I just installed a pair of Holley "Black" electric fuel pumps and one died within 5 minutes run time. Good thing I was watching the fuel pressure guage because it just dropped like a rock.

I checked power to the pump with a test light and it was getting juice but did not work at all. It was a bit hot to the touch.

Since I just did a temp hook up, I got my key-on power from the purple wire on the positive side of the coil. It did start to work again after a few minutes but I don't trust it now.

Is taking key-on power from the coil a no-no?

Thanks,
Kurt

well if it is too close to the spark plug terminal where it could jump spark to it then this could explain why it went dead.

Roby

BIG, HUGE, HONKING NO-NO!!!!!!!!


If you checked the actual volts at the coil/pump connections you would find something near 5-8 volts. This puts a strain on both the coil and the pump. They must be fed independently and I would recommend a suitable relay to power the pump-rated at least 10 AMPS. And yeah, the new pump is likely trashed.

Biggus-- Insptech is right on. Don't ever do that.--Lou

Install a Tee on the oil pressure sender and put a Normally Open pressure switch on it. Feed 12V to one side and send the other side to a relay that is powered from the battery or battery switch. When the oil pressure hits the close pressure on the switch of about 10 pounds it will send 12V to the relay and cause it to close feeding power to your pumps. The relay for the pressure switch should be rated at 30 amps and the pressure switch maybe 5 or 10 amps. The relay will only draw less than an amp if that. The pressure switch normally will not handle the amps the fuel pump will draw, that is why you feed the relay with it rather than the pump directly. If you need to prime the carb just jumper the pressure switch closed for a few seconds. Merc sells a pressure switch and the relay can be bought at Napa or Radio Shack. Mount two of them adjacent to one another for each pump, if one fails just move the terminals to your spare.

Bad Dog's setup is good BUT.
You also gotta jump to the starter circuit for auto priming. Otherwise, you gotta remember to prime.

SPDT relay.
Center post to fuel pump (appropriately fused for pump).
N/O post to starter solenoid output.
N/C post to 12v bus (30A fused).
One side of relay coil to ignition "run" position (ignition coil 12v+).
Other side of relay coil to oil pressure switch (N/C 10psi oil pressure switch).

When ignition switch moves to ON position, low oil pressure allows ground path to be complete to close the relay. With relay closed, fuel pump can only receive power when ignition switch is in the START position (solenoid energized). After oil pressure rises, relay drops open, passing current from 12v bus to pump.

If engine stalls, oil pressure drops, pump stops.

It's also extra good sense to have an accessible pump master switch that kills juice to the entire pump circuit in the event of some malfunction.

Hey Kurt, I think the circuit diagram for what mcollinstn said is in the Holley instructions. Did you install something without reading the manual?

If i dont use the oil pres switch i just cant leave the key on correct?

i just want to use a relay that is siwthched by the coil volatage and supplies the fuel pump with power directly from battery. will this be ok

Definately add a relay ! All the fuel injected motors I've ever seen with an electric pump all have relays.
I have some if you need them . I parted out many cars in the past and I could give you a bunch of Bosch relays.
Thanks for stopping by and dropping off the hats.
Kurt's da man !