chueseman

I have a 1995 XLT automatic 5.0 liter 4x4. The error message from the Check Engine light says that the EGR valve is not opening. The first problem was the EGR diaphragm was shot. I replaced both the valve and sensor and it now works properly when tested with a vacuum pump. The second problem was that the vacuum canister was shot. That was replaced and is correctly pulling a vacuum. Lastly, I checked the vacuum going to the EGR when the engine is started. There is no vacuum. Therefore, the error message is still correct. I have also replaced the sensor on the air intake tube a foot or so away from the engine. Yes, I have always disconnected the battery and each phase of testing to remove the error message. I have a "1995 F-series Electrical and Vacuum Troubleshooting Manual". Out of a 150-page manual, there only 1 page devoted to vacuum and it is so generic that it is totally useless. I assume that as the engine starts, the main Module sends a voltage to some solenoid which opens and pulls a vacuum going to the EGR valve. I also assume after X number of seconds or after the EGR sensor knows a vacuum has been pulled, the voltage to the solenoid is turned off and vacuum to the EGR valve is released.
Assuming that there is indeed a solenoid controlling the on/off vacuum going to the EGR, I have no idea where it is. Testing that would greatly help identify the problem. Alternately it could be that one of the vacuum lines on the engine is broken, but I have no idea on the exact testing order to determine where the break is. Any thoughts?