I have a 7.3 PSD from a customer that has been giving me absolute grief. Came in with intermittent shutdown faults, like it was running out of fuel. I scanned the ECM and found a few codes, patched all of that and fixed the wiring. Further diagnostics then pointed to the lift pump on the chassis rail. I replaced this and plumbed it up with clear fuel hose. After about 10km (I'm in Australia) the truck started to slowly lose fuel pressure again, eventually showing zero on the gauge and stalling. I fitted an auxillary fuel supply and it started straight back up again and got me back to the shop. Suspecting an in tank issue I pulled the tank and sender and found the suction foot broken off the tank, and the mix bowl screens badly blocked.
I modified the pickup to eliminate the screens and fitted another filter between the tank and lift pump. Started the truck again and off we went, returned it to the customer and they drove for about 4 hours before the same problem started again. Limped the truck back to my shop, removed the supply line from the back of the lift pump and used a smoke machine to search for any further pin holes that may be allowing air into the fuel. This test revealed a pin hole in the flexible line that goes from the sender to the steel line on the chassis. Replaced this and went again. I personally drove the truck for 3 hours with the fuel pressure never dropping below 60psi, before allowing the customer to collect it again.
Customer rings again today telling me that he managed to drive approx 12km before the fuel pressure dropped and the truck stalled again. I'm leaning towards maybe a sticky fuel pressure regulator? This is definitely the hardest diagnostic job I have had through in a while.
I modified the pickup to eliminate the screens and fitted another filter between the tank and lift pump. Started the truck again and off we went, returned it to the customer and they drove for about 4 hours before the same problem started again. Limped the truck back to my shop, removed the supply line from the back of the lift pump and used a smoke machine to search for any further pin holes that may be allowing air into the fuel. This test revealed a pin hole in the flexible line that goes from the sender to the steel line on the chassis. Replaced this and went again. I personally drove the truck for 3 hours with the fuel pressure never dropping below 60psi, before allowing the customer to collect it again.
Customer rings again today telling me that he managed to drive approx 12km before the fuel pressure dropped and the truck stalled again. I'm leaning towards maybe a sticky fuel pressure regulator? This is definitely the hardest diagnostic job I have had through in a while.