01 SW2 nostart, replaced CPS, died again

[SL2Many]

My SW2 shut off 3 weeks ago but restarted after sitting overnight. It nostarted last week; changed CPS; spark/fuel/compression all good. Today it shut off at 60 mph; cranks but won't start. No codes either time. Unless the new CPS is bad, what else?? Ignition module? Please advise--TIA.

[fdryer]

Mileage?

The next time it cranks and won't start, check for fuel at the fuel rail's test valve (fuel should squirt with pressure) and a spark test.

Cps' fail more often than ignition control modules. Icm's do fail. Junk yards icm/coil packs are cheaper than new. You can try cleaning corrosion off the icm, coils and bolts.

[SL2Many]

123,000 miles--after last no-start there was no spark but plugs were wet with fuel. After drying plugs, spark suddenly reappeared.

[Bernie]

If the plugs were wet then most likely you had no spark. Fuel was pouring into the cylinders but there was no spark to ignite it.

Check that all your grounds and the ignition module contacts are clean. Next time it happens first check for spark then for power at the ignition module.

[fdryer]

Wet plugs short out high voltage spark to ground long before it jumps the gap. Repeatedly starting a cold engine will quickly flood it.

[SL2Many]

It's getting fuel so i changed the ignition module (not coils). Starts/runs/drives but I have a mild bucking at part throttle. Should I change coils also??

[fdryer]

Arbitrarily replacing coils can be an expensive experiment. Try cleaning and swapping them to see if engine running improves.

Bucking can be from many issues; plugs, wires, icm, coils, injectors, fuel, etc.. It can be difficult to troubleshoot unless you have already checked, inspected, cleaned, and replaced what's necessary. Ignition coils rarely cause misfiring unless they're corroded and never cleaned; towers cleaned of corrosion and coated with some dielectric grease to prevent future corrosion - repainting rusted coatings with any spray paint laying around, replacing plug wires if they're older than 50k-70k miles. An often overlooked part is the egr valve that works quietly until it acts up by causing acceleration and cruise stumbling. cleaning it is half a solution while blocking off the two ports underneath it with a temporary blocking gasket can prove more fruitful - it either allows renewed engine performance or not. Coins, sheet metal or a soda can can be used for an immediate change in engine operation or not. If not then move on to other troubleshooting.

[Bernie]

Originally Posted by fdryer

Wet plugs short out high voltage spark to ground long before it jumps the gap. Repeatedly starting a cold engine will quickly flood it.

True, and if you need to crank several times, depress the accelerator pedal all the way down and hold it there to prevent engine flooding.