MSefi.com read only forum (Jan.15,2018)

I am a total newbie here, I run a custom automotive wiring shop on the side, to support my sandrail habit. I am a master electrician with 30 years experience, have a fair bit of plc programming experience under my belt as well. One of the cars i wired many years back, was a Hot Vws magazine feature car.

A customer dropped off a aircooled vw with a turbo, and most of the parts of a claudes buggy efi kit .
He had wired it himself, and lets just say it was a disaster waiting ....enough said guy is a good friend .

He had it started and running, but only at idle,( ran really smooth ) as soon any throttle was added, it went nuts I suspect some wiring errors.
I am fabricating a proper harness, spiral wrapped ,oil and gasoline proof wire, (not speaker wire like the last attempt )weather pack connectors, strain relief connectors, when passing thru firewall ...well you get the idea

Sorry for the long intro but you needed some background
I don't have much to work with as far as a wiring diagram and what i have is just a bit vague
The drawing is titled Megasquirt power distribution board Bowling & Grippo
Document Number V1.2 Rev 1.2 wednesday ,May1,2002 .Is this unit considered a Megasquirt 1

I have everything pretty figured out but there are a few items i find lacking in clarity

1)There is a part of the drawing labeled JP2 terminal block +12volt supply for the injectors .I take it this requires a separate 12 v feed switched or unswitched ? and I am only going to power up pin 1 and pin 3 is this correct ?

2)I am pairing up cylinders 1&3 4&2, for cyl 1&3 i am taking a feed from pin 1 of JP1 term blk, to operate those two injectors at the same time, and a feed from pin 3 to fire cyl 4&2 that part is easy ....but where do i return those injectors to

Last question define engine ground i am going to run a dedicated grd wire to my engine block but does this wire not also need to be tied to battery negative i find this just a little confusing

Thanks in advance 2088bob

Thank you moderator for moving this to the appropriate forum. I as one of the moderators of the Shoptalkforums.com Electrical forum appreciate that

The connections i am asking about are on the relay board

I take it this one does have a relay board?

The JP2 header powers the injectors and should have power on all four pins. Check the fuses. The injector return wires go to the first four pins on the long terminal block.

Yes Matt he did buy the relay board

I appreciate you taking the time to answer my question

so if I understand you correctly i go from the JP2 terminal block of the relay board out to power up the injectors call it injector +12v and then take -12v or ground or return wire of the injectors to pins 1,2,3,4 of terminal strip JP1 of the relay board

Do i have that right

My intent is to only take one trigger or +12v signal to each bank of cylinders (this is a flat four acvw I am working on ) and one return wire and fire the injectors as pairs on each side

Yep! Here's a pinout of the relay board.

Ring terminals:
Engine GND: Ground to engine block.
Switched 12V: Connect to a source that has 12 volts with the ignition key in both Run and Start positions.
12V Batt: Connect to an unswitched 12 volt source like the positive battery terminal.

Injector +12V block: Supplies 12 volts to the injectors

Main strip:
INJ2: Return connections for #2 injector bank
INJ1: Return connections for #1 injector bank
FP: Supplies 12 volts to fuel pump.
FIDLE: Supplies ground or 12 volts to on/off fast idle valve. Default is ground, but this can be changed with the J1 jumper.
S1: Connects to pin 25 on Megasquirt. Used for stepper IAC (MS-II) or user configurable outputs with appropriate modifications.
S2: Connects to pin 27 on Megasquirt, used like S1.
S3: Connects to pin 29 on Megasquirt, used like S1.
S4: Connects to pin 31 on Megasquirt, used like S1.
S5: Connects to pin 36 on Megasquirt, used for ignition control on a V3.0 board.
VREF: 5 volt power supply for TPS.
TPS: Signal from throttle position sensor.
TPS Ret: Ground for TPS.
Tach: Used to send Megasquirt a tach signal. Connects either to an RPM output, crank trigger, or negative terminal of the coil; the precise use depends on your ignition system.
MAT: Connects to one terminal of the manifold air temperature / IAT sensor.
MAT Ret: Connects to the other terminal of the manifold air temperature sensor.
CLT: Connects to one terminal of the coolant temperature sensor.
CLT Ret: Connects to the other terminal of the coolant temperature sensor.
O2: Connects to oxygen sensor output or wideband analog output.

The MAT and CLT sensors have no polarity, so you can connect them to the relay board either way.

Again Matt many thanks I am going to use fp to trigger a fuel pump relay

And the engine ground i will connect to the engine block which then finds it's way back to battery negative thru engine to trans which is grounded to battery

this is how we are coming along






Is there some kind of cover available for the rely board?