EGR Valve Test
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Laughing Gas
Joined: Mar 2015
Posts: 885
Likes: 2
From: Pittsburgh
EGR Valve Test
I believe that I have a bad EGR valve. I attempted to test it while it was off the truck during my carb rebuild. I cleaned out all the carbon with a pick and carb cleaner from the valve and the spacer.
I can work the diaphram with my finger. It travels seemingly freely and when I compress it, the vacuum connection lets out a nice little "poof" which says to me that the diaphragm at least isn't completely blown.
I tried to apply vacuum from one of my other cars and then with a hand pump and both were unsuccessful at holding any vacuum pressure or making the piston move at all to open the exhaust port. I then decided that I must have at least some sort of hole in the diaphragm and the unit needs replaced...
But before I spend $50+, can someone confirm one little thing... I read that some brands of EGR valves require exhaust backpressure while receiving vac pressure in order to move the diaphragm. This is the original Ford unit. Did I test it right meaning that it needs replaced, or do I need to put it back on the truck and do the other tests like spraying carb cleaner into it, etc.?
I can work the diaphram with my finger. It travels seemingly freely and when I compress it, the vacuum connection lets out a nice little "poof" which says to me that the diaphragm at least isn't completely blown.
I tried to apply vacuum from one of my other cars and then with a hand pump and both were unsuccessful at holding any vacuum pressure or making the piston move at all to open the exhaust port. I then decided that I must have at least some sort of hole in the diaphragm and the unit needs replaced...
But before I spend $50+, can someone confirm one little thing... I read that some brands of EGR valves require exhaust backpressure while receiving vac pressure in order to move the diaphragm. This is the original Ford unit. Did I test it right meaning that it needs replaced, or do I need to put it back on the truck and do the other tests like spraying carb cleaner into it, etc.?
Laughing Gas
Joined: Nov 2013
Posts: 1,207
Likes: 60
From: S.E. Louisiana;so far USA
Sometime it can be helpful in a diagnosis to know the year of manufacture and the engine in question. The Ford shop manuals have much written about diagnosing and service procedures for the EGR system. I'm looking at the 1977 Ford truck shop manual. It has 6+ pages dedicated to the subject of the valve itself. Reading such material may provide some clues to help with your diagnosis. Backpressure is covered in some of the procedures. There may be some shorter expeditious way of testing which I am unfamiliar with. Perhaps other members will contribute.
Last edited by Ozzie H.; Oct 30, 2015 at 08:43 AM. Reason: Added information
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