Yet another "Help! My car won't start!" thread
 

Ok, so I have an LS-1/T56 from a 2002 Trans Am sitting in my 1972 Datsun 240Z, and it aint starting. There is no spark, and I don't think the fuel injectors are going either. I'll start with fuel:

We have a fuel cell, with pump and filter, which goes to the rail, and a custom return from the rail. The regulator is after the rail. We have 60psi. The fuel level sensor is not wired (if it matters). With the ignition on "ON" we get a constant 5.7 volts at the injectors. during cranking, it drops to 4ish, with no cycling on and off. Thats pretty much the fuel system.

As for spark:

We have a PCM, flashed for 2 O2 sensors, VATS delete, original tranny was auto, but PCM was also flashed for T56, and a little bit of performance tuning. The engine wiring harness is not from this engine, as we now have a T56, not the auto tranny. There is a small problem this is causing, but I will get to that later. We do not have any of the dash/body wiring harness or the gauges in right now. We do plan on stripping the dash/body wiring harness to let us use the original gauges, and get rid of everything else not needed.

We have tested so much, time and time again. The orange wires are 12v all the time, the pink get 12v from ignition. We have tested that the power is getting to the pins, and all the grounds are good. The crank and cam sensors are plugged in. Pink wires at all of the coil packs are getting 12v. We have a clutch pedal switch that grounds the starting relay when it is pressed in, and just today (temporarily) grounded the wire from the PCM for the clutch pedal. This way it is always thinking the clutch is in for starting.

There was a code it threw: P0452: Fuel Tank Pressure Sensor Circuit Low Voltage, but we fixed that my putting some voltage through some resistors to the wire (3v worked good)

As for the problem with the harness:

It all fits good, except for the oil level sensor. I'm not sure what car the wiring harness came from. The sensor in the oil pan has a 2-pin plug port. the plug on the harness has 3 pins. I read on here that all the sensors on this block are grounded through the block, so I tested the wires, and found that one of them goes to ground. Neither of the pins on the sensor went to ground. I hooked up the 2 remaining ports on the plug to the sensor. I wasn't sure which wire went where, so I tried both ways, and neither worked. I read on here that the C5's won't start with this unplugged. However, we are not getting the code...

I'm gonna try swapping the PCM into another f-body tomorrow to see if it's the problem. Other than that, I'm lost as to what it could be, unless its like a bad crank or cam position sensor...

What do you think?

Are you sure the 3 pin plug you are trying to plug into the oil pan isn't the crank sensor? What are the wire colors?
Also, when you check voltages, you need to check them DURING cranking, not just with the key on. It's very common for people to hook up to an ignition switch terminal that is hot with key on but dead during crank.

The oil level sensor in the pan has nothing to do with the engine running so forget about that. The 3 pin connector you are calling the oil pan plug sounds VERY fishy.

Need more info.

I agree that you may not be checking power when cranking

OK. Yeah. I feel like an idiot, but an idiot that will be driving very fast, very soon!!!!

So I had the two switched. I dunno how the 2 prong plug fit into the crank position sensor... huh. Well, now that thats taken care of, its time to go get me a Taurus fan and finish the cooling system. Oh, and she sounds like a beast with the open Sanderson headers :D

Oh, and I'm not gonna be using a heater. Whats the best way to plug the heater hoses? Should I bridge one to the other, or plug them individually? And if plug them individually, whats the best way to do that?

You have anymore info on this?

Simple to check. Just put a voltmeter or test light on one of the pink power feed wires to the coils or injectors. You'll see 12 volts with the key on. Make sure you still see 12 volts (or test light remains lit) when you start cranking the engine.

Makes perfect sense, thanks.