how do i test my egr valve for my 1979 ford f150 351m

 

I have used a hand pump with vac gauge to test mine. You can hook it up to the valve and check to make sure it is opening and that the diaphram is not bad using the pump and making sure the gauge holds vacuum. I will usually put something against the valve diaphram to make sure it moves when the vacuum is applied. I would also imagine that if you engaged the egr at idle you idle should change since you have just diluted the air/fuel mixture. You can also use a T in the vacuum line to the egr valve to check that it is being opened at part throttle with higher RPMs. I am sure people much more qualified than me will answer your question more thuroughly, but hopefully this gives you something to start with.

 

well when i went in to buy a new one because mine wasnt folding vaccum, the ones at auto parts stores didnt hold vaccum ethier on the table so does that mean the ones at the stores are bad or good if they dont hold vaccum off the car

 

If you stick a blunt object under the EGR while the engine is running then push up on the diaphram the engine will most likely run rough or even stall if its working correctly.

 

That doesn't tell you whether or not the valve itself is working. You're just manually forcing the EGR valve open to introduce exhaust into the combustion at idle. Yes, the engine will run rough in this case, but it will still do this even if the valve diaphragm is ruptured and the test won't tell you anything.

nickbaize, I'm settling the score on this for good. I went out to the shop, and got out a new, known-good EGR valve. I put a short length of 3/16" vacuum hose on it, and applied vacuum. The spindle moved inward. While still applying vacuum, I pinched off the line and then removed the vacuum source. The valve held vacuum and the spindle stayed in. I let off the line, and the spindle popped back out.

The spindle of a properly working EGR valve will move inward with vacuum applied, and it should hold that vacuum as long as the input port is sealed. That's all folks.

I think this is the third thread you've started on this. Each time I've explained how it should work, and this time I even checked for you myself. If you're not able to repeat my procedure, either the valve(s) are bad or you are checking incorrectly.

 

Thanks for clarifing this.

 

No problem

 

ok thanks guys

 

Does the EGR have to be off the carb to see the spindle move with vacuum applied?

 

Depending on the valve, you may be able to see the rod coming off the back of the diaphragm move. If not, it's only two bolts to remove the valve from the spacer plate and look at the actual spindle.

 

Thanks. I can see behind the EGR looks like the back is open. Vacuum to it didn't move the inner plate and it could hold a steady vacuum. I guess I will take it off and see if it moves.

 

For anyone with a 78' CA EGR, applying the vacuum to the valve while off the vehicle will not tell you if it works. Had the original and two replacements and neither did anything with vacuum applied. Put them on the vehicle and they worked fine. Revved the warmed up engine to 2000+RPM's and the diaphragm moved as it should. They must need the back pressure to work properly. The instruction sheet that came with the BWD EGR valve also states that a off vehicle test will not show a bad valve. Not sure if this info applies to other year valves.