HottestZ28

I want to wire in my electric fuel pump to run with the key on. I did a 350 carb'd swap and no longer am using the CPU. I want it safe and reliable

what would be the best way to wire this?

Car 1987 2.8 camaro => carb'd 350

irishhockey34

iTrader: (12)

You MUST use a relay. The relay itself will need:

- +12v (constant from battery)
- (-)Ground
- +12v (ignition)
- +12v (output to fuel pump)

The +12v ignition will be used as the trigger to allow the fuel pump to receive +12v when the key is only in the ON position

HottestZ28

where do i get this relay and how do I actually wire it to the fuel pump? can I use existing wires that went to the original relay? then just add a key on lead

CamaroRider

If you still have the factory installed fuel pump relay 'connector' that originally went to the fuel pump relay that would be a good choice (for convenience).

The relay can be purchased at an auto parts store. It is the 'fuel pump relay' for that year and make of automobile.

The more difficult part would be in actuating the fuel pump relay properly.

The ECM controlled the fuel pump relay in such a way that when you turn the key from OFF to RUN the fuel pump relay would be energized for only 2 seconds to 'prime' the fuel line (fill it and pressurize it). When the ignition key is changed from RUN to CRANK and the ECM detected that the distributor was spinning the fuel pump would be powered on constantly. If the engine continued to run (and the distributor was spinning) when the ignition key was allowed to fall back into the RUN position then the ECM would continue to power the fuel pump relay.

However, if the ECM detected that the engine did NOT continue to function properly when the key was in the RUN position the ECM would turn the fuel pump relay OFF.

So you see the ECM did some decision making as to when to turn the pump on and off.

The fuel pump relay is actuated by supplying a small amount of power to the actuating wire. But as you see above the ECM is normally in control of that wire and it makes some decisions as to when it should and when it should NOT be actuating the relay. If you simply hooked that control wire up to a fuse that was on only in the RUN mode then it might be OFF in the CRANK mode. If you hooked the control wire to a fuse that was only active in the CRANK mode then it might be OFF in the RUN mode. In any case the decision making performed by the ECM would never be present. That is what would make it tricky to set up without the ECM involved.

HottestZ28

I do have the relay and connector and wiring harness
good information from above, Ok if I were to wire it to a "run" only power source being it's carb will there be enough fuel in the bowls to get it started on crank then when it's on run the pump turns on.
or can you run 2 different signal power wires one for crank one for run?

CamaroRider

Well you could give it a try. I have not done anything along this line because I have a TBI system with the ECM. But what you do NOT want is to be 'out in the bush' and find the car just will not start !!

You can experiment. The fuel pump relay on my car uses the DARK GREEN/WHITE wire (which I believe is the middle wire of the five on the connector) to actuate the fuel pump relay. It normally runs to the ECM so it is available inside the car where the ECM had been. On my car this would have gone to connector A1 on the ECM harness connector. That wire should (probably, eventually) have some type of fuse installed in case you short it to ground. I do not know what to suggest as an appropriate fuse but it probably will be something like .75 Amps (just a wild guess). If you feed it with +12 volts the relay should actuate. You might be able to hear it actuate or feel it actuate if the cover cannot be removed to see the contacts move. I guess you should start with that simple test to see if you can actuate the relay with jumper. If you cannot actuate the relay then there might be a fuse that needs to be checked or maybe wires need to be traced to find out what is going on. Once you can actuate the relay in a test mode you can move on to a more permanent installation (to make it protected and fool proof).

If you are going to give this a try let me know and I can give you more details about the wires that exist in the fuel pump relay connector.

It might be that if you actuate the relay you will immediately hear the fuel pump turn on so pay some attention to the sound from the fuel tank area.

I guess one concern is that the excess fuel that the pump supplies needs to be returned to the tank. This might require an external fuel pressure regulator if your present system does not have a working 'return to fuel tank' line for any excess fuel.

CamaroRider

Your question about hooking the actuating wire to two fuses, one that is on when in the CRANK mode and one that is active in the RUN mode is NOT (repeat: NOT) something you should do without thinking through the consequences. If you had properly placed DIODES you might be able to 'rig' something up. You should NOT (repeat: NOT) run simple wire connections between a CRANK related fuse, a RUN related fuse and the RELAY trigger wire because that would send power to the CRANK circuit and the RUN circuit (both) when any ONE of those fuses sent power to the RELAY. Properly installed DIODES could 'direct' the voltage so that there should be no problem. So do not experiment in this area before you have a solid grasp of the consequences.

