Fuel Pump relay clicking open and shut

[adyw]

Does anybody have any ideas why all of a sudden whilst driving the fuel pump relay on occasions clicks quickly open and shut again.

Initially I thought dodgy earth, so I put a new wire to the after market ecu I have fitted. No change

New relay fitted, No change
Drove round with a mate in the passenger seat with a volt meter connected to ignition 12v feed into the relay, just in case there was a fault with the 12v switch feed, No change 13V + all the time.

The relay does not do it at the same revs or whilst accelerating only, it is random.

Any ideas

[chrispitman]

I thought that in the std setup the power to the relay is from the alarm, so there could be a problem with the alarm module. You could try swapping this for a battery fused live to see if the problem dissapears.

[spend]

Immob & Inertia should be between relay & pump. Replace the relay with your 'spare' as a first step

[GreenV8S]

adyw said:

Does anybody have any ideas why all of a sudden whilst driving the fuel pump relay on occasions clicks quickly open and shut again.

If the relay is mechanically opening as your description implies, then the coil circuit is being disrupted. You need to investigate to see whether the 12V supply is dipping, or the earth (via the ECU) is failing. If you measure these at the relay socket you must also consider the possibility of a faulty connection between the socket and the relay.

[Bluebottle]

Are you sure its the pump relay/s on the loom switching rapidly and not the radiator fan relay on the fuse board?

I have had this symptom twice now, both due to faulty otter switches.

Edited by Bluebottle on Monday 27th October 13:42

[Mark Adams]

Whilst I can't comment on your installation since I don't know the details, most good ECUs will switch off the fuel pump if the crank trigger signal dissapears as a safety measure. Therefore it may be a good idea to start with monitoring the crank trigger (with a storage oscilloscope) and get a trace for that.

[adyw]

Thanks, gents,
some ideas there, I will do a re rig of the relay on saturday and go for a drive and see what happens,
It is the fuel pump relay as when it kept clicking in the garage I was able to hold the relay and feel it clicking open and shut,
What I might do is to record a run on the old laptop plugged into the new ecu and see if the fuel pressure drops off at any time specific compare to something elce.
If not we are still in loose connection land.