I have hard break peddle with little breaking power. I checked the vacum pump a found 13 inches of vacum. the hose removed from the vacum booster will **** your finger to it with motor running. the truck is a 1997 f350 7.3 liter diesel

I have ford f250 91 diesel but i don't now were the vacuum pump is locate i need diagram please

Hello, Check other Vacuum lines for leaks. If you have a 4x4, they can have Vacuum operated hubs and a leak anywhere will draw down the Vacuum. I found most pumps running at about 21psi. Check for a Vacuum Reservoir. The older models used one looking like a coffee can and they would rust on the bottom and leak.

If you take off a vacuum line and use a hand vacuum pump, you should easily find a leak on one of the remote lines. Another test idea is to remove the Vacuum pump lines, put in soapy water, and pressurize with about 3 PSI. Any vacuum leaks will blow bubbles and soapy fluid. Its your choice on what to do. I would reserve the soapy water for a line I find to leak with a hand Vacuum pump.

Many of the people wih your problem replaced the vacuum pump and were good to go. But if you can measure the vacuum and find the leak, you may save money on a part you do not need.