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**19902drlumina** · 03-21-2006, 12:08 AM

knock sensor?

**bszopi** · 03-21-2006, 12:11 AM

Definately check all the engine grounds. I've had something like this happen before after I re-installed my engine once. I hadn't tightened the ground at the tranny enough and I had some very odd things going on, including wierd guage flucuations and no cranking. And it was an intermittent thing for about a day until I found the issue.

**pmpnb** · 03-21-2006, 01:10 AM

hey

the lights coming on afterwards is a security feature

**Mr Project** · 03-21-2006, 10:39 AM

Re: hey

Originally posted by pmpnb

the lights coming on afterwards is a security feature

Yeah, but the dash lights? This just seems bizarre to me, maybe I haven't owned enough early 90's GM cars.

Engine grounds are a good point. Visually they looked ok when I had everything apart, but I'll add a really good engine ground straight to the battery temporarily and see if that helps.

**Mr Project** · 03-22-2006, 08:16 AM

Well, I added a nice fat ground from the engine to the battery, and no change. Cranks great, no spark. I think tonight I'll try removing the ICM again and having it tested at the parts store....I'm running out of ideas!

**19902drlumina** · 03-22-2006, 02:45 PM

id test ure icm and cranksensor. it wouldnt have been aground cable for the bat because u were turning over. in the manual it says (trouble shooting Engine rotates but will not start; 1 fuel tank empty, 2 doesnt apply u crank fine, 3 allso doesnt apply, 4leaking fuel injectors, fuel pump,pressure red ect. 5, fuel not reaching inject, 6 ign componets damp or damaged, 7 bad spark plugs, 8 broken or loose wiring in startin circit, 9 broken or loose wires orconnectors at coils or bad coils. I woulda scanned but myscanner isnt workin. i would check also check park/neutral swith. and maybe a ign switch under the dash isnt getting power to the coils. if all else fails take it to ashop (hate those words and hate saying it) i hope u get her back running.

**19902drlumina** · 03-22-2006, 02:46 PM

where u from maybe someone can help u out if ure close

**Mr Project** · 03-22-2006, 07:06 PM

Thanks, but I'm in Nebraska, so I think there'd be a bit of a commute.

Good suggestions, let me make sure I'm thinking correctly here:

Fuel: The fuel pump comes on(it's new) and I have fuel and pressure in the fuel rail. I think that's ok. I have smelled fuel at times when cranking, though the plugs don't always appear wet when removing them.

ICM & wiring. The old one was tested and was bad. I put a new one in and still no spark. I'll take the new one back today to have it tested, just in case. I have a good signal from the Cranksensor (check with A/C voltmeter), and good power and ground to the ICM.

Spark plugs: Spark plugs all looked fine, very little wear. I saw them all when the heads were off and they looked great.

Spark plug wires: Brand new parts-store brand wires, seem fine. I squeezed the connecters inside the boots to get a tighter fit on the coil towers.

Neutral switch: If the neutral safety switch was bad, wouldn't it refuse to turn over? Is there a test for this?

Is there any way for me to test the output from the ECM?

**19902drlumina** · 03-22-2006, 08:15 PM

well i think ud have to find the wiring coming out of the ecm for the icm controll to test that or have a snap-on scanner hooked up while turning over. about the park/neut switch i think it will also control spark. not sure on that. but if u know anyone with a snap-on scanner scan it

**19902drlumina** · 03-22-2006, 08:22 PM

found this in a search from 3.1 GP Odd no start condition ok, car is a 92 grand prix LE with the 3.1 in it. 205K miles and usually runns great, but lately it's developed an odd nostart problem i'm hoping someone can help me with.
any time the car sitts long enough to cool down. it's won't restart. it spinns over fine and all the electrical stuff works, but it won't fire up. the oddest thing is, if you spray a bunch of starter fluid in the intake, it fires right up and then runns fine. as long as you don't let it sit long enough to cool down, it starts back up fine every time. but as soon as it cools down, no start... i just checked it out and it looks like when it doesn't start it doesn't get fuel or spark. fuel pump primes fine though and there's pressure at the rail. spark plugs look dry though. and with the plug out and connected to the wire there is no spark. i'm a bit lost.. anyone got any ideas??
_________________
his solution. ok, on the advice of a friend i replaced the CPS and it fired up. keeping my fingers crossed that the symptoms don't come back.

**19902drlumina** · 03-22-2006, 08:51 PM

and another search result for same thing explaining the electric

Did they all lose spark at the same time? If so, its unlikely that all the coil packs bummed out at the same time. I'd bet either the ignition module is not getting power and/or ground OR not getting the crank signal. There are 3 connectors on the ICM. The large one is for the ecm to manipulate spark and the tachometer. Then there are 2 smaller ones with two wires each. IIRC, the one on the side by itself carries the 12v and ground signal - a good starting point would be to check to see if indeed that harness is delivering power and ground when the key is in the 'run' position. If that checks out good, then the next step is to check for a crank signal. The two wire harness going into the ICM with yellow and purple wires (they may be color faded from years of heat) delivers the crank signal from the crank position sensor. While cranking the motor you can check for a signal with a digital volt meter. It should produce a low voltage AC signal. If no signal is present then either the crank position sensor has gone bad or the wiring between the CPS and the ICM has failed. The CPS is located on the bottom back side (firewall side) of the block and has a 2 wire harness that is held down by 1 bolt. Be gentle removing it because some become brittle with age and the last thing you want is half a CPS stuck in the block. Don't rule out the wiring though. I just had to run new wiring in my car from the CPS to ICM because at had failed and caused a no start condition. You could simply check for continuity on the wire using an ohm meter. If you end up replacing the wiring it is recommended that the 2 wires have at least 9 twists per foot (as stated in GM service manual) to guard the AC signal from interference

**Mr Project** · 03-22-2006, 10:19 PM

Yeah, thanks, believe it or not I actually did search, I actually printed out that last one you posted and it's been sitting on the hood for the last week.

Just tested:
ICM verified good by parts store test.
CPS is new, and I've seen the AC output on the wires at the ICM.
Wires from CPS ohmed out just fine.
Power and ground to input of ICM are good when key is on.
1 new coil.
Fuses for ignition and ECM are good.

Still no spark anywhere. I don't have a snap-on scanner, is there any other way to test the ECM? I'm tempted to just buy a reman ECM, they run $75 at the parts store. I'm getting into this car pretty deep, though, and I don't want to keep throwing parts at it if I don't know what's wrong.

Starting fluid seems to have no effect, makes sense since I appear to have fuel but no spark.

**19902drlumina** · 03-22-2006, 10:54 PM

b4 u get a new comp get some prom/chips out of same yr same eng car at the j/y i spent 75 for acomp and it wasnt it so try thatfirst b4 u do buy it.

**Mr Project** · 03-22-2006, 11:26 PM

Not sure what you mean. You mean pick up a used ECM at a JY and crack it open to pull out the individual chips and then transplant them into my ECM?

Thanks for sticking with me, btw...I'm getting pretty frustrated with this thing.

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Argh... 3.1 no start condition

Argh... 3.1 no start condition

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