Technical > Wiring & Sensors

VEMS on Supra MKIII 7MGTE?

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irishtwincam:
That tach signal is for driving a tachometer, its not fed into the ECU at all?
I think you understand this already, Ne should be used for CAS, tacho should just be for a gauge.
VEMS will drive a tacho gauge based on its interpretation of the Ne signal.
Bob will tell you how to set that up.

PeepPaadam:
Yes, I understand all this very well, after all, it's my 19th VEMS install ;)

Tachometer is not connected to ECU in original application. I won't use stock igniter at all, I bypassed it and driving coils directly from VEMS.

PeepPaadam:
Ok, got the correct rpm reading from engine using original triggers and 1.1.12 firmware. That resulted spark from all three coils ;D

But, I can't seem to get the fuel pump working? I connected the fuel pump relay wire (GND) to VEMS and activated it but nothing. P259 outputs are just fine because I connected EFI MAIN RELAY also through that and it functions just fine. Tried to connect fuel pump straight to GND but heard no buzzing.

What do i have to do to get the fuel pump working? Is it related to 2speed relay and additional fuel pump wire from the OEM ECU?

rob@vems.co.uk:
What happens if you ground the EFI pump relay pin?

irishtwincam:
On 7mgtes theres a dual speed fuel pump relay I believe.
There might be some fanciness to get it working.

7MGTE MA70 owners have issues with a dual voltage relay feeding the pump.
Low voltage for lowrpm/cruising, higher voltage at high rpms/load.
During transitions the pump voltage drops and risks leaning the fuel mixture.

Its a recommended mod to bypass stock wiring and feed the pump the 12v from
the max fuelpump rated fuse.

Best to run this suggestion past some hardcore MA70 dudes first.
There may be another wire on the MA70 ECU that when earthed triggered the fuel pump relay to turn on.
Toyota had something similar on early AE86s.
The Fc wire switched on the power TO the injectors.
Perhaps the MA70 stock is killing power TO the pump because an undocumented wire needs earthing to switch a magic relay?
The Fc wire is not on later AE86 looms, maybe the same is true for MA70 looms?
There could be variations?

HTH

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