Cascade Crew

91camaro_rs · Posted: Sat May 10, 2014 11:27 am Post subject: tbi to carb help

Okay so im helping convert a 91 tbi 350 to carb. I seperated all the ecm wires from guage wires but there are 3 things I cant figure out.

1. Oil pressure wiring. Orange brown and gray I believe only the gray one goes to guage. What do I do with the other two?

2. Fuel pump and relay. Using stock pump with aftermarket regulator. Theres 5 or so wires coming out of that relay/plug how should I run the rest of the wires that would have went to ecm? Or should I just wire the pump to ignition 12v so pump comes on that way...

3. Torque converter lockup plug...I have no idea what to do with

Thanks in advance!

Quasi-Traction · Posted: Sat May 10, 2014 6:41 pm Post subject: Re: tbi to carb help

Al Hasse · Posted: Sat May 10, 2014 7:54 pm Post subject:

When the fuel pump relay fails, the switch in the oil pressure sending unit will energize the fuel pump when oil pressure builds up. I went through three of those 3 wire units at Auto Zone because they were wired backward and turned on my fuel pump as soon as I plugged them in, finally went to NAPA and got one that works.

aaron_sK · Posted: Sat May 10, 2014 8:32 pm Post subject:

Do not run an electric fuel pump into a carb without an oil pressure kill.

The factory GM unit is a trigger, not a kill.

Proper way to do it is to get a oil pressure switch that closes at a low PSI and use it to ground out the pump relay.

You will need a vacuum lockup control for the 700.

It's problems like this that are god's way of telling you that what you're doing is dumb and wrong. Razz

Xophertony · Posted: Sat May 10, 2014 9:45 pm Post subject:

Why would you not want to run an electric fuel pump on a carb without an oil pressure kill?

chevymad · Posted: Sat May 10, 2014 9:50 pm Post subject:

There's nothing to shut off the pump in a rollover.

Xophertony · Posted: Sun May 11, 2014 6:37 am Post subject:

Ah, thanks. So what shuts off fuel in a rollover on my TPI?

Alphius · Posted: Sun May 11, 2014 6:57 am Post subject:

When the engine dies the ECM turns the fuel pump turns off 2 seconds later.

chevymad · Posted: Sun May 11, 2014 8:50 am Post subject:

Also with efi the injectors don't fire when the engine is not running. So there's no fuel spilling. With a carb unless you are exactly upside down, the float won't close and if the pump is runniing it will be pumping fuel out til the tank runs dry.

Twilightoptics · Posted: Sun May 11, 2014 8:56 am Post subject:

Mazda wired my fuel pump with carb, key on only. Just saying.
If the float boel is empty enjoy that long crank time while oil pressure builds. Enjoy finding a key on and starter engauged power circuit.

The pump needs to be on a relay. Not wired to ign power.

IIrc the tan wire goes to the oil pressure gauge.

chevymad · Posted: Sun May 11, 2014 9:12 am Post subject:

Just saying the reasoning. But my electric pump in the 74 isn't wired that way either. Guess i'm betting the odds it won't roll over.

aaron_sK · Posted: Sun May 11, 2014 9:22 am Post subject:

chevymad · Posted: Sun May 11, 2014 9:40 am Post subject:

If your regulator is set right you won't flood it. Most of the bosch flappy door injection setups use it to turn on the pump. I know toyota is that way as well.

Twilightoptics · Posted: Sun May 11, 2014 9:55 am Post subject:

They ran everything through the ign switch lol.

91camaro_rs · Posted: Sun May 11, 2014 2:42 pm Post subject:

So do I run the two extra wires off the pressure switch to fuel pump relay? And what kind of vacuum swotch for the lockup?

Al Hasse · Posted: Sun May 11, 2014 6:26 pm Post subject:

Looking at a couple of wiring diagrams on Austin 3rd Gen, the tan wire goes to your gauge. The other two go to the fuel pump relay, the gray one on the ECM side (diagram doesn't indicate pin numbers/letters) and the orange one to the gauges fuse side.

Twilightoptics · Posted: Sun May 11, 2014 6:29 pm Post subject:

TCI used to make a pretty good lockup setup.

83Z28BlackBetty · Posted: Mon May 12, 2014 10:09 am Post subject:

TCI makes a kit for the lock up, but its pretty easy to DIY if you can find the right pressrue switch. You need a vacuum adjustible pressure switch, run it to a vacuum line off the intake, and wire it in to the trans. So when in 4th gear (the 4th gear solenoid will close its circuit) and high vacuum aka low throttle pressure, cruising, (the vacuum switch will close its circuit) and it will activate the lockup on your trans. If not you will burn through a 700R4 in a hurry. Ask me how i know, I used to have a converted carbed 305... If you have quiestions let me know. ALso you can always ditch the electric fuel pump all together and bolt on a mechanical pump. They are like $20 and no wiring required.

~JAKE

Twilightoptics · Posted: Mon May 12, 2014 1:10 pm Post subject:

Jake you cant bolt a fuel pump into his engine. Tbi blocks are one oiece rear main blocks which dont have a hole for the fuel pump. Plus the fuel injected oe cams dont have a fuel pump drive lobe.

Alphius · Posted: Mon May 12, 2014 4:34 pm Post subject:

I bolted a manual fuel pump up to an '87 TPI 1-piece RMS block with the stock cam and it worked fine. Maybe they got rid of the fuel pump lobe by '91 though. Just wanted to prove Paul wrong. Laughing