I'm putting in a new FAST XFI on my '95 LT1, and it won't start. I am getting fuel and when I crank the engine it will fire once or twice, but won't turn over. I talked to FAST and they said that everything is connected correctly and should be working well and they don't know why it won't start. I'm new to tuning so I assume the no start is due to my lack of experience with that. Any advice on where to go from here to get it started.

I do have an after market camshaft (Lift: .576/.571 Duration: 280/288) which I assume would be the reason why the base tunes for the FAST XFI won't get me to start.

 

Can you explain what you mean by "it will fire once or twice, but won't turn over." Do you mean the starter isn't turning the engine over?

 

My apologies I said the wrong thing, I did not mean it won’t turn over, I just meant it won’t start. What happens exactly is when I turn the key the engine cranks and then after about 5-10 seconds one or two cylinders will fire, but won’t keep firing or start

 

So are you saying that you only have spark on one or two cylinders?

The first thing you need to do is verify you have spark to all cylinders and verify that all 8 injectors are spraying. I think the easiest way to do that is to spend $5 on this at Harbor Freight

Just pull the fuel pump relay or pull the fuel pump fuse. Then try each cylinder and make sure you have good spark on all 8. Assuming you have good spark then pull the fuel rail off. Leave all 8 injectors on the rail with the fuel line and harness hooked up. Hold the rail up and away from the engine the best you can and crank the engine (after you put the fuel pump relay or fuse back in). Verify all 8 injectors are spraying.

After that I like to check the function of the IAC. Personally I like to first make sure its moving correctly. So I remove the throttle body from the intake. Plug the IAC into the harness and turn the key to the on position. Don't make the IAC move without being installed in a throttle body. The pintle will fly across your garage. Kinda neat to see but can be an expensive mistake. You should see the IAC pintle move to it's home position and then to it's park position. Turn the key off and on a few times and watch and verify that it's moving.

If all that is good then you need to look at the tune. If it's an IAC problem then you can usually hold the throttle body open slightly and get it to fire. Too much fuel during cranking is easy to spot. The engine will flood quickly and you'll smell fuel. Too low crank timing (much under 10 degrees) can also cause starting issues. So check that.

 

Great thank you, I won't be able to work on it until Friday so I'll check for spark and fuel then and update how that goes. In the FAST XFI operation manual it says to set the crank reference angle to 1 degree for optispark ignition, so although that is under 10 degrees I don't think that the crank timing would be causing it not to start.

 

Check the basics, make sure the firing order is correct, make sure all eight injectors are firing (Noid light), make sure all eight plugs are firing. Check your cranking timing and make sure the actual timing matches the commanded timing. On a LT1 you will have to rig up some TDC indicator so you can verify this.

Also check to make sure you have compression, if you changed the cam you may have the valves set too tight.

If you have spark at the correct time and fuel it will run.

 

Update: The car is running now. It was a simple mistake on my end, on the attached wiring diagram of the ignition harness for the FAST XFI, where it has you add a wire for factory coil driver I did not disconnect the wire from the stock PCM and just spliced the two wires together. Must have been getting interfering spark signal causing me not to get spark. I hadn't been able to work on it today and I disconnected the ignition signal wire from the stock PCM and connected the wire I added directly to the connector and it started right up.