306 hdi in tank lift pump problem

[scfc_151]

Ive had this problem for ages now but just as im messing around with our cars im trying to get to the bottom of the problem.

I fitted a in tank lift pump a while ago after a catestrophic fail and its been great.

However from time to time when I turn the ignition on it fails to start. It keeps turning over but not starting. Since ive moved house and park the car in my garage I can hear that the lift pump doesnt always kick in. You have to listen carefully but theres an obvious high pitch noise when it does kick in.

Im wondering if there is a problem with the ignition or could it be a relay thats at fault?


Cheers

[CitroJim]

Sounds like the new lift pump is a bit iffy. Often one that fails to start can be provoked by giving it a wallop. This is not a bad test as it'll prove the electrical supply without needing to get meters out and prove positive the pump is not happy.

The pump is fed via the double injection relay. In the Citroen HDi this is often next to the ECU and is a big double-length relay containing two relays in one housing. These relays are normally pretty reliable.

The relay itself is operated via the ECU and immobiliser. Next time the pump fails to run check that the car has successfully de-immobilised itself when the ignition is turned on. Again, I don't know about Pugs but on Citroens there is a light that stays on if the immobiliser fails to unlock along with a bleeping sound.

The supply to the pump can be checked with a voltmeter at the connector on top of the tank. The pump supply is the two thickest wires. The thin ones are the fuel gauge sender.

[CitroJim]

Just one further thought. Rare this but I've heard of one case where a new pump failed shortly after the old one really failed badly and the new one was found to have a little piece of debris jammed in it that prevented it from rotating. The debris was assumed to have come from the old pump.

[scfc_151]

Hi

Thanks for the reply, the RAC man did the old Fonze bang on the tank while I turned it over and it started when I originally broke down. I was well impressed.
There is no way on my car to know if the immobiliser hasnt worked before starting the car.

Because theres a whine from the pump when it works and its only occasionally that when I turn the key I dont here the whine and therefore the car just turns over, I get the feeling the pump works ok. I might be way off but my thoughts are towards the ignition because its intermittent. Could this be a possibility?

For instance if I turn the key and dont here the whine if I do it again then I will here the whine and it will start. I know I could just keep doing that but I dont want it to get worse and then one day it just doesnt start.

cheers

[CitroJim]

It could well be the ignition switch. A simple voltage check on the pump will confirm that to an extent. Next time it happens see if wiggling the key makes a difference...

[Lighty]

The multi relay on the 306 is between the ecu and the bulkhead, a bit harder to get too than a xantia, but exactly the same bit.