Discussion
car wouldn't start earlier but after a while fired up ok , went for a drive and engine completely died can't hear the pump priming now when i switch on ignition its has an upgraded pump and wiring , could someone please tell me where the relay is situated and any other problem it could be the car is a 2.5 and what part no i may need to get thanks
More info on my fuel pump problem:
I have an upgraded fuel pump (Bosch 056 254 044) which has been wired with an extra relay by the pump. This relay appears to have been wired in series with the original fuel pump relay as when I remove the original then the new relay doesn't switch. Both relays only stay on for less than 0.5 second !!! I have checked each relay (connected 12v between 86 and 86) and measure the resistance between 30 and 87 on each relay and got 0 ohms or short circuit so each relay is good.
This has had a new ECU installed (MBE9A5).
My understanding of how the system works is this:
1) The ECU should control the relay(s) coil(s) to enable the 12v to the pump to prime it for approx 2 seconds.
2) After this the ECU turns off the relay until it sees revs from the engine via the CAM timing or RPM. (Is this correct?).
3) As stated above both relays only stay on for less than 1/2 a second so the pump never starts up.
4) I have wired 12v to the pump separately and the pump works and car starts okay.
Is there a current sense circuit on the ECU for the return from the relay that the ECU detects that the relay has switched on or is it a dumb circuit and just runs of a 2 second timer?
Has anyone any ideas on this ECU? The car did drive okay from Leicester to Bristol ok after I had the ECU fitted but has now packed up due to this fuel pump issue? Is it recommended to have the original fuel pump relay and the extra relay (by the pump) in series?
Does anyone have any ideas why the ECU is only holding the relay coil voltage for less than 1/2 a second.
Many Thanks in advance
J
I have an upgraded fuel pump (Bosch 056 254 044) which has been wired with an extra relay by the pump. This relay appears to have been wired in series with the original fuel pump relay as when I remove the original then the new relay doesn't switch. Both relays only stay on for less than 0.5 second !!! I have checked each relay (connected 12v between 86 and 86) and measure the resistance between 30 and 87 on each relay and got 0 ohms or short circuit so each relay is good.
This has had a new ECU installed (MBE9A5).
My understanding of how the system works is this:
1) The ECU should control the relay(s) coil(s) to enable the 12v to the pump to prime it for approx 2 seconds.
2) After this the ECU turns off the relay until it sees revs from the engine via the CAM timing or RPM. (Is this correct?).
3) As stated above both relays only stay on for less than 1/2 a second so the pump never starts up.
4) I have wired 12v to the pump separately and the pump works and car starts okay.
Is there a current sense circuit on the ECU for the return from the relay that the ECU detects that the relay has switched on or is it a dumb circuit and just runs of a 2 second timer?
Has anyone any ideas on this ECU? The car did drive okay from Leicester to Bristol ok after I had the ECU fitted but has now packed up due to this fuel pump issue? Is it recommended to have the original fuel pump relay and the extra relay (by the pump) in series?
Does anyone have any ideas why the ECU is only holding the relay coil voltage for less than 1/2 a second.
Many Thanks in advance
J
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