I'm pretty frustrated with the progress of the ignition problems w/ my "93 coupe. I've got fire at the points and plugs, but it won't start. It seems it tries to start(maybe weak at the plugs). A deterioration that went on for a week or 2, where it got harder and harder to start. I've replaced the opti numerous times over the past few years. The last time I put a MSD cap and rotor on a new GM opti. I got a couple of hundred miles out of it this time. Not to mention power steering pump and a new fuel pump. I had convinced myself the rotor had come loose inside the distributor. MSD warns about that. So I tore it down this weekend. Rotor looks ok. I replaced the wire bundle from the opti up to the right side of the engine, and put a new ICM in. Still won't start.

It's been 4 years since it sat up in storage for a year and a half, didn't have $ to fix it. It ain't been right since. Service ASR/service ABS stays on always. No codes. I'm seriously thinking ECM. I have an advantage of being able to check the opti out of the car now. Sure would be nice to get to drive it some. Any thoughts or ideas?

 

Check the injector pulses with a noid light to see if the injectors have drive. If you do, that would indicate the opti's optical portion is working because it is driving the ECM. Then the ECM would be basically working if you had spark and injector drive.

If that was all good I would then pull the injectors and see if they were spraying. Maybe they are partially clogged.

The ABS codes come from the brake computer (EBTCM) not the ECM and that is module 9.0 You might try clearing module 9.0 using 9.7 function. Taking off the battery cable won't clear it.

 

Do you have 12.3 - 12.4 volts at the battery? Or is it starting to run down?

 

I neglected to mention that I have tried to spray either down the throttle body, and it does't try to start. Time to invest in a noid light, as changing the ECM would be expensive, I've never had the injectors out. Time to read up on that process.
Battery voltage could get weak after turning it over some. Usually I charge a battery all night. So I start off with a well charged battery. I could try another battery.
Thanks for your suggestions PColt.

 

I would start all over, treat it as a no start. Do you have good fuel pressure? Does the pump run for 2 sec. at key On, check with gauge too. Good solid blue spark at plugs? Check inline from coil to opti wire with inline spark checker as well. (Harbor Freight has these like less than 5 bucks). Spark should be regular as well.

Noid lights are cheap too...parts store might even have some available for rent.

The fact it has been sitting....just because they are NEW parts does not mean diddly crap. I see new (mostly aftermarket) parts fail all the time.

 

There is about 50 lbs. of fuel pressure on the gauge. Coill has such a good spark that it jumped from the coil to the chassis once when I forgot to hook up the tester. At the plugs, it's there, but not as hot as the coil. That's what made me think ICM. The spark at the plug is of nonmeasurable quality. I wish I knew if it were suffecient. In my experience any fire should try to start somewhat, especially with highly flamable either in the compustion chamber.
I hear what your saying about buying bad parts. I just wish I knew what part.
I prefer to gamble in a casino.
Thanks for your input.

 

The ICM drives the coil. If you have that much spark off the coil, then all being equal it does not sound like the ICM is your problem. Only you can determine if there is enough spark at the plugs. Nobody else can see the spark.

But the only thing that comes to mind is to make sure the coil wire to opti is not breaking down and sparking to the water pump where it goes thru it.

 

You said it sat for 41/2 years. That gas isn't that old is it? Just a thought.

 

The first time this happened I was between jobs, and broke, so rather then fix it, I put it in storage for about a year and a half. After I returned from working far away, I got it out of storage. It's been a series of "one thing after another" starting when I got it out of storage. It's ran for a week or 2 tops, then something else breaks. I'm thinking I got everything else this time, but this ignition problem has been ongoing for too long. A real bear. So the total time since the car was put in storage was about 4 1/2 years.

 

Have you pulled a few plugs and wires to look at plugs and put an ohm metter on the wires. If all that stuff is over 4 or 5 years old I would consider changing them if the spark is very good at the coil wire and so so at the plugs.
Dave

 

I tested the injectors electrical with a rented noid light this week end, NO FLASHING. I cupped my hand around it to make things dark, nothing! The only injector unplugged at the time is the 2nd one back on the passenger side. I'm thinking ECM. Do you agree? What is a good economical fix? Thanks!

 

I would check 2 additional items. Make sure you have 12 volts on the injector terminals when the key is turned on. And make sure you had the correct polarity on the noid light when installed. If you connect them backwards, they will never light even if the pulses (drive) is there.

