Common Codes

Audi Q7 p008700 Fuel Rail / system pressure - too low

Cascade Fault Code: •

Affected Models: Audi • VW • SEAT • Skoda •

Audi Q7 3.0l TDI CRCA

P008700 Fuel Rail / System pressure - too low 

This Car initially came in with the light on, unfortunatly the customer couldent leave the vehicle for full diagnostics.

The car then stopped and wouldent restart so it was then arranged for recovery this does show that sometime its best to fully diagnose before the customer gets the car back.

So moving forward the lift pump at the rear was working and supplying fuel on engine cranking but it was noted the engine sounded lumpy on cranking.

it was decided to remove the injectors and do a leak off test the injectors were plumbed in but not into the engine with a small cup under each injector to catch the fuel it was immediatly obvious that the problem was one injector had failed with fuel pooring out of the nozzle when the engine was cranked this is why there was low fuel pressure as the injector was leaking so badly that no fuel pressure was able to build up its like filling up a bucket with a hole in it!

The lumpy sound was caused as the excess fuel in the cylinder bore was causing greater compression on that one cylinder causing the engine to slow down as it tried to compress so much fuel. 

The injector was replaced and all was perfect. 

Published • 2021-07-01 19:57:53 • 0 Comments