No spark after R&R'ing 4.3L heads in 2001 Blazer
 

Used to wrench and smog 25 yrs ago, thought I could help my 20 yr old R&R bad heads on his 2001 4whl-dr Blazer. Probably a big mistake, but old motor heads don't die easy. Issue: it's all back together, but distributor was removed and engine turned over so I cold-timed it and re-set to #1 plug at tdc. No spark...recharged battery and heard different stuff clicking at below-dash, front passenger seat...disconnected battery for an hour then re-connected. W/ ignition key on, fuel pump runs for 2 sec's (good!), and engine turns over---but no spark when pulling coil wire. All 50,000 sensor and gizmo wires are back in place, God willing...so I'm stumped. Did check fuses--can't find any bad ones. What, short of dragging it to a shop somewhere, should I do? Thanks in advance for any help....

If you set the distributor to cylinder 1 at TDC with the rotor pointing to the #1 cylinder, you did not set it in correctly. Follow the EDI Engine Timing thread to a 'T' and you should be good. If not, then you know that is not the issue and need to look elsewhere.

swart, thanks...will follow the instructions next, but unless I'm missing something, it shoudn't matter if the firing order's out of whack--it should still produce spark at the coil tower. And it doesn't. I've confirmed that the distrib is in with rotor contacting #1 tower with crankshaft showing TDC on #1 cylinder. But--even if that's wrong, it should still produce spark at coil, no? Thanks again....will go next to your previous post's instructions and follow them to that "T".

Reason says that it still should produce a spark from the coil wire. But with the PCM using inputs from the CKP and CMP sensors to time the spark, if things are too far off for the PCM to do so, it may not spark at all.

I would try rotating the engine over until the crank pulley is aligned like the thread I linked to states and then look at the rotor position to see where it ends up. If it is not at the pointer with the '6' on it in the base of the distributor body, then you will need to remove it and step it one tooth at a time until it is properly aligned.

2001 Blazer, no spark post-head R&R
 

We set distributor timing per EDI Engine Timing instructions, and still no spark. Quick-checked for voltages at all interconnects for sensors/gizmos we disconnected/connected to replace heads.... (distributor, cam sensor, MAF, etc) and seems like all have a lead with either 12 or around 6 volts. No blown fuses, and car ran before we started. What would prevent spark at coil? (Yup...coil wire is good). Could it be the computer? Help......thanks......

Run through this diagnostic procedure:
98+ No-Start - Engine Cranks OK - Ignition System Diagnosis

Missing Spark Mystery Solved
 

Swart, thanks for your help---great service to us Chevrolet owners out here.

The missing spark mystery was solved after lots of hair-pulling and gnashing of teeth, and a little close inspection of electrical connectors. Turns out secondary voltage was missing at ignition module, which led to the crankshaft sensor. Car had been jacked up and that had somehow tweaked the wires into the connector at the crank sensor. New harness/connector and that problem was solved. Next issue was distributor was in wrong, despite our efforts to carefully follow EDI directions. We mistakenly set rotor to #1 cylinder's contact point inside cap, instead of pointing it at #1 marking on outside top of cap. There's a difference! Re-set that, and it fired right up. Egads....what an old dog won't do to learn a new trick! Thanks again for your help!

Glad you got it running and thanks for the followup. Maybe someone in the future that's pulling their hair out about the same type of problem will find answers here.

EDI timing instruction ?
 

help me understand what your saying because i see that the 6 on the left center of the dist base is at the 9 oclock and there is no post inside the cap , the #$1 is at 8 oclock , it fed into place there a couple of times but i kept taking in out until it ended up on that 6 mark and no go , as the 8oclock post inside the cap goes across inside the cap to #1 plug at 3 oclock inside the cap , is this not where it should really be ? :icon_shrug:

on a 2001 chevy blazer how do you test an ignition control module