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
I was the person that posted (2) as I was assisting J in isolating the fault. The ECU runs the pump (via the relay) old or new for a couple of seconds to prime the injectors.. then stops it... that's the normal operation **IF** the ECU doesn't see the engine start either via REVS or CAM timing then it won't start the pump again. This isn't even getting as far as starting the pump.. The supply volts are on one side of the new relay and the relay very quickly tries to energise and switch the 12v over to the pump but only for less than half a second.. this is with the ignition in enabled mode.. not turning the engine..
Either the ECU is shutting it down quickly or there's resistance from the battery positive that's preventing enough current from flowing to the motor.. maybe a loose connection.
If there's and inline fuse we'll look there first if that gives a similar fault.. The cabling runs under the chassis to the battery... is the fuse near the battery or near the new relay? Can't see it there
P
Either the ECU is shutting it down quickly or there's resistance from the battery positive that's preventing enough current from flowing to the motor.. maybe a loose connection.
If there's and inline fuse we'll look there first if that gives a similar fault.. The cabling runs under the chassis to the battery... is the fuse near the battery or near the new relay? Can't see it there
P
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