Kjet Fuel Pump Relay

**dub be good to me** · 22-03-2009, 12:27 PM

I'm fitting an 8v Kjet to my Mk1, but don't have a 'tachometric relay' can I just use normal relay?
I have a couple of 30A fused relays lying around, but they only have four pins (missing earth). Will these do?

From my understanding the pins should be (taken from www.diagnostic-assistance.co.uk/mech_inj.htm):
30 - Positive from battery
31 - Earth
1 or 31b - Coil negative
15 - Switched ignition on voltage (from coil)
87 - Out let to fuel pump

What I propose with the relay I have:
30 - Positive from batt
87 - Positive to pump
85 - Switched ignition on voltage (from coil)
86 - Coil negative

Will that work?

**h100vw** · 22-03-2009, 12:55 PM

Would work but you'll get fuel pressure all the time. The extra pin on the std relay cuts off the fuel pump when the engine is stopped.

Getting a prpoer replay should be hard, doesn't have to be a Kjet one AFAIK.

A digifant one would do the same job I think. Or there's Volvos to pillage.

Gavin

**paulie71** · 22-03-2009, 11:00 PM

not a bad idea to avoid anything that doesn't cut off when engine stops. Reason for this is unlikely event of a crash where fuel line is ruptured and pump is still going.

**thestu** · 23-03-2009, 07:45 AM

dude...your wrong.

the big relay controls all the pressure. the small relay is just to control current.

i remember now. the small relay is for the fuel pump (to hold the current) and the big relay is triggered to switch on and off with the coil. when the big relay is triggered it completes the fuel pump relays curcuit allowing the fuel pump to run. only 4 pins on the 30amp relay are used

i told you to call me if you got stuck!

**dub be good to me** · 23-03-2009, 03:33 PM

Don't stress, that post was before I spoke to you yesterday. I wired it up as per your diagram

Still trying to get it started though. I was getting pre-ignition which should be over-advanced timing (and means there is spark?)... so i've been twisting the dizzy clockwise to compensate... expect my battery just died

I'll let you know how it goes. Expect a call