iroc-si

Hi,

I have an 85 iroc HO that is now fitted with a 200bhp 350 from a 79 camaro. This engine has a holley 4160 carb. As it stands the car has a stock electric pump in the tank, and a stock mechanical pump on the block, with return lines. All fuel lines are -6AN.

I often leave the car for 3-5weeks without using it, and have trouble starting it due to the battery being low and the fuel lines & carb having dried out. This drying out means I have to crank the engine to pull through the fuel, and by the time this has happened I don't have enough power left to start the engine.

What I wish to do is move to an electric only system to alleviate this problem. I know this will probably be noisier but if it works better then I'll be happy.

What I was thinking of doing was to remove the mechanical pump and fitting a carter 4600HP in the engine bay. Putting it there because that is near where I have the mechanical pump at the moment and it would mean altering the fuel lines less. I was not going to use a separate regulator, and thus not use the return lines, but not remove them for now.

Will this setup work, or does the carter pump need to be nearer the tank? I think it would be ok as it also has the pusher pump in the tank.

I would be wiring the carter pump to a oil pressure switch and also to a separate primer switch so I could run it before starting the engine.

Any thoughts on this as a setup?

Simon.

five7kid

iTrader: (14)

Why not just connect the primer switch to the in-tank electric?

(I'm not sure about carb'd engines, but EFI vehicles with the in-tank electric have a timed relay that starts the pump when you turn the ignition to "On", then shuts off after 5-10 seconds. When oil pressure is achieved, the oil pressure switch takes over the power circuit.)

iroc-si

Would you expect the in tank pump to be able to push fuel past a stationary mechanical pump and up into the holley fuel bowls?

I'll see if I can figure out how to do this. Any idea on where I'd find the wire to the in tank pump? Guessing that where a timer relay is would be the place to look. Any clues most welcome...

Si.

five7kid

iTrader: (14)

A mechanical pump is basically a diaphragm with two check valves. Push the fuel in the inlet and it will go straight through the pump.

iroc-si

Hi,

Just an update to say that fitting the primer switch to the in-tank pump relay worked. Thanks!

Interesting discoveries on the way:
# An 85 HO is wired like the 86 in the wiring diagrams above. Colours of wires etc.

# Haynes manual on the subject is very wrong, and the wiring diagrams completely wrong.

# There is no timed relay on this car, the pump runs when cranking and also when there is oil pressure.

Adding this priming switch is also very useful combined with a pressure gauge for troubleshotting a non-starting/bad running car as single handed you can check the fuel is getting to the carb.

Si.

five7kid

iTrader: (14)

Thanks for the update.

There is usually an extra terminal on starter solenoids that provides 12v when the starter is engaged (carry-over from the days of point ignition). Makes sense to run the electric pump power to it, then let the oil pressure switch take over when the engine starts.

That wouldn't work on an FI car, because you need pressure immediately, and the oil pressure may not be high enough when the engine fires to keep the electric pump running - that's why they have a timed relay. But, with a carb, the pump just fills a reservoir, so that issue doesn't exist.