Hi,

I've got an 85 F-150 with a 4bbl carb. I want to verify that the EGR is working. I took it off and plugged it into a vacuum line on my other truck... that line pulled 20 inches of Hg. The EGR I tested didn't move.

I went to the salvage yard to get another one and all four that I pulled and tested did not move when connected to vacuum.

Am I testing them wrong? How should I verify their operation?

Thanks,
Sal

 

It doesn't take a large amount of vacuum. You can generally hook a hand vacuum pump (like a Mity Vac) to the EGR with the engine idling and pull a vacuum, if the idle speed drops and the engine stumbles and/or stalls, then it's working and the passages are clear. I've seen the EGR itself be functional but the passages so choked with carbon that the valve's opening made no difference.

You must have just gotten four bad ones in a row. If you're hooking it up to a strong engine vacuum like that and getting no movement, the EGR must be bad. Try pushing on the pintle in the the opening where it bolts to the manifold and see if it moves away and then retuns to close the valve when you release it. If it moves freely, then apply a vacuum to it. and see if it moves on it's own.