2001 SL1 200K miles. Stopped running, but cranks. Tested for spark between coils 1 & 4, no spark, so I replaced the crankshaft position sensor CPS. (The last one was replaced about 3 years ago, cheap thing.) Bought an ACDelco replacement. The old one measured 80 ohms cold. 250 is minimum R so I thought I'd found the cause, but no. I had to jury rig two wire ties to keep the connector on since its clips snapped off. (Since the signals are so tiny and I'm so talented with wire ties and solid signals from the CPS is so critical, I ordered its replacement connector. That comes in tomorrow.)

Following the CPS replacement I cranked and tested coils 1 & 4 just like before, but no spark. Way back when it stopped, January, I had finished a drive somewhere around town, nothing unusual, no codes being thrown. I parked in front of the house, and later that day or the next day it wouldn't run—cranking only. No other funny business. I considered myself lucky it conveniently crapped out at home! 707

Replace the connector tomorrow. General snooping on the web suggests swapping coils and still looking for spark. If there's spark on the 2nd coil, the first one's bad, but wouldn't there be *some* ignition from the two good cylinders? Then if neither are good I'm told it's pointing to the ignition control module, ICM. It confuses me that coils can stop working. In my brain they're solid state devices.

I searched the forum for "cranks but doesn't start" and only found one that was fuel related. I didn't find any that talked about no spark. I thought that was odd. So I'm learning more about SL1 spark and with really crappy tools and not wanting to do the work <cue baby crying, "Waaah!" in my own voice> and I need to ask for help.

Help. ;-)

 

Do you have spark on the other coil? If so, Switch them and see what you get. If you still don't get spark you know it's NOT the coil. Then we check wiring.
What do you have?

 

…I know it's not the original 1&4 pack that's going to be bad since I just moved a working coil into position 1&4 that should also work, so its failure is coming from further upstream.

In college I was told I thought too much.

I read what you wrote, but I can interpret it in two different ways, so I'm immediately confused. You're saying…

Reattach the connectors on the 1&4 coil, pop the connector on the 2&3 coil, and check for spark between the coil terminals for two and three. I get that.

When you write "switch them," do you mean

A. physically move them, the actual coils,
B. or switch the connectors between the two coil packs, leaving the coils in their current positions?

Something about this situation is giving me the most unsettling and uncomfortable feeling. I didn't know why. I think it's coming from too many options in my brain all at once. Learning can be fun but it's not fun. 707

I don't know what's on the engine side of the coils, but it has to be a current supply line and lines from the ignition control management system ICM and the power control management system PCM.

If I physically switch the coils, and if there are plugs on the other side of the coil that they plug into, then switching a coil right to left substitutes one for the other. Running a test and looking for spark, I can tell if a coil is bad based on spark appearing.

A pair of non-sparking coils could be bad coils, but could still be bad wiring. Thus, your your comment about "checking wiring."

If I get spark on terminals 2&3, but switch its pack to 1&4 position, 1&4 position sparking would point to the other pack being bad; while 1&4 position not sparking with the coil from position 2&3 would be inconclusive.

Whew!

 

Remove each coil and have them switch places. That's only if the other coil is working. You have spark on 2 and 3 but not 1 and 4, correct? If that is correct then do the switch. If you don't understand this I suggest you take your car to a shop.

 

Dang it I wrote a pretty response but it appears an electronic dog ate my homework.

CKP not CPS should be 700 to 900 ohms.

Confirm the 2 3 coil still has an arc between the towers while cranking immediately before doing the following:

Physically swap the positions of the coils on top of the ICM.

Make sure there is no corrosion on the bolt surface that contacts the coils as the coils are grounded through the bolts to the bell housing.

plug wires stay off. All of them

If the coil now in the 2-3 position still does not arc but the coil now in the 1-4 position does arc, then the coil NOW in the 2 - 3 position is likely defective.

If the coil NOW in the 2-3 position does Arc and the coil NOW in the 1-4 position does not arc Arc, there is likely an issue with grounding, wiring, or the ICM itself. Carefully inspect the pigtail that goes to the ICM.

If the coil now in the 2-3 position does not arc and the coil now in the 1-4 position does not arc, the test is inconclusive with respect to the coil packs but again probably indicates grounding or ICM or wiring issues.

Those are the three possible outcomes. Put the coils back in their original positions so you don't lose track of the one that originally had no arcing.

There is a service manual based diagnostic tree to follow to confirm it is the ICM if things point in that direction.

 

As for no ignition of fuel on 2-3 with spark, you need air spark fuel and compression.

Remove the air ducting and check for a rodents nest. 6 months through the winter....

Assuming fuel in the tank is 6 months old... Don't know if that's long enough to go bad....

Let's get it sparking on all four cylinders first

 

After a long delay, I've replaced the crankshaft position sensor, and also its connector. I've confirmed there's no spark across the 2-3 posts nor the 1-4 posts. I've taken the ICU and the coils off the engine block. The connection to the block looked a bit dirty but no corrosion. Secondary coils read 840 ohms each. I can't get a reading off the primary coils. It may be a low ohm meter battery. I read somewhere where they should be 1-1.5 ohms.

As Derf said both coils failing points to grounding, ICM, or wiring. I saw some light rust on the hold down bolts so my next step is to clean all the metal faces and reinstall. That'll eliminate the grounding. If it still doesn't work it'll point to ICM or wiring.

Don't wish me good luck—wish me good skill. Thanks.

 

Have you pulled the ICM fuse and measured it for continuity?

 

I thought I remembered pulling it and looking at it, but as I went back on the web to look for an image of the fuse block, there's nothing that's labeled ICM. I read somewhere that CPK, ECM, and ICM being all interrelate are sometimes sharing fuses. Not much solid ground to stand on, it seems. :-P

 

My apologies.
It's a 10A fuse labeled EIS in the underhood junction box.

EIS = Electronic Ignition System, (which is more than just the ICM)