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TBI to PF4….wiring
- Thread starter JT88K5
- Start date
@Bent77 Thanks for posting that pic. Your install looks clean.
@mrk5 , regarding the heavy pink vs pink/blk wire. It looks like both are ignition in the diagram. I was going to use the pink/blk since it was closer in size to the pf4 ignition wire (also pink/blk). Seems either wire should work correct?
@mrk5 , regarding the heavy pink vs pink/blk wire. It looks like both are ignition in the diagram. I was going to use the pink/blk since it was closer in size to the pf4 ignition wire (also pink/blk). Seems either wire should work correct?
I think so. I always double check with the VoM or test light
I washed under the hood of the truck, I’ll get a picture here in just a bit
Yes, I've used both
Right now I'm using one to power efi on and the other powers on the trans controller.
If or when the 700r4 gives up, I’ll likely convert to an electronic controlled tranny and will need a second ignition wire.
Just to get cold clean air, less any water, I was thinking about using the stock air cleaner with the hose going to the core support vs open like on the car. In looking around for alternatives, I didn’t see any like you have on the truck pic, where the air cleaner was still on top of the intake. Do you feel you have enough filter surface?
Just to get cold clean air, less any water, I was thinking about using the stock air cleaner with the hose going to the core support vs open like on the car. In looking around for alternatives, I didn’t see any like you have on the truck pic, where the air cleaner was still on top of the intake. Do you feel you have enough filter surface?
2 things
The pf4 doesn’t have an internal transmission control. You’ll need an external
I’m running a 2.5” TBI riser below the air cleaner into the intake. Using a 4” filter with 2x 4” tubes running into the core support
I have a batwing air cleaner.
Thinking ahead, because I’m not done wiring yet, but hope to get it wrapped up this weekend.. I might not be good, but I’m slow.
I need to talk about vacuum lines. My help pulled all that shit out before I had a chance to take some pics and notes.
I have the vacuum bulb thing (dr side on top of inner fender at firewall), plus the brake booster vacuum and the heat/vent comtrols, that’s seems fairly straight forward. I have a canister just to the right of the radiator, standing in front, that looks like it had a vacuum line on it. The canister has another hard line that looks like it goes back to the gas tank. What do I do with that? No smog pump anymore. If I get ride of the canister, can I just pinch the hard line?
just dawned on me to look for a vacuum diagram. I’ll do that but any input on the canister thing would be appreciated.
I need to talk about vacuum lines. My help pulled all that shit out before I had a chance to take some pics and notes.
I have the vacuum bulb thing (dr side on top of inner fender at firewall), plus the brake booster vacuum and the heat/vent comtrols, that’s seems fairly straight forward. I have a canister just to the right of the radiator, standing in front, that looks like it had a vacuum line on it. The canister has another hard line that looks like it goes back to the gas tank. What do I do with that? No smog pump anymore. If I get ride of the canister, can I just pinch the hard line?
just dawned on me to look for a vacuum diagram. I’ll do that but any input on the canister thing would be appreciated.
that canister is your tank vent. If you run a vac hose from it to a ported vacuum source it will draw any collected fuel vapor. If you remove it you'll need to figure out a vent for your gas tank.
Thanks. Did the smog pump provide the ported vacuum? I see both vacuum connections on the PF4 are “Not for fuel”. Do I need to source a 12v vacuum pump. I have a smaller hose that runs along the fill hose up to the gas cap, I always thought that was a vent.
That is the fill vent. No the air pump didn't provide the vacuum fir canister. It may have shared a thermal vacuum switch though.
You really shouldn't get any wet gas from the canister, only vapors, so I think the pf4 vacuum ports would work, but need to be ported, ir before the throttle plates.
You really shouldn't get any wet gas from the canister, only vapors, so I think the pf4 vacuum ports would work, but need to be ported, ir before the throttle plates.
I haven't connected my charcoal canister, (tank vent) to my PF4 yet because I had issues with other external parts previously. I plan on trying to hook it back up in the future as I got reminded again this weekend of the fumes that can occur with the line just hanging up by the firewall. 
I’m stuck on this charcoal canister vacuum source. As someone stated there is no ported vacuum on the pf4. No port in the water chamber to add a thermal activated ported vacuum switch.
The consensus, and as Wes noted, seems to be that vacuum before the throttle plate is considered to be ported. Seems to me this could be accomplished by adding a spacer between the throttle body and air cleaner and stick the vacuum line in the spacer. Or by simply tapping into the bottom of the air cleaner assembly, similar to mounting the air temp sensor for the pf4. This seems too easy to work. It also seems like someone would have already suggested this in one the many posts I’ve read on multiple forums.
I understand it might not be optimal. From what I’ve read the vacuum to the canister is only open until the engine warms up.
The consensus, and as Wes noted, seems to be that vacuum before the throttle plate is considered to be ported. Seems to me this could be accomplished by adding a spacer between the throttle body and air cleaner and stick the vacuum line in the spacer. Or by simply tapping into the bottom of the air cleaner assembly, similar to mounting the air temp sensor for the pf4. This seems too easy to work. It also seems like someone would have already suggested this in one the many posts I’ve read on multiple forums.
I understand it might not be optimal. From what I’ve read the vacuum to the canister is only open until the engine warms up.
any where above the throttle will do it's not a critical vacuum signal you just want to get the fumes out of the canister.
I suspect the concern is if the EVAP cannister isn't "sealed" when the truck sits (via an Evap valve, etc) you could potentially have fuel vapor accumulating under hood which is clearly not an ideal situation.
I don't think running it into the air cleaner would be a problem besides the above concern. If using ducted air from outside the truck and you trust the seals in that system, I'd probably think dumping it straight into the intake tract/air cleaner to be low risk.
At one point didn't GM use some sort of bi-metallic thermal vacuum cutoff on the bottom of the air cleaner for something like the choke? Can't remember what it was for, but I recall that it was "clean" (behind the air filter) air. Thermac. It was for thermac.
@dyeager535 , from what I can tell, the ported vacuum switch, is thermally operated. In the old tbi motor, the intake had a spot for it that went into the coolant channel. No port on new intake for it.
Last wires I have to connect go to the trans. I found a post in another forum and a fellow was talking about the trans tcc connection. He was converting a 87 tbi, like mine, to a carburator . the crude diagram below. I was laying out the wiring from what was directed in the post. First diagram was reading and drawing lines, then I looked at it and laughed. 2nd drawing was what I think he meant. @Bent77 , you mentioned I only needed the vacuum switch, I think it was mentioned to put it in line with the brake sw wire. Any thoughts?
Last wires I have to connect go to the trans. I found a post in another forum and a fellow was talking about the trans tcc connection. He was converting a 87 tbi, like mine, to a carburator . the crude diagram below. I was laying out the wiring from what was directed in the post. First diagram was reading and drawing lines, then I looked at it and laughed. 2nd drawing was what I think he meant. @Bent77 , you mentioned I only needed the vacuum switch, I think it was mentioned to put it in line with the brake sw wire. Any thoughts?
The point of in line with the brake switch so that it will unlock the TC
I dont hate the idea, but also didn’t think it was necessary when I had the vacuum switch set up on my Camaro.
Pretty easy to change if you try one way and want to see how the other works
I dont hate the idea, but also didn’t think it was necessary when I had the vacuum switch set up on my Camaro.
Pretty easy to change if you try one way and want to see how the other works
