73 911 2.4 MFI wiring issues

[jagErocks]

Just bought this car and it seems none of the MFI wiring cold start, temp sensors are wired . PLEASE NEED HELP.

[Winter911]

hard wire the cold start solenoid to a switch on the dash. The factory cold start is known to fail and cause issues in the MFI motors

[jagErocks]

So you mean just a hook up the wire to a switch and turn it on when I go to start the car cold

[jagErocks]

If you wanna text me, I can then send you some pictures of what I’m looking at
2505143366

[A930Rocket]

^^^ why not post pictures here so everybody can see?

[jagErocks]

Trying to but doesn’t seem to load my picture

[jagErocks]

[jagErocks]

Originally Posted by A930Rocket

^^^ why not post pictures here so everybody can see?

Just posted pictures I think…?

[jagErocks]

So my problem is, I have no wires going from the thermostat at the top back of the engine no wire going to the solenoid on the MFI injection pump and no wires going to the throttle micro switch and also the cold start solenoid on top of the fuel filter in the engine compartment on the drivers back firewall I found the wire just sitting under the carpet. It doesn’t go into anything. It’s not hooked up either and I don’t have a speed relay. Apparently I need a speed relay for something too.

[PeteKz]

If ou decide to have a new and correct harness made, I highly recommend Dennis Powell, "Timmy2" on this forum.

[jagErocks]

Thanks I’ll keep it in mind

[jagErocks]

Why is my relay box/holder on st rear engine so empty?
We’re the “speed relay” needed for the MFI to work?

[gerakroo]

The engine harness on the picture appears to be a later Carrera 3.2 version ?, (which does not have the microswitch wiring) The correct harness will most likely be this one:https://www.kroonwireharnesses.com/porsche-911/porsche-911-1973/wire-harness-for-engine-with-motorola-marchal-sev-generator-1972-1973-type-1
You will also need the speed relay for an MFI engine.

[rowingone]

You don't need the speed relay or any of that for cold start. As mentioned before just run a switched hot wire to the squirter solenoid on top of the fuel filter. hit the switch for a few seconds when the engine is cold and you bypass all the factory cold start complication. This is what I have on my 72 MFI. Are you sure there was no switch there somewhere . . how did the previous person start the car when it was cold?

[rowingone]

take a pic of the top of the fuel filter and also the drivers side of the throttle bodies to make sure you have the plumbing for the cold start fuel system. you should have a solenoid on top of the filter and small gas lines to each throttle body.

[rowingone]

the speed relay and micro switch are not for cold start but rather to prevent backfire when you let up on gas for downshifts. You get used to that . . and I kinda like it now. Don't focus on getting everything "back to factory" . . set up a switch like mentioned and you will be fine. I suspect that unattached wire runs to a switch between the seats or on the dash that has 12v for the start solenoid.