306 Won't start- fuel

[Premier 350]

Wife's 306 XSI won't start. I suspected fuel (about the only thing I've gotten correct thus far) and it started with some fuel down the inlet. 

Some googling and Aussie Frogs told me it was either the pump or the relay. I powered the pump up and it sounded OK. 
Am I right to make my next step a fuel pump relay replacement?

But why wouldn't it start with the pump running from a jumper battery?
It's doing my head in. 

Thanks once again.

[Mighty306]

Hi mate.  Sorry for the slow reply.  I don't check in here very often now.

A few questions for you.

> How fresh is the fuel in the tank?
> I assume you had pressure at the rail when you had the pump running?
> Also, how long did you take cranking it over with the pump running?  After I'd replaced the pump one time on mine it took a long time to catch afterwards - may have been an air lock somewhere I guess.

You're right that power for the pump is via the duel fuel relay, but is also dependent on the fuel cut-off switch not having been tripped (although unlikely without a collision).  Certainly worth a try replacing the relay as they can still be sourced very cheaply, although don't get an unbranded one (which are only about £10).  Assuming you have the 16v XSi then part number is 454935.  The Nagares ones are fine  Fits MAHLE MR 7 Multifunctional Relay OE REPLACEMENT | eBay.  Either that or second hand genuine Omron one.

The relay is powered from the ECU, and then goes on to provide power for more that just the fuel pump - also the injectors & the ignition coil.  As you said it will start with fuel in the intake then you have spark, which means the relay is at least partially working. If a new relay doesn't fix the issue then post back here. I'd have to dig out a wiring diagram to check if the coil & injectors are powered off different sides of the relay. (It has two separate controls).

[Mighty306]

Thought I'd update re the relay wiring anyway.  This assumes you have the 16v XSi with the Bosch MP5.2 ECU.

The ignition coil and the injectors are indeed powered from different sides of the dual relay.  If you want to do any testing, this is the pin data for the side of the relay that powers the injectors:

Pin 14 - Power for control side
Pin 7 - Ground for control side (provided by pin 36 on the ECU)
Pins 8 & 15 - Power to the supply side of the coil
Pin 13 - Power out to injectors (which are then grounded via pin 17 on the ECU)

If that side of the coil isn't working you'll also have no power to the throttle body heater, the EVAP purge solenoid, or to pin 37 on the ECU.  (These come from pins 4, 6 & 5 respectively on the dual fuel relay).