Dual relays for redundancy

[rx7lee]

I wanting to run dual relays for my fuel pump for redundancy. I want to wire one relay to be triggered by the pcm and the other to be triggered by the key. My question is if I run dual relays with a 10g wire and 10g output off each relay meeting at the pump so I'll have two 10g power wires running to the pump and have the relay from the key witched to power and the r delay from the pcm switched to groud and both relays grounded at the same point will the one that comes on with the key back feed the relay off the pcm or will it be fine?

[radiomike]

No, it will work fine as there is no connection between the relay coils and the contacts.  The only downside is that in a crash you could still have the ignition feed powering the pump even though the engine has stopped.

[rx7lee]

Crap good point the will be getting the power from the kill switch so when it's off the won't have power but I see what your saying tell the key or kill switch was turned off it would pump fuel. The iusse with letting the pcm run both is we can't get enough prime time on the 411 pcm to build fuel pressure Cuz the pump and reg don't have a check ball

[radiomike]

You could still do it with a second relay but use a spring loaded switch not the ignition.

[digitalsolo]

I ran a fuel system with no check valve and a 2 second prime and had no issues?    I'd let the PCM control it personally.   

[rx7lee]

Then there must be iusse with my fuel system I have a 10-15sec prime time and it still takes 3-5 trys to get it to build fuel pressure and start I don't doubt that I have a iusse I just have no idea what to look for or how to fix it

[digitalsolo]

Interesting.   What is the setup?

[rx7lee]

Magnafuel 4303 and magnafuel regulator All an lines.fast fuel rail 80lb deatschwerks injectors -8 tank vent.-12an outlet on the sumped oe tank . No fuel leaks

[digitalsolo]

Hmm.   That's pretty similar to BeasTTs and my own setup.   Same pump, similar regulator, etc.    Both of us ran a 2 second prime and no check valve and it fired at the touch of the key.

If you hot wire the pump to run constantly does it start right up?

[rx7lee]

Yea that's the weird thing if it's hard wired or once I get fuel pressure it starts right up it starts as fast as my stock Silverado once I get the fuel pressure. Yea I thought you guys ran close to the same fuel setup I'm not sure what the iusse is with my car other then I built it lol id say the guy who tunes it is ok maybe not as good as the guy that tuned your guys stuff but the afr is good once it's running

[Cobranut]

Is your fuel pump above the level of the tank?
Sounds like it's losing prime, and running the pump dry until it picks up fuel again.  Not good for the pump either.

[rx7lee]

Fuel pump is below the tank and the tank is sumped

[rx7lee]

Would a 1N5402 diode work to keep the relays from back feeding each other?