Rebiult, now no spark!

[Tofuball]

I've got a 95 Firebird with a 3.4L.

I rebuilt the heads and now I've got no spark for some reason.

The tach also does not bounce when trying to start. (I think it gets its signal from the coils)

However, the ECU is seeing a tach signal of around 200-300RPM, and it is injecting fuel properly. (I read that with a Snap-On MT2500.) Fuel pressure is perfect.

The ECU is not telling the coils to fire for some reason.

I'm pretty sure I plugged everything back in where it came from, and it worked when I drove it in to the garage to do the head work.

Any suggestions would be very much appreciated!
- Jason

[1988GTU]

Make sure your ckp sensor is plugged in or not broken.

[Tofuball]

Define CKP sensor, and how would I check it?

[1988GTU]

Crankshaft Position sensor aka CKP:

[Tofuball]

OK, I'll give it a look again when I get home.

Thank you!

[Tofuball]

OK! I think I found the problem!

The sensor thats on top of the block, under the intake manifold, it is not getting the +5v signal it is supposed to. Any idea why that would be happening?

[IsaacHayes]

Check the wire for breaks in it. The next step is verify the pin from the ECU there is giving 5v output. If not then ECU might be bad..

[Joseph Upson]

OK! I think I found the problem!

The sensor thats on top of the block, under the intake manifold, it is not getting the +5v signal it is supposed to. Any idea why that would be happening?

What sensor under the intake manifold are you refering to? For your 3.4 under the manifold would be in the lifter valley. Are you sure the pump is running while cranking and not just the 2 second power up on ignition on? If you are not getting a spark the pump should not cycle when you are cranking the engine.

Check your ground wires and make sure you didn't pinch a wire on reassembly.

[Tofuball]

Check the wire for breaks in it. The next step is verify the pin from the ECU there is giving 5v output. If not then ECU might be bad..

Well, the ECU isn't outputting 5v, I have an ECU from a 95 3.1 Lumina, can I swap that in just to see if the ECU is the problem, or are they too different? Failing that, anyone got an ECU I can borrow, and maybe buy? :P

What sensor under the intake manifold are you refering to? For your 3.4 under the manifold would be in the lifter valley. Are you sure the pump is running while cranking and not just the 2 second power up on ignition on? If you are not getting a spark the pump should not cycle when you are cranking the engine.

Check your ground wires and make sure you didn't pinch a wire on reassembly.

Well, more "in front of, and under, the IM"

I'll recheck the grounds again.

Thanks all for the advisory.

[ForcedFirebird]

Well, the ECU isn't outputting 5v, I have an ECU from a 95 3.1 Lumina, can I swap that in just to see if the ECU is the problem, or are they too different? Failing that, anyone got an ECU I can borrow, and maybe buy? :P




Well, more "in front of, and under, the IM"

I'll recheck the grounds again.

Thanks all for the advisory.

You mean the cam timing lobe? If it malfunctions, the motor should still run, you will lose SFI and be batch firing.

[Superdave]

Crankshaft Position sensor aka CKP:

Crankshaft Position Sensor... is the CPS..


CKP abbreviates what???


to the OP, check all your grounds and make sure the ICM (Ignition Control Module) has all 3 plugs in it, and the plug wires are on correctly.

[bszopi]

CKP can mean crankshaft position sensor : http://www.v8sho.com/SHO/CrankshaftP...sorRemoval.htm

[Tofuball]

You mean the cam timing lobe? If it malfunctions, the motor should still run, you will lose SFI and be batch firing.

Hrm, well the ECU isnt sending that 5v for some reason.

Crankshaft Position Sensor... is the CPS..


CKP abbreviates what???


to the OP, check all your grounds and make sure the ICM (Ignition Control Module) has all 3 plugs in it, and the plug wires are on correctly.

It's got all 3 plugs in it, and the plug wires are all in correctly, the ICM is not getting the signal to fire, that is the issue.

[ForcedFirebird]

Hrm, well the ECU isnt sending that 5v for some reason.

I just mean that the wire comming out of the front of the engine near the t-stat housing, it won't cause the engine not to run.

It's got all 3 plugs in it, and the plug wires are all in correctly, the ICM is not getting the signal to fire, that is the issue.

Connections are good? If the ECM is not getting signal from the ICM...
Have to start with hardware.

I would be at a loss in this situation.

Have you tested the CPS?

[Superdave]

CKP can mean crankshaft position sensor : http://www.v8sho.com/SHO/CrankshaftP...sorRemoval.htm

Ford info dosen't count, they're all backwards anyways...