valves are a pressure feed back design which will have a small hole to let air in to the diaphram chamber to buffer the valve.
Take your vacuum tester to the store who has a valve for your application and test the new valve to confirm this.
Lynn
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Old 07-18-2019, 12:18 PM   #5
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Yah, it should hold vacuum. When I installed my headers, I removed mine and put a blank plate over it. I rerouted the vacuum lines to spoof the sensors into thinking it was working.
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Old 07-24-2019, 09:19 PM   #6
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Well I tried pumping the vacuum pump as fast as I could and the valve never budged. I assumed the diaphragm was faulty. I cut it open to confirm my suspisiones only to find out all appeared in order. The “bypass” hole was larger than I could compensate for with my little vacuum pump. So, I learned a $50 lesson...new egr on the way.
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Old 07-25-2019, 12:51 AM   #7
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Yah, it should hold vacuum. When I installed my headers, I removed mine and put a blank plate over it. I rerouted the vacuum lines to spoof the sensors into thinking it was working.
Put the EGR valve back on, get it working properly, advance the ignition timing and you'll not only have more power, but better gas mileage. EGR can be a good thing for both power and fuel mileage. I've even put EGR systems on engines that didn't even come with them stock.
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Old 07-25-2019, 12:57 AM   #8
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Originally Posted by Fugitive861 View Post
Well I tried pumping the vacuum pump as fast as I could and the valve never budged. I assumed the diaphragm was faulty. I cut it open to confirm my suspisiones only to find out all appeared in order. The “bypass” hole was larger than I could compensate for with my little vacuum pump. So, I learned a $50 lesson...new egr on the way.
Most EGR valves are either positive or negative backpressure controlled. Meaning they will NOT pull the diaphragm up with a hand pump unless they have the exhaust system pressure on the other side of the valve.
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Old 07-25-2019, 04:57 AM   #9
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Originally Posted by Fugitive861 View Post
Well I tried pumping the vacuum pump as fast as I could and the valve never budged. I assumed the diaphragm was faulty. I cut it open to confirm my suspisiones only to find out all appeared in order. The “bypass” hole was larger than I could compensate for with my little vacuum pump. So, I learned a $50 lesson...new egr on the way.
You may find carbon build up in the exhaust passages under the EGR valve which will prevent the EGR valve from receiving enough exhaust pressure to open the valve when it is commanded on.
As I said in post #4 these valves are a pressure feedback design. They will not open with vacuum alone.
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Old 07-25-2019, 05:23 AM   #10
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Put the EGR valve back on, get it working properly, advance the ignition timing and you'll not only have more power, but better gas mileage. EGR can be a good thing for both power and fuel mileage. I've even put EGR systems on engines that didn't even come with them stock.
There is a great deal of discussion on EGR deletes on the Ford forums. The general consensus is that removing the EGR will not increase HP or MPG. AND, under certain operating conditions, deleting the EGR could cause a decrease in HP or MPG.

No one who had actually deleted the EGR reported a decrease in HP or mpg.

The theory was that the PCM commands EGR only under certain conditions, i.e. low power cruise. Since most of the truck people who were performing the delete never operate in the "low power cruise" area of the envelop, their EGR is rarely, if ever active.

Unfortunately, I can't confirm any HP or MPG change as a result of EGR delete, because I made to many other changes (Exhaust headers). I suspect in my case, the EGR delete made no difference in engine performance.

One of the tests I'll make on my next trip is to wire a light to the EGR solenoid so I can see when its energized. This will verify the theory of low power cruise operation.


..
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Old 07-25-2019, 06:36 AM   #11
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My experience with EGR valves is limited to Ford products. Yes the valve should hold vacuum. There is an internal spring to reseat the valve when the vacuum is removed.

There are 2 more components in the DVD system. The EGR Vacuum regulator (which does have a calibrated leak to allow the vacuum out when turned off) and the Differential Pressure Sensor that measures EGR pressure on both sides of the valve to determine flow.
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Old 08-06-2019, 05:21 PM   #12
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Update. New egr holds vacuum, so I went back and took a closer look at old one. What I thought was a calibrated hole could not possibly work. Vacuum may pull the diaphragm up but the needle connected to large valve would never move. It looks like maybe a clip of some type may have held the pin in the center to the diaphragm. Well, that is probably more egr valve information than anyone cares to know.
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