02, xk8 ragtop. No fuel pressure, pump not running so just fitted a new one and the problem remains. I can get the pump to run by jumping the switched terminals on the relay base so I know the pump is ok (wish I'd done that before changing the unit ). Swapped the relay with another and no change. All fuses ok. There is power to the coil in the relay but it's not being switched by the ecm. All suggestions of things to check welcome, in particular des anyone know what sensors/switches have to be 'OK' for the ecm to switch on the pump?

(if anyone thinks this is familiar, it is! I started trying to sort this about two years ago but losing both my parents tends to throw a spanner in the works)

 

Have you tried to reset the shut off relay in the "facia" fuse box (the one that you access with the doors open)? It is supposed to engage in an accident and cut off power to the fuel pump and a majority of other circuits. It sometimes trips and need to be reset manually. The exact name escapes me at the moment, but it is below the fuses, likely driver side.

 

The Inertia Switch is located in the left hand side fuse box area. See attached layout..

 

Thanks guys, I did check this originally but will jump the terminals so it's out of circuit.

 

Ok, tried with the security sounder reconnected and no difference. I have removed it now to see if it's repairable but that's for another day.

i put a link wire across the pump terminals in the relay base so the pump runs all the time and tried to start the engine, no go. It turns over ok but isn't firing so the problem is effecting the injection and or ignition too, this certainly points to be cut off switch but it's pressed down as it should be. I'm struggling to get into the dash side fuse panel though because the car is in the garage and I can't open the door wide enough.

Did get a P code, 1230 which is fuel pump relay failure! I know it's not a faulty relay because I've both tested and substituted it.

 

If you turned the key to ON with the relay out of the socket (connected your 'jumper-wire') then YOU set the P1230 DTC. Just ignore that for now.

 

ok, good to know, thanks.

 

I'm afraid the problem is located elsewhere than the pump or the pump supply.

In case the ECU does not trigger the fuel pump relay, that could probably because the ECU does not recognize the movement of the flywheel.
Could this be an option?

BR
Ralf

 

Interesting thought Ralf but the pump should run before the flywheel turns. Also I'm either not getting ignition or fuel injection happening.

 

Definitely not the inertia switch. I removed it and when tapped it tripped so it was in the 'run' position.

 

That fits perfectly into the picture!
If the ECU does not know where the Crankshaft is, how should it know when to inject or ignite?

 

Knew I'd read this somewhere. From the 881 training guide (my emphasis):

"
In normal operation, the ECM uses the inputs from the crank sensor and the A bank cam sensor for cylinder identification
and ignition/fuel synchronization. If the A bank sensor system fails, the ECM switches to the B bank inputs. If
the crank sensor system fails, the engine will start and run using the inputs from both cam position sensors."

Do you now have fuel pressure at the Schraeder valve? Bear in mind that the pump will only run briefly (~2 seconds) when the ignition is switched on, until the motor starts.

Are you picking up from where you left off in 2018, or has the car run since?

 

Great Info, Michael,

I was of the opinion the camshaft sensors only giving one position signal per rotation, not a continuos one. With the VVT in place this migth be different! Agan something learned. Thank you!

Next guess: from the Technical Guide MY 2003 about the functionality of the immobilizer system:

"If the key is turned to the ignition Run position, the instrument cluster will start the CAN
data exchange and start transmitting the idle status. If the key status is valid, and the
subsequent challenge / response is verified by the ECM, the ECM will allow the engine to
start. Otherwise, starting of the engine is disabled. The ECM controls the following outputs:
starter relay, fuel injectors, ignition coils and fuel pump.
The ECM will disable the fuel injectors, ignition coils, fuel pump drive and starter if any of
the following conditions apply:
• A theft signal has been received from the IC, i.e. the key code has not been
received/code does not match.
• A challenge code has been transmitted to the IC but no response code has been
received.
• A challenge code has been transmitted to the IC and an incorrect response received.
If any of the above cases apply, the ECM will log DTC P1260. This DTC is further defined by
sub-codes. The sub codes are accessed through freeze frame data. Additionally the IC will
log DTCs if the failure was a result of the key transponder exchange."

Have you REALLY checked every single Fuse to be intact?

BR
Ralf

 

True but wouldn't the ecm log a DTC if the sensor had failed? Also that wouldn't effect the fuel pump relay.

 

The typical startup I know from other cars is, that upon ignition turned on, the fuel pump relay turns on the fuel pump for about 2 seconds.
This is done for bringing the system pressure up and provide the injector priming pulse for starting up. If there's no signal from the crankshaft sensor detected, the fuel pump is switched off and not switched on before movement is detected.

But I do accept that a 2003 Jaguar is in this respect more complex than a 1996 Lotus

 

Hi Michael, picking up from 2018 I'm afraid (things happen slowly here lol).

I can get fuel pressure but only by putting a link across the relay base terminals.

My car is a single pump XK8 not SC version. The system has a flow and return pipe and in the past the pump has run continuously.

I would expect a DTC to be logged if any of the sensors was playing up but I've got nothing except the low fuel pressure one.

 

At this Stage I would connect a small Bulb across the Fuel Pump Relay Coil Contacts.
If the Bulb does not light up for 2 seconds when ignition is switched on, the problem is more towards the ECU.

 

Have done it with a meter, nothing showed.

 

Gear selector switches ok, will only crank in P and N.

 

2001 XK8 Conv. In storage. No start. No fuel rail pressure. Swapped fuse #7 (20amp) - no help. Swapped fuel pump relay. No help.

Time to dig out the wiring diagrams. On this car, The ignition switch closes on start/run to ground. This completes the circuit from the battery, through the Ignition Positive Relay coil, a diode, and the closed inertia switch.

The N.O. Ignition Positive Relay contacts then close, feeding battery power to fuse #3 (5amp), then to the Fuel Pump Relay coil, then on to the ECM output. The ECM output grounds the circuit ( to complete this circuit) in start/run.

The now energized Fuel Pump Relay closes its N.O. contact, connecting the battery to fuse #7 (20amp), then on to the fuel pump to run it.

So I guess I need to also check the Ignition Positive relay, as well as fuse #3 (5amp). I sure hope it isn't the ECM. Based on the fact that it has been in storage for several months, I'm betting it's the fuel pump has decided we have abandoned her, and has lost its will to live. My bad.

P.S. It's the fuel pump after all - dag nab it.

Here is a schematic - hope it helps