Chances are it's one of two things. Something wrong in the electrical, possibly a switch, or broken connection somewhere? Or it could be low oil pressure. If your oil pressure is low the jakes will either be very week or won't work at all. If your oil pressure is low you may need to have new rod and main bearings installed. These 671 detroits need to be wound up when driven anyways to keep the oild pressure up. The first time I drove one my boss told me if I blew the old truck up and he'd buy me a brand new one to drive. I tried every day doing just what he expected me to do, reving the hell out of it. LOL. He knew thats the way these older detroits needed to be run to keep the oil pressure up. Smart boss, he never had to buy me a new truck due to a blown engine. ; ) What RPM are you running, if your sitting at a idle flipping the switch on they probably won't work. The lower the RPM the weaker the jake. You need High RPM/High Oil pressure for them to work best. Hope that helps. |
