Thread: TD5 knocking noise with ignition on but engine off

Originally Posted by DylanTD5

I’ve searched and couldn’t find anything.

When I turn my ignition on, but not start the engine, I get a knocking noise from the engine bay. Sounds like someone is tapping a hammer on the firewall, and will do it 20-25 times in about 10 seconds. Happened every time I switch the ignition on, even if it’s only just been turned off.

I’ve only had the car for a few days so it may be normal, but it definitely didn’t happen when I test drove/drove it home.

In my experience ( 11 years ownership & 220,000kms driven in that time ) it is not normal. However with the ignition switch in the position that you describe the fuel pump will be running to build up pressure in the fuel lines and pressure regulator so the only thing that I can think to look for is a ‘loose’ or unsecured fuel line - and is that even a feasible cause for what you are hearing ? I gotta say I absolutely don’t know.

I have a couple of suggestions.
1 The heater blower fan has something in it and is knocking until gaining speed. I had a ball point pen drop into mine via the demister vent.

2 even though it is not that loud the aircon heat sampler on the RH of the steering column can block up with fluff.

3 the fuel pump goes for several seconds before engine start. I cannot think of anything in the engine bay that makes a noise with ignition on before start up.
Has it got a second battery and relay controller?
Regards PhilipA

Thanks for the suggestions, I’ll check them out tomorrow morning.

It has a second battery with DCDC charger, but it makes the noise with that disconnected. My Nanocom arrived today and it’s not throwing any fault codes, and drives fine.

also check the aircon clutch although it shouldnt come in until after the engine starts but sometimes they can clunk.