Fuel pump not always priming

colintinto · Post by **colintinto** » Thu Sep 15, 2011 9:23 am

Hi All,

Just noticed this recently - occasionally when I'm starting the car, I turn the key to the position where the fuel pump usually 'primes' and I don't hear anything. The car will still start, but might take 4-5 turns rather than the usual 1-2.

It does work sometimes, and it doesn't appear to be related to whether the engine is cold or not.

Electronic issue or fuel pump on it's way out? Is it hard/expensive to fit a new fuel pump?

Colin

Post by **Shug** » Thu Sep 15, 2011 10:22 am

There could be about a dozen reasons - none of them the fuel pump itself. (ask me how I know - I've had them all) In order, this is what I'd check when it doesn't prime:

Fuel pump fuse - holder is cheese and it could be corroded - standard part, so halfords fix. Even if it's not corroded, the spades can get tired and start intermittently connecting with the fuse.
Inertia switch - these can get dicky - bridge the connections in the plug with a paper clip as a test - cheap to get replacements on the 'bay
MFRU (Relay pack) - sticky relays, or water ingress. If you suspect water, open it up and look for signs of ingress - there are just tabs to depress and it slides open

Then you're looking at immobiliser (although not if the engine will spin on the starter)

Unplug all the connectors to these bits and give them some WD40 love, see if anything's corroded or the like.

The pump is still possible, but very very unlikely in the case of an intermittent fault like this.

Dominic · Post by **Dominic** » Thu Sep 15, 2011 11:05 am

Mine does not always prime;

If I get in and turn the ignition on and the immobiliser is still on, I press the key fob button (with the ignition still on) - disarm the immobiliser, the fuel pump wont prime, but the car does start. The pump primes every time if the immobiliser is off before I turn the ignition key.

Post by **Shug** » Thu Sep 15, 2011 11:11 am

There's also that

ceejam · Post by **ceejam** » Thu Sep 15, 2011 11:33 am

The pump also won't prime if the ignition's been off for a short time (around 30 seconds) as the ECU won't have powered down.

robin · Post by **robin** » Thu Sep 15, 2011 11:38 am

It's a sequencing issue as has been suggested above.

If you disarm the immob before turning key to run position you should always hear the pump prime.

On the S2 the turn off delay is pretty short - from key off to MFRU off is about 5 seconds (it was longer on S1 for some reason).

Cheers,
Robin

Post by **campbell** » Thu Sep 15, 2011 4:08 pm

Yep, similar behaviour on mine, Colin. If your pattern is as described above, carry on driving

Scottish Elises