I've got no cruise control, brake/abs lights are on and 4x4 light won't come on. How do I test that pump? It's my 1997 3500 4x4. Thanks.

 

Cant give the specifics as I don't recall the numbers but a vacuum gauge hooked up to the vac line coming off the pump will give you the reading you are looking for. I want to say it is mid to upper 20's is what you are looking for but I may be wrong. You might also look for a broken, split, unhooked vac line. Just last night I took my truck out and noticed my fan was only running through the defrost vents and then my 4x4 would not engage. Got home opened the hood and viola the vac line had come unhooked up at the firewall. Hooked it back up and was back to normal.

 

If functioning properly you should see at least 25 inches of vacuum. I think mine peggs the vacuum gauge at 28-29in/hg

 

Upper 20's, but first check the line from the pump to the vacuum distributing t at the drivers side cowl.

It is very easy to pull the vacuum line out at the cowl when you are working on things.

Won't cause the brake/ABS light on the 97's though.