PFahlberg
01-03-2007, 16:03
My truck is a 92 GMC 6.2 "J" with OEM frame rail mounted pump.
Changed the fuel filter. Jumped pump fuse on firewall passenger side to prime system, plenty of flow. Hooked test light into pump fuse circuit, light illuminates when cranking, goes out when engine starts key switch released from crank position. With engine running, opened fuel bleed valve at front of engine, engine stalled. Dash has oil pressure gage which functions, shows normal oil pressure. Had helper listen to lift pump during cranking, pump works. Had helper listen to lift pump with engine running, pump did not work, jumpered pump circuit with engine running, pump works.
Tested fuel pump relay by removing CRNK fuse, applied 12V to purple wire on relay harness, relay clicks, lift pump operates.
My Chilton manual has diagrams which help me understand how the lift pump circuit functions when cranking, but the running circuit is not shown.
Anyone know what to do here?
Thanks in advance.
Changed the fuel filter. Jumped pump fuse on firewall passenger side to prime system, plenty of flow. Hooked test light into pump fuse circuit, light illuminates when cranking, goes out when engine starts key switch released from crank position. With engine running, opened fuel bleed valve at front of engine, engine stalled. Dash has oil pressure gage which functions, shows normal oil pressure. Had helper listen to lift pump during cranking, pump works. Had helper listen to lift pump with engine running, pump did not work, jumpered pump circuit with engine running, pump works.
Tested fuel pump relay by removing CRNK fuse, applied 12V to purple wire on relay harness, relay clicks, lift pump operates.
My Chilton manual has diagrams which help me understand how the lift pump circuit functions when cranking, but the running circuit is not shown.
Anyone know what to do here?
Thanks in advance.