3100 Lumina No Spark

[camaroz28lt4]

Ok well heres the deal, We bought a 97 lumina 3100 off of my friends aunt and it had an engine noise. It only has around 90k on it. The car started fine and everything but was knocking. So we pulled the engine and my dad rebuilt it. We put the engine in last night and went to start it and it just cranks. It is getting fuel, but no spark at all. It ran fine before we took it apart, so im confused on what could be causing this. I wouldnt think the ignition module would crap out in a week or so with just sitting there, or all of the coil packs crapping out all at once would be very odd. Not sure if anyone has had or heard of this problem before, but any help amazing. Since my z28's do not move in the snow, I would love to get this car driving. Thank you for your time. -- Paul

[3100 MPFI]

check the crank position sensors, and cam sensor. Crank position sensor on the back of the engine in the middle of the block. Kinda hard to get too. If it is not new, it could have easily been damaged when the engine was being rebuilt. Also, check the wires to make sure they didn't get crushed. I acidentally crushed mine between the block, and the ac bracket (you dont have an AC bracket, but still check for damage.

There is a second crank position sensor under the harmonic balancer. Make sure it, and it's ring are not messed up, and it is plugged in, and the wires are not broken.

The CAMSHAFT position sensor is located under the power steering pump going into the block next to the lower intake manifold (going straight down). The wires get brittle and break if you are not careful.

Also, the plate for the DIS needs to be grounded really good, to the engine. Did you clean the plate, or did grease get on it?

[camaroz28lt4]

One thing I did notice a little bit ago, when cranking the tach does not move at all, not sure if that would give any indication what could be wrong just an observation. The plate for the DIS? What does that stand for, probably going to kick myself when you say that but oh well. thanks again for the help

[SappySE107]

distributorless ignition system. Its the 3 coil packs on top of the motor. The ignition module is bolted to a plate that is bolted to the upper intake and the studs off the rear head.

[camaroz28lt4]

ok well that makes enough sense haha. well would the tach not showing a rpm change mean a crank pos. sensor not working correctly? Thanks Paul

[SappySE107]

Yeah, sounds about right to me.

[camaroz28lt4]

Alright one more dumb question. When hooking the wires back up, we had to disconnect the VSS plug of the transaxle or whatever its called. Can that plug and the crank position sensor on the back of the black possibly be interchanged, I will check tomorrow, just wondering if that is even possible. Thanks again. These 3.1s are more complicated than and more of a headache my 500hp LT1 car is!

[SappySE107]

no, they cannot be swapped. The computer will need the vss but that isn't going to stop it from getting spark.