I’d think 2mm or 2.5mm2 is fine for the pump. Assume it take 5 - 10A (probably an overestimate). Also 2mm2 for the pump earth. 1mm2 is fine to drive the relay coil. No real need to have a hot start relay with 9mm terminals on. A boggo 40A (even 30A) job will do. Halfords will sell you one.
Great, I'll up the earth as suggested and buy some big female spades connectors as the relay I have has the 9mm spades. Thanks
The pump relay is all wired up and nothing....I've tested the relay and it's a duff one, so I've sent a note to AutoDoc and we shall see what they say. I checked the relay with a multimeter and the switch is remaining open. If 12v is put across the switch #1 and #15 the switch does not activate and using the multimeter on ohms the reading stays at 1 and does not change when powered.
Not sure what you mean by 1 and 15 on the relay. Stick 12V across 86 (+ve) and 85 with other stuff disconnected. The relay should click. Disconnect stuff before measuring resistance, or the meter will get confused.
The relay is as follows (photo attached ):- 15 Coil + 30 Fuel Pump +ve 31 Ground- 1 Coil -ve 87 +12v @snotty, I disconnected everything and put 12v across the two coil trigger connections (1&15) assuming this would create the click. Happy to be wrong...if it saves returning this!
Ah, it’s a fancy coil-triggered job. 30 - +12 pump supply (fused) 87 - pump +ve (pump -ve to ground) 31 - relay ground (skinny) 15 - ignition-switched +12 1 - coil “1” The relay won’t trigger unless an ignition coil is connected or engine running. The relay relies on a hefty back-emf (voltage) from the coil to operate. 12V on “1” won’t trigger it. Hth.
As an explanation: putting +12 across 1 and 15 won’t make it operate. It’s not a normal “dumb” relay - there’s a bit of electronics inside to do the triggering stuff (which needs a ground on 31). Even then, it won’t trigger off 12v - it’s designed not to. Needs about 35 to 60V on “1” to come to life.
Thanks. When it was connected up, via the coil and battery as you mention, the engine seemed to cut out. As the only change I made was the relay, I guessed a lack of fuel. Wiring the pump back to the coil directly all was well. So if I've tested incorrectly I'll refit and try again. Just to check one thing you mention. 87 goes from relay to pump +ve. The pump is obviously earthed. Is that what you meant?
Try again . The fancy relays do work. Quite hard to damage it. 87 is the switched +12 output to the pump. The other side of the “switch” is 30. Which relay did you get from Autodoc?
Tried again and same result, the engine dies after a bit, whereas with the old wired directly it ran normally. The relay is this one below and I've even tried swapping 87 and 30. Dies each time.
I might be taking a trip to Halfords soon. @snotty, off the 3 or 4 Halford relays that have 5 pins, which one should I buy if I can't figure this one out?
Don’t panic. I’ll do a fag packet pic when I get back home. What you’ve got should work. If you are getting a boggo relay as a fallback, a 4-terminal 30A job should work for the pump.
Thanks Here is my fag packet....Edited because I'm an idiot.....swapped 87 and 30 on drawing, but I have tried connecting these both ways
Here you go. Same as yours! As above, the relay won't trigger unless connected to a (switching) ignition coil.
I'm puzzled then what to do other than returning it. With this set up, would you expect the pump to prime when I turn the ignition on only? That would be a good test. Currently no sound. I can hear the pump with the old set up (pump +ve direct to coil). Any other tests or it's on it's way back to Germany. Thanks as ever
