Fuel pump not priming: what to check before you replace the pump

Start with the symptom

• No whine when the ignition goes on. Normally you can hear the pump prime. In the 2015 case it was silent, the engine turned over fine and there was good spark on all plugs, but the test valve on the fuel rail gave only the briefest squirt of fuel.
• The rail primes once. One owner said the fuel rail only primes once until the engine is running, so don't judge the pump from repeated key-on tests.
• Try the quick things first: the red fuel cut-off switch at the rear of the subframe on the passenger side of the engine bay (check the rubber button is pressed down), reseat the yellow starter relay, look for codes, and in one owner's suggestion, disconnect the MAF to see whether the car fires.

The fuel pump relay (K16)

• It is a grey relay, not the brown one. A moderator said you can't swap the brown ECU relay (K18) with a grey one, because the engine wouldn't run. Swapping the grey relays with each other is a fair test. See Relays and fuses (NA).
• Which pins do what. Pins 85 and 86 are the relay coil. The coil's switched 12 V (a white/violet wire) comes from the ECU through the blue "loom of doom" plug. Pins 87 and 30 are the pump power. If you read only about 0.1 V at the fuel cut-off switch, the relay isn't energising.
• Test across the relay socket. One owner suggested shorting across the relay socket to feed the pump manually. Another, in the 2018 case, jumpered across 30 and 87 on the back of the terminal block. If the pump runs, the pump is fine and the fault is in the relay or its feed.
• A relay can fail inside. In the 2018 case a brown relay tested open between 30 and 87 when powered. See P1512 and a car that won't start.
• Meter readings in the 2015 case. At the relay he read 9 V across 85 and 86 and 12 V across 87 and 30. The moderator pointed him at the coil feed through the loom of doom plug and the ECU plug.

The loom of doom plug

• Where. The blue and black plugs behind the coolant expansion tank. See Throttle failure and limp mode: the connectors to check for access and the pin list.
• The fuel pump feed. One owner said it is the only big, fat wire in the plugs, a thick pink/brown wire at one corner of the blue plug. Pull the yellow mesh part out of the plug and look at the terminal for green or white powder. Spraying contact cleaner won't shift that: the terminal needs replacing.
• What owners found. One owner's weak pump was corroded terminals in these plugs and it was quieter after he swapped them. Another had a dead pump, checked the current, fitted a new pump that blew in 10 miles, and then found the supply was intermittent and traced it to corrosion near the loom. After the wiring was repaired his third pump ran for around 1,000 miles and a couple of track days with no trouble.
• The pump plug. Check the terminals on the pump itself too. See Fuel pump replacement for the pins inside the plug that can spread.
• Boot wiring. One owner whose pump wasn't priming said to check the wiring and fuses in the inner rear arch liner in the boot. His had melted, and an auto electrician fixed it for about £40.
• Bypassing the plugs. The owner in the 2015 case said he would probably be cutting up the rear panel for a known fix that gets rid of the loom of doom plugs. We haven't seen the details.

Then the pump

• Don't run it dry. One owner pointed out that pumps can burn out fast if there is no fuel to pump, because the petrol both lubricates the pump and gives it something to work against.
• Replacement. See Fuel pump replacement. One owner had a spare original pump and said so on the thread, so used ones are around.
• Supercharged cars. If a supercharged car is slow to start rather than not starting at all, see Cold start: slow starting after a supercharger conversion.

The 2015 thread ends with the owner still tracing the supply, so we don't know what his fault turned out to be.