Bill B

91 rs 3.1 to 350 carb conversion

is there any reason not to connect gray wire from fuel pump relay
to a fused ignition switched power source
then pitch the relay in trash
i dont see the point in needing a relay the pump dosnt draw that many amps or volts or am i missing something

camaronewbie

Fuel pump does draw quite a bit. And, it's constant, ALWAYS on. I'd keep the relay.

Just connect your fused 12v+ hot-in-run wire to the green/white striped wire on the relay, and keep it.

Yungcris09

Ok camaronewbie here my problem I have power coming from the battery to the fuel pump relay threw the orange wire but power isnt goin nowhere else from the relay to power the fuel pump and I have replaced the fuel pumo relay so I know its good so wat could it be any help would be good thanks

camaronewbie

Power comes in on orange, goes out on grey. black is ground, green/white is power from ECM. ECM gives 12v+ to green/white, which energizes relay and switches power from orange to grey.

I'd look at the connector, make sure the ground is good, etc.

Does relay click when you turn key on? Have someone turn on key while you hold the relay so you can feel it click or not. If no click, then relay not working for whatever reason.

http://www.austinthirdgen.org/index.php?pid=35

Six_Shooter

iTrader: (2)

I would use an oil pressure safety switch in there so that the pump is only on at start and running.

I've seen many times where an engine will get flooded, even hydro-locked from leaving a fuel pump on a non-running engine.

Bill B

Thanks for the responses guys
The reason i asked was because i just installed a tempature adjustable fan relay. an when i finished i checked out the pump relay an noticed that the gray wire that supplies power to the pump is only a 20/22 guage wire.
Which cant supply very much power considering it size an the length of the run all the way back to the tank
but i guess GM put the relay in there for some reason

camaronewbie

You do know that the factory oil pressure sending unit is the one and only reason why a fuel pump will continue to run after the key is turned off, right?

Maybe there's such a gadget as you describe that will disable a fuel pump if there's no oil pressure, but the stock factory oil pressure units we have in our cars have a direct connection to the battery and regardless of the key if it senses oil pressure (or thinks it senses oil pressure) that it will run the pump 24/7 until the battery is dead, even with the key in your pocket.

In my opinion, it's best to take the OPSU totally out of the fuel pump equation, as I've had several bad OPSU's that made my pump run until the battery was dead. And thus I took mine 'out of the loop' so-to-speak. Now, I know if my fuel pump doesn't work it's my relay or my pump, and I never have to fear the pump running without the key on.

ray_riddle

I purchased a 1982 Z28 305 cross fire, The fuel pump was repaced but no gas getting to motor out of injecter, what else should I check? filters changed.

IROCZdude

and just had did you take the OPSU totally out of the equation? and also what does the OPSU harness connector look like ? i cant seem to find it

camaronewbie

OK, I took the two fuel pump wires from the OPSU connector, and ran them to a relay, with a hot-in-run and a ground. So the way I have mine wired now, when you turn on the key, that hot-in-run activates my relay, and connects the two OPSU fuel pump wires to each other, thus making furl pump run anytime key is ON.

I had several times with this car that the OPSU would go bad, either not letting me get any fuel (since I wasn't using the ECM/relay cause I'm carbed now), or making my fuel pump run continuously regardless of the key (since the OPSU fuel pump circuit gets power directly from battery rgardless of the key).

Fot the later years (I think 1988+), the OPSU is a single unit above the oil filter, with a 3 wire connector, the two larger wires being the fuel pump circuit and the smaller one being the wire for the oil gauge.

On earlier cars, there were two Oil senders, one was an actual sender for the guage located on the china wall driver side of distributor with a single wire to it, and the other was an oil switch located above the oil filter, with 2 wires onm it, that activated the fuel pump circuit.

Six_Shooter

iTrader: (2)

You do know you can re-wire the factory OPSU to work as a safety switch, right? No, I'm guessing not, with your reply.

Also there are MANY OPSUs available that work as safeties, in fact, many racing organizations require oil pressure safety switches to control the fuel pumps, in the event of a roll over or crash. Also GM is one of the only (I don't know of any other) company that uses their OPSU to run the pump, and not as a safety.

Also I have never had an OPSU fail as you describe, so it sounds like you either just have some bad luck, or fixed a problem that was actually with a different component.

camaronewbie

Yeah, I know you could rewire it to be a safety switch. And I know that race orgs require them.

I might be THE 'lucky one' that had the OPSU problem - I've yet to hear anyone else have it either. When I bought the car, the battery was dead, and the PO said the fuel pump wouldn't work. Well, the fuel pump didn't work becayse the battry was dead I installed new battery, car sat 2 days, battery was dead. Charged battery, car sat, battery died again. Charged battery 3rd time, and I was out late that night for a walk (couldn't sleep), walked past the car and I could barely hear the whine - was fuel pump, and the key was in the house. I couldn't hear it before with other neighborhood noises during the day. Looked at wiring diags, saw the OPSU, swapped it out ..... Viola! Problem solved.

After that, I decided to take that sucker out of the equation - relays are cheap & easy, I carry a spare now. OPSU requires tools and getting under the car - something I want to avoid on a dark country road.

Yungcris09

Well on mines camaronewbie I have a tan with white a green with white a red wire a black wire and a orange wire on my fuel pump relay and if I jump the orange wire to the green wire the relay will click but not with the key and I just changed my ignition swich to see was that the problem but still no change so wat could I be lookin at to be the problem this tryin to get my fuel pump to come on is bein a headace

camaronewbie

some wiring colors different between years and induction systems.

green/white is signal wire from ECM - ECM gives it 12v+ to activate relay.
black is ground
orange is hot all times
tan/white runs to fuel pump

Green/white wire gets 12v+ from ECM, relay already grounded, so coil in relay activates, switching 12v+ from orange to tan/white.

Yungcris09

What do u mean coil in the activates ??????? Cause I have put 12 volts to the tan and white wire and it has did nothing then I take 12 volt to the green and white wire and still nothing but what do my red wire on my relay do ?

camaronewbie

There's a coil inside the relay - that's how a relay works. It gets 12v+ on one end of the coil, ground on other end, and the coil energizes, making a magnetic field that literally attracts a lever to switch from one connector to another.

You relay works just like I explained. Black wire is ground - put 12v+ where the green/white wire connects, and the relay will energize (you'll feel/hear a click). If it doesn't, then it's bad.

When it "clicks", it's taking power from the orange wire and feeding it to the tan/white wire.

For your use, the red wire is not used - disregard it. It's an extra wire - that runs to a service connector for GM techs, that enables them to "prime" the fuel pump without the ECM.

Yungcris09

Yea when I put 12 volt to the green with white wire the relay do click so I know it works but it still dont send power to my fuel pump when I do that so could my computer be my problem