HP52TA

iTrader: (4)

If you want to play it safe you should also install an oil pressure safety switch. I think this may be where you are getting the dual path of wiring idea for your fuel pump relay. It is actually a single wire connection to the relay but has alternate power paths through the oil pressure switch, based on its state.

Take a look at page 5 of this link...it should help. I am moving to a carb from TPI and will be going this route myself.
http://www.holley.com/data/Products/...199R7914-3.pdf

When cranking your starter, power from the starter energizes your fuel pump relay to provide fuel to the carb while zero oil pressure is present, once the engine has started and oil pressure builds the electrical path through the oil pressure switch changes state. (starter now de-energized) Should you lose oil pressure while running it deenergizes your fuel pump and could save your engine from damage.

As Camarorider said you can reuse your existing fuel relay if it is still there and the Dark Green / White wire is where power is applied to energize the relay.

If you are running the stock fuel pump you will need a regulator to decrease the pressure to the carb. A bypass regulator with a return to the tank is best.

HottestZ28

I have the factory relay but the wiring is sitting in a box, because of going to carb. I took out the whole harness and simplified it to run only to the starter, choke, fan high speed.

Now I just to get the engine to run used a wire to the brown lead (16ga) to the fuel pump. It started and everything checks out that way.(found major leak out the front main seal, brand new oil pan and proform cast aluminum timing cover, felpro gaskets)not sure what thats about?

I am running an autometer oil pressure gauge, and might go with the oil pressure switch but not sure i want to over complicate it right now

With the relay it has 5 wires but seems to only have 4 terminals and runs 2 green wires in one terminal(like 16ga wire)-then 2 (12ga) wires 1 black 1 red and another wire(16ga) that I can't remember what color it was. I need to completely rewire it but not entirely sure how to.

ok so now if the wire going to the fuel pump was on 16ga why is there a need for a relay

CamaroRider

I think the original purpose of the relay was to allow the ECM circuit to use its rather low current circuit to control the switching of the relay on and off. Then the relay could, in turn, switches on and off the larger current needed by the fuel pump motor. In that way the ECM would not have to handle any kind of spikes that might take place when the fuel pump motor is initially energized and eventually de-energized (the relay contacts would be robust enough to handle those transition points).

The relay also allowed one of the ALDL connectors to be used to power the fuel pump relay when the relay was OFF. When the relay was ON the ALDL connector was NOT available to feed power to the fuel pump. In your case I do not think this function would need to be of interest.

I hope you observe the suggestions to use some type of fuel pressure regulator and return hose (to the fuel tank) as mentioned above. I suspect that if a regulator is not used then you will eventually damage some part of the carburetor with excessive fuel pressure applied and it would also likely cause the fuel pump to overwork, generate too much heat and eventually fail.

There are other posts that discuss changing a carburetor system to use a fuel pump so you should read those and proceed with confidence. They might discuss using or not using the original fuel pump relay. If you are not familiar with the workings of a relay as used in this application it probably will not take you long at all to catch on and install one successfully.

HottestZ28

Yea I am running a Mallory 4309 3 pot with return. I have it installed using factory lines I custom bent and 45* flared to unions which seems to work very well so far.
Yea I'll have to research alittle more, it seems everytime I search I never seem to find what I am looking for.

HP52TA

iTrader: (4)

Check out the sticky at the top of this forum by regal1975. There are links to autozone where you will be able to find a wiring diagram of your specific vehicle.

HottestZ28

ok this weekend I wired in the factory relay
Large Red- used wiring from car to run to the junction box next to the battery with the factory fuseable link
Black/red- Ground to factory ground on firewall
Green/white- actually had 2 wires in the same cavity. These ran to the oil sender and another ran to the ECM
Tan/white- Ran to the ecm but was solderd to another tan/white that IDK where it went
Tan wire to the fuel pump wiring because it was Tan as well
ran the green/white to ground first-nothing
then ran it to a fuse for power and almost popped the fuseable link
then reversed it made the tan ground and then power and had the same result from the fuseable link actually it "jumped"
any thoughts?
I know I can buy a relay but if this one will work I would love it

kennn

I don't know if anyone thought about it but what fuel pressure is your pump putting out, and what fuel pressure does your carb want to see?


I got rid of my electric in-tank pump and used an Edelbrock mechanical fuel pump in my carbed 350.

HottestZ28

I'm running a mallory 3 port adjustable regulator