Double_take

I have a 1970 im getting back on the road and could use some help from the forum gurus.

The technical details of the install are below. Im able to ignition on, fuel pump runs, MSD box has lights, FAST computer comes on and able to begin setup. I set fuel pressure step, but when I turn ignition to CRANK I lose all power to computer (and presume pump and MSD box). power signal for all 3 are coming from Pink wire on Ignition (power is coming straight from battery). All the forum posts indicate this should be the perfect place. Why does computer shut off during cranking?


As title states, small block, fresh rebuild, I added a FAST EZ-EFI 2.0 system with return in tank aeromotive phantom pump, all lines are braided -6, FAST Dual sync distributor, MSD 6AL ignition with blaster SS coil. MSD box is mounted just below vacuum tank on DS. FAST controller is installed inside cabin behind map pocket (heater core is 100% removed).

Thanks in advance

cardo0

IIRC c3_dk had same problem with his FAST 2.0. Something 'bout the ECM sending the command to trip the motor if it doesn't see the correct inputs at startup. You may want to search threads or even PM c3_dk.

zwede

Would be interesting to do this:

Disconnect solenoid wire on starter (the thinner one that goes to the ign switch, not the battery cable). Turn key to crank (starter won't engage) and see if the ECU stays powered. If it stays powered up you have a voltage drop problem. If it turns off there's an issue with the ignition switch or wiring.

BlowAMouse

This is what i was also thinking. A volt meter on the battery would also help.

You say that you "lose all power to computer (and presume pump and MSD box)" Try to not "presume", there should be a light on the MSD box that you can watch, also have someone at the back of the car to listen for the pump.

If indeed you lose power to ALL 3, sounds like a voltage drop.
If only the computer shuts down, walk through all the connections.

When I install my FAST XFI, I triple checked all the wires and connections before starting it for the first time....yup missed one wire that did not allow the car to start the first time..

diehrd

You need power durring cranking and your losing it. The OEM distributor power wire is a safe bet for power crank/run ..

lionelhutz

The pink ignition wire from the ignition switch should have voltage in the run and start positions which means it's the right place to use when switching power for these components. It's possible you have a bad ignition switch and it cuts out when you move the switch between the run and start positions. I've seen that happen before. Typically doesn't matter much on a carb engine but can cause computer issues with EFI.

diehrd

The only way to know is to put a tester on the pink wire ..I mean it is a 1970 and over the years wires may have been moved or changed as each prior owner did his thing with the car.

Double_take

Thanks guys! I have some testing to do and will report back with more info.

Double_take

Im back, finally.

Problem was a voltage drop. The battery was a little lower than i thought. After a charge, everything fired up right away! I got through the setup procedure, had it up to operating temp, my electric fan kicked on and off (need to wire up the low speed setting), confirmed timing, even the 1975 tach calibration was correct.

Need to button up a bunch of small things, bleed the brakes, and get an alignment.

Metalhead140

Awesome, congrats!

Double_take

The engine sounds mean. It's been 4 years since I last heard it run. Now I'm on a mad rush to drive it before the cold moves in.

Double_take

What vacuum advance curves are people using? I've got 18-34 all in at 2800 for the mechanical. All the tech papers state use 16 degrees, but i know it shuts off or on at some point in the curve, what is this value? What would the curve look like?