If someone already covered this with pictures... just kill this thread. Or if I've missed an easier way to do this... kill it... or repost that info for people.

So.. I know we've talked about the fuel pump wiring being accessible under the dash... it is... and very easily. No need to run outside to the diagnostics stuff... or jumper that fulltime for your fuel pump.

Just run one wire from the MS harness over to the driver side kick panel... its all there... here are the pictures that "guide" you to the wire.

The wire is light green.
So... start by heading for the hood latch area.

Now lower your head to the floor... and start peering directly behind the hood release area.

Back there there is one plug you want....

Close up of it


Simply tap that wire for the fuel pump control out of the MS. Works fine... you'll get prime on initial "ON" position and then fuel pump while on. At least... I know mine primes and shuts off before cranking.

 

damn i thought that one was it...

 

Seems like that would work fine, but there has to be another way. My PNP didn't require running a wire for the fuel pump, so there must be a way to trigger it from the ECU harness.

Ben

 

Yah, I figured that... but took the lazier route... lemme look at my schematics here and see if there is a wire on the ecu side that we've just missed out on.

edit: after a quick look... nothing is obvious that goes from ecu to the relay for the fuel pump. I've got a few wires heading there... but looking at the schematics... sorta looks like they control something else. A violet line from the 1 plug might regulate something... but unsure.

 

I bet something on the extra board on the mspnp pulls the fuel line to ground. If they gave away the secret though, that would be one less selling point over building it yourself. Tapping the wire with a vampire clip isnt really a big chore though.

 

No, they are open about it. I know the FP is controlled by a transisitor inside the PNP, just don't know what wire on the ECU harness is used.

 

Whats the VIO wire on pin C of connector #1?

http://www.madracki.com/miata/images/wiring/90diag.pdf

 

1C on the schematics I have from brain... show it to be an Ignition switch.

It's the 'vio' violet wire I mentioned that goes to the same relay... but I'm unsure what it controls or how.

 

go to p4 on that pdf, the violet wire go through some switching circuit to the fuel pump.

other wires going to the switching circuit are ignition live, one to the diag port and ground so i'm 99% sure that's the right wire for the 1990 mk1.

 

Question is... how does the violet wire trigger it. Power or ground?

 

just vampire the ground and call it day

 

Thanks alot for this write up splittime. It is exactly what I ahve been looking for. I suggest you add it to the sticky about how to MS your car. That way for future refrence of newbies wont have to search the whole forum for hwo to do it.

 

I've got an inertia kill switch from a Ford Taurus that i want to wire with the fuel pump. I am planning to install it either inside the trunk or screw it down on the driver side seatbelt harness tower for easier access. Has anybody done this?
My only hesitation is if its too sensitive that it might trip on me while driving on a roadcourse track.

 

That is a great idea that I've been preaching for a while. Thought my pleas were totally ignored. Mine came from a Mustang. Mine is under the dash. No, you're not going to trip it while driving.

 

if I had to guess, VIOlet wire is the normal fuel pump operation wire. it goes to the ignition switch. looks like just another input to the fuel pump relay "circuit opening relay".

Since the other wire on that coil goes to gnd, I'd say violet triggers the pump when it's hot +12. same wire goes to BLK-BLU "IG2 ST" (on while cranking AND running)

The LT GRN wire grounds to turn on the pump it looks like? Via the airflow meter or diag connector.

 

airflow meter, gets grounded.

 

so wait the airflow meter simply turns on the pump as soon as it does anything?

 

yes. there is a switch controlled by the afm's flapper door.

 

Ben:
how did you wire the inertia switch? I am using a relay board on my MS install. Do I just wire the inertia switch in series on the negative side of the pump? Would it be able to handle the current load of the fuel pump?

 

You'll notice that is a dual coil relay there.

One way to activate the relay - which we used on our MR2, a car with a similar circuit, but didn't use on the MSPNP - is to send a ground signal through the AFM wiring by putting a jumper in the AFM connector.