Fuel pump relay, crank sensor or a tired loom? A logical order for chasing a no-start on the 10P and 15P Td5.
A Td5 that cranks but will not fire is rarely a mystery once you stop guessing and start in order. Throwing a new crank sensor at it because a forum said so is how people end up with a box of new parts and the same fault. Here is the logical sequence we follow on the 10P and 15P engines before anyone reaches for the parts catalogue.
Does it have fuel pressure? Turn the key and listen for the in-tank pump prime; a Td5 needs pressure at the rail before it will fire. On the 15P the fuel pressure regulator is a known weak point, and a lazy pump or a leaking FPR shows as long cranking and eventual, reluctant starting. Confirm fuel before you chase anything electronic.
With fuel confirmed, three parts cause most no-starts: the crankshaft position sensor (no signal, no injection), the fuel pump relay and its tired contacts, and the immobiliser side — including the infamous injector harness, the "spider", whose internal wires chafe and short. A weak battery muddies all of it by dropping cranking speed below what the sensor needs, so start with a known-good battery.
This is where a Nanocom or Hawkeye earns its price. Watch live data while cranking: is there an engine-speed signal from the crank sensor, and are the injectors getting their feedback? A minute of reading tells you whether you have a sensor fault, a fuel fault or an immobiliser lockout — and turns a day of parts-swapping into a targeted fix.
The injector harness (the "spider") is the classic hidden Td5 fault: its wires chafe where they leave the cover and short intermittently. If the fault comes and goes with engine temperature or a knock on the loom, suspect the spider before anything else.
Diagnose in the order the engine needs to run, and the fault has nowhere left to hide.
Ivan Petrov · Master Technician
Book it into the Ram Parts workshop, or order the parts and do it yourself — either way you get the same advice.
