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R33 (s2) Afm Into R32 (s1) Grounding Question

Paulusc44
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Paulusc44 Enthusiast

Paulusc44

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Have searched, info is varied.

Have removed plug from loom etc, and have info off internet on basic wiring inputs for R33 S2 AFM and R32 RB20DET AFM.

R32 AFM has 4 inputs/pins

R33 AFM has 3 inputs/pins

I know where to put the (12v) power and (5v) signal wires, but on the R32 loom there is both an earth for chassis and earth for signal, and we have only 1 pin left on the R33 AFM? one to chassis and one to AFM im thinking??

Whats the go here?

Cheers :)

Paulusc44 Enthusiast

Paulusc44

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Ground is ground.

Not when your working with a 5 Volt reference signal.. The Grounding should technically happen across the AFM not the chassis. This is where my confusion began haha might just try and sort it myself with a multimeter and see what I come up with

Paulusc44 Enthusiast

Paulusc44

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It all ends up at the same ground at the ECU. Ground is ground. Zero volts. You don't actually think that the 5V is relative to another completely isolated ground do you?

So judging by what your simply saying here I can join my 2 earths (signal + chassis) and then route them to the R33 S2 "earth" pin? Im fully aware what a 5 volt reference signal does, and on alot of later model vehicles a 3 pin MAF or MAP is far more common, which leads me to believe I can simply join them? Im just double checking

Edited by Paulusc44
Paulusc44 Enthusiast

Paulusc44

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Haha Just went to fire up the thing, have done an entire range of mods over the last 6 months without starting it up.. no puel pump? Ive got 12+ volts at the + pump wire? Im thinking ign. signal? Is there a way to by-pass this directly from the battery to check? Fuel pump is a 12 month old Walbro 255LPH

GTSBoy Grand Master

GTSBoy

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Well, like pretty much anything else in a car, the circuit is switched on the earth side. Having 12V there is a good start, but you need to see whether you're getting the other side going to ground when the pump should be on. The whole lot is controlled by the ECU, and there is a fuel pump relay and module interposed between the ECU and the actual big current flow through the pump. They are a known weak point for failure in general, and obviously the likely place to look.

You just need the wiring diagrams from the R32 GTR workshop manual pdf. The RB20 engine stuff is in there too, because the same manual covers the GTS4.

Paulusc44 Enthusiast

Paulusc44

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Well, like pretty much anything else in a car, the circuit is switched on the earth side. Having 12V there is a good start, but you need to see whether you're getting the other side going to ground when the pump should be on. The whole lot is controlled by the ECU, and there is a fuel pump relay and module interposed between the ECU and the actual big current flow through the pump. They are a known weak point for failure in general, and obviously the likely place to look.

You just need the wiring diagrams from the R32 GTR workshop manual pdf. The RB20 engine stuff is in there too, because the same manual covers the GTS4.

Yeah man was pretty much at that point of things, was wondering if I could by pass the 4 pin relay control circuit for the signal? This would effectively run the pump the entire time I know but its saves me a semi-dodgy bench test? (as fuel pumps can be) Like, feeding signal and power directly from the battery and then earthing the pump directly on the chassis? Any ideas? And just to get back to the negatively switched components, true, but you would be amazed at how many European manufacturers have attempted to use positive switching in the past haha

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