1996 GMC Sierra 6.5 turbo diesel 160,000 miles. due to stalling replaced/RELOCATED PMD module. replaced fuel filter,fuel pump relay, fuel tank and fuel pump. Ran fine after PMD was replaced. Now vehicle stalls again but fuel pump relay under the hood chatters. After 10 minutes vehicle will start back up, run about 4 -40 miles and stall again. Took it to the dealer, said I need to replace the fuel injector pump and throttle position sensor. Why would this cause my relays to chatter? At one point disconnecting my battery ground for 15-20 seconds would "reset" everything but now when it acts up the relays chatter off and on quickly. After 5-10 minutes the vehicle will run again.
Year: 1996Make : GMCModel: sierra 2500Engine: 6.5 l turbo diesel
replaced and relocated PMD
replaced batteries and battery cables
replaced fuel tank and fuel pump
replaced fuel filter housing and fuel filter 4 times.
replaced fuel pump relay when chateering started.
checked grounds on engine
disconnected ground from battery would sometimes cause chattering to stop. No longer the answer to stopiing chateering of fuel pump relay once it starts to act up. Engine cranks but will start when this occurs. Glow plug indicator light also will not light when relays are chattering. Service engine light flickers off and on as relay cycle on and off. Engine runs fine when relays are not shutting off and on.
From what you are describing, I would have to say the dealer is right. You need to replace the injection pump. There is a solenoid coil in the pump that is run by the PMD. When this solenoid shorts out it cuases the engine to stall. THis short in the solenoid could also cuase the relays to kick on and off. I would have the pump replaced and timing set first and see if relays work properly.
16 years GMC technician, 21 years Gm Mater certified, 21 years ASE certified