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My thoughts on the switch....It closes at higher temp to raise the fuel pressure.The idea being that there will be less likelihood of vapor lock with higher fuel pressure when crawling in 4wd.Higher fuel pressure will also lower the AF ratio which also would have a cooling effect on the engine.Then finally, I know that an 86 came with a 1-wire O2 sensor. So it's possible that at idle speed the engine reverts to open-loop mode and the ECU won't correct for the slightly richer mixture. (I had an idle problem when that happened and retro-fitted a heated O2 sensor to fix the idle (which might mean this switch won't do anything on my engine because the ECU always has an O2 signal (or the ECU goes to open-loop anyway ))) Then if that's true, does the ECU only raise fuel pressure if you're in 4WD.......
The fuel pressure regulator has a vacuum reference on it.More vacuum, less fuel pressure. (So at WOT, you get more fuel pressure)There's a vacuum bleed off solenoid. The ECU would trigger the bleed off solenoid. Then the fuel pressure regulator would raise the pressure like it does at WOT (even though it's not at WOT)With 4wd, you don't get as much airflow in the engine compartment and can get more heat buildup.
It's a return style system.I think you might be wrong still on what the coolant temp switch does.Look into a/c coolant temp cut switch and you might find the answers.
Gear ratio calculations…4th gear 1:1 – 31” tires, 4:10 ring & pinion – at 79 MPH (my freeway speed) = 3862 RPMs5th gear 0.8:1 – 31” tires, 4:10 ring & pinion – at 79 MPH (my freeway speed) = 2809 RPMsGear ratio calculations… 4th gear 1:1 – 31” tires, 4:56 ring & pinion – at 79 MPH (my freeway speed) = 4396 RPMs5th gear 0.8:1 – 31” tires, 4:56 ring & pinion – at 79 MPH (my freeway speed) = 3124 RPMsThe peak torque “sweet spot” with this engine rebuild (261C cam+DT header), according to my desktop dyno, is between 3100 to 3300 RPMs (it may be different on the street and when chassis dyno’d) As Snowtoy pointed out, his butt dyno likes the snappy lower gear ratio. I may end up spending the money to swap in 4:56 ring & pinions.Gnarls.
Time for a remedial math class..... 3862 * .8 = 30904396 * .8 = 35173862 * 4.56 / 4.10 = 4295Are you at least sure about the 3862 ?
Question on the gasket for the throttle body to intake.....Do you use any sealant or gasket goop, or just go with the bare gasket?Thanks,Gnarls.
I made some good progress today. I thought I had all the wires, connectors, and hoses accounted for, THEN I found this! It comes out of the main harness.I don’t have any idea where it goes - IF it was connected to something.The inside of the contacts looks like it was NOT connected to anything.Does anyone know what this wire is for?Thanks, Gnarls.
Final info that I could find on a previous subject.If you ever see this book for sale, buy it eminently. It was given to me by a long time Chevron tech about 10 years ago when He retired. Theory and operation of 80's fuel injection systems. Knowledge that is lost forever.
It is the one of those LFRE connectors that all Toyota's have.
LFRE...?? Left For Rebuilder's Enjoyment???Gnarls.
I took a look at mine for you tonight. I have one connector in that area that goes to nothing. It is a two pin connector. I believe the one I have is for the addition of A/C. The only one I found that has a connector likeyours goes to the temp gauge sender. The wire color is Yellow with a green stripe for the temp sensor on Mine.Hope that helps you.
Fuel return hose.The one on the diaphragm is a vacuum line. Should connect to a VSV before manifold vacuum. (remember the discussion on the mystery 4wd thermal switch......)
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