Have you tried putting some fuel in the intake to see if it would start and run a bit.

 

The noid light is difficult to insert in one polarity. I got it in there. No flash when i spin it over with the key on. Both leads of the fuel injectors come on when the key is switched on. I measure 10.15 dc volts on either lead. These go to zero when the key is switched off. I am of the opinion that this problem has been ongoing and is intermitten. Thanks for your help PColt. Where to next?

 

If you are measuring 10.15 volts on the leads of the injectors with the key ON, that does not sit right with me. That voltage comes from the battery thru ignition switch and fuses and is an un-loaded voltage and should be very close to the battery voltage (within a couple tenths of a volt). Unless you battery is under 10.5 volts, 10.15 is just not close enough to 12 where it should be close to.

If the battery was 10.5 volts or so, cranking it over I would expect it would be slow or not at all. If your battery is 12 volts and fully charged check fuses #22 & 23 (inj1 & inj2). Check to see if you have 12 volts on one of the fuse leads itself.

This voltage comes from the ignition switch to the fuses. If the ignition switch is bad, it could be causing insufficient voltage to the injectors.

You need to confirm and rectify proper voltage to the injectors before you jump to the ECM.

 

I measure 12.7 at the battery terminal, so there is a voltage drop somewhere. I will try one out of the wifes pontiac battery after work, also will check the injector fuses. Thanks for your assist.

 

The ECM won't fire the injectors unless it sees reference pulses from the ICM. It uses them to synchronize the injectors to the ignition.

Have you pulled error codes?

 

You will get power on both injector leads unless you unplug all the injectors on the bank you are checking as it feeds through the other injectors.

Check power at the ecu while cranking. Ceck for a signal from the ICM to the the ECU. If you were to rent of buy one tool it would be a good scantool that can read live data and stored codes. They can be had on various auction sites or user forum sales pages. I bought on for my 91 the same week I bought the car as I consider it essential and a big timesaver if there is a problem. If you spayed starting fluid in it and no run or try to run I would have to suspect an ignition problem of some sort. It could be bad plug wires plugs cap rotor or timing. You can easily put a timing light on a plug wire and see if it flashes. A lack of a timing mark on a LT1 is a real issue for me as a valuable iagnostic tool as you could have a great spark and if for any reason at the wrong time a no run situation.

Dave

 

Almost correct, but just want the clear up one wrong word so it won't confuse the others who are trying to learn. It should be OPTI not ICM.

Should be:
The ECM won't fire the injectors unless it sees reference pulses from the OPTI. It uses them to synchronize the injectors to the ignition.

To just say it simply, the OPTI drives the ECM (PCM), the ECM drives the ICM and the injectors, and the ICM drives the coil. Then the spark from the coil goes back to the cap of the opti like any other distributor.

 

Is the engine actually running now and backfiring? I would recheck the plug wires to make sure none are crossed and are going to the right places.

Did the opti just slip on with ease (slight push) and contact the cover. The bolts only hold it and should not be used to draw the opti to the engine.

You actually could pull the opti with ease to check the alignment of the shaft if you have any question if it's right or not.

If you are running with no water pump, you need to connect the ECT sensor in the pump to the connector. It will start but will not run without it hooked up. You can just lay the pump on the rubber intake and pull the wires up, they will reach the pump. Then you can run the engine with proper A/F mixture.

 

This weekend I took the opti off, very careful to get the marks on the gear lined up. First in the block (I wanted to check that too) Then the distributor. This time I had the cap removed in order to turn the shaft, via the rotor in small increments until it slipped in flush. Carefully taking time to check the wires for proper firing order. I found a few with a little rust on the opti connections, cleaned each one up til it was shiny new, and rechecked each one again for rust, and cleaned if nessecary. That only appeared on the driver's side. Only 2 or 3 like that. I put in a fresh hot battery from my mom's oldsmoble. It sputtered, and finally started up after I pumped the gas pedal. It seemed to even out after a minute or 2. All I want to run it with no water pump. I feel I'm not out of the woods yet. I plan to start it again after dark to look for arcing over. I'm thinking plug wires. I pulled one plug an it was clean as a whissle.
What's been the history. After a tear down it will run for a week or two then quit. Something intermitten. Every other time I've had problems w/ this car it was very good at giving me codes, a starting place to look. But not this time. I still suspect a bad ECM. My moms olds quit running. Also a '93 GM product. ECM was replaced and its run great ever since.