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View Full Version : F.A.S.T. XFI setup: Timing/Spark issues on a gen1 427 sbc in a c3 vette



CorvetteDave01
09-23-2007, 05:37 PM
Hello all, hoping some of you guys have some FAST xfi experience, not many in the C3 forum do it seems. I have a '76 vette with a 427 sbc genI motor, AFR heads, 5-speed, naturally aspirated, solid roller cam motor.
-Have the edelbrock proflo efi ported intake, 1000 cfm throttle body and fuel rails, 48 lb venom injectors, A1000 Aeromotive pump, -8/-6 send/return braided lines, MSD 6A box and blaster 2 coil; FAST dual sync distributor.

I recently traced my wiring (main for '76 vette) short and got the FAST efi system hooked up to my 427. Downloaded the 427 na basemap and set the injector rating to my 48 lbs (as per FAST techline instructions). Calibrated the TPS sensor and will do the MAP sensor and temp sensors (if needed) tomorrow. So I should have a good start up basemap according to FAST tech.

1. Wired the MSD 6A box to the FAST ecu with the 'white' points wire.

2. Followed the directions as follows and timed it too, but only getting 1 spark instead of multiple when cranking the engine over.
-set balancer at 50 BTDC
-Point the distributor at #1
-Rotate the distributor counter clockwise till the cam, then crank LED lights up.

Again, I am only getting 1 spark when I crank the motor, shouldn't it continue to spark a plug when cranking like a normal distributor? Thinking the timing is wrong.

Any suggestions?

Blown353
09-23-2007, 07:48 PM
Sounds to me like you have the cam sync signal of the distributor hooked to the crank input of the XFI. This would mean the crank (spark) input of the XFI would only be triggered once per revolution of the distributor as the cam sync signal only pulses once per rev.

The dual sync distributor's crank output gives a signal 8 times per revolution (firing each cylinder) but the cam signal outputs only once per revolution (to tell the XFI that the next crank signal is the first cylinder in the firing order so it can perform sequential injection.)

If you have them hooked up backwards then injection firing order sync will be off and the XFI will trigger your MSD box only once per distributor rev.

You can verify if you have it hooked up right by looking at the status lights on the XFI box. Check to make sure the cam status light on the XFI is on when the cam status light in the distributor is on. If the cam light in the distributor is on and the crank light on the XFI is on then you've got the wires switched.

Fuelie Nova
09-23-2007, 08:09 PM
Dave
I just got your email but I will answer here. Make sure you check your MSD box. There are instructions on MSDs site on how to check. My setup did exactly the same thing and the box was bad. I would ground out the test lead and the box would spark the first time then nothing after that. It is a simple check. Do that first then we could verify the pin out on the fast dual sync connector.
Tg

CorvetteDave01
09-24-2007, 06:20 PM
Thanks guys, but I did get it figured out. The 'leading edge' for the crank sensor should be as soon as the LED light comes on after the cam sensor imo as well since the rotor would be spinning the opposite direction.
Anyway, I figured out the problem and of course it was something stupid. I had everything setup perfectly except for the ignition wires to the computer and distributor, so that when I was cranking, no power to the distributor or computer to tell the ignition box when and if it needed to fire the coil.
I did get it started and ran it for about 30 seconds, runs rough still, but it runs, so I am pumped! I did verify some of the global settings under the default basemap I flashed to the ecu (427 na with 60 lb injectors): Verified the IPU on ignition; 50* on the timing sync setting; timing order, injector size; calibrated the TPS. Still need to calibrate the MAP and temp sensors and I should be ready to start tooning.
Now I just need to finish setting up the sensor calibrations, reassemble the dash (not fun) and start tuning with the wide band.
Thanks again for all of your help, should have it on the road this weekend finally.