Springster

So I found a pretty cool test to check that the ECM can pulse the injectors.

Turn the key to Run.
Disconnect the 4 pin connector on the dizzy.
Using a test light to limit current, clip one end to 12v and tap the other end on the purple/white wire in the 4 pin connector.
If you have a pressure gauge on the rail you should see the fuel pressure decrease each tap. Otherwise you should hear the injectors click.

This test told me the ECM can pulse the injectors on my car. So I next suspected the ICM (which I had tested twice at 2 parts stores). I checked the pulse output weeks ago but I found it wasn't done right. My scope ground was to the frame and not the black/red wire on the 4 wire dizzy connector. That wire is not "ground" but a ground reference according to the fat book. Either way I got pretty close to the same scope signal. It was not a DC square wave as I was expecting but more like an AC spikey triangle. Anyone have experience on this? Also, I ohm'd the black/red wire to the ECM and got low resistance. So now it seems maybe the ICM is bad? Just thought I'd post an update.

Maverick H1L

iTrader: (8)

Might be a better idea to replace the entire distributor. You can't be sure if the pickup pole piece (AKA magnet) is cracked or not or how good the pickup coil itself is. You do already know your ignition module is probably shot.

Gumby

a pickup coil can half fail and every cylinder will get spark, but every other time.

Springster

Thanks for the ideas! I'll check the distributor pick up pole magnet versus coil output. The scope should show a repeating pattern of 6 pulses and they should look identical. I wish I had the dough to just replace it or know someone with a good one to troubleshoot this weird problem. I confirmed the ICM was ok. See below.

Just to make sure the ignition coil was sparking more than just a short time I put a sparkplug lightbulb tester between the coil and distributor. It kept flashing after the cold start injector fuel was used up. But I have to verify it is sparking for all plugs like Gumby mentioned.

I found a schematic for the 1227170 ECM! http://www.exatorq.com/ludis_obd1/schematics.html

Using this I was able to probe ECM chips and output drivers to verify that the injectors were getting pulsed and I also verified using a clamp-on current probe connected to an oscilloscope. I don't remember or understand why I made the assumption that they were not getting pulsed... I measured 2-3 amp pulses which is about right for three 16ohm soleniods in parallel.

I changed out the fluffy carbon fouled plugs and that made big difference in firing. But it's still only firing off the cold start injector. I know fuel is coming out of the injectors because the rail pressure goes down when I manually turn them on for a split second. I don't know how good the pattern is though. So until I verify the distributor magnet/sensing coil is ok I am stumped. Everything seems to be working. My current guess is that there isn't enough fuel injected to keep it going. Maybe I could use resistors for IAT and Coolant temp sensors to fool it into a colder rich running state...

Springster

The Dizzy checked out ok. There where no shorts from the pickup coil to ground. The pickup coil resistance was in range (I don't remember the value, just that it was within the specs I found). Magnet has no cracks. This car only has 65k on it and parts are very clean, no rust. Engine sounds great when it fires off the cold start injector. "Vroom!, putt, putt ,putt" No missing or chugging. CAT is off. Wife says "Cool!!!", dog runs away. LOL

So I'm back to thinking there is an error in how much fuel is being injected because it fires normal off the cold start and very little or not at all from the other injectors. The Autoxray reports 6-8mS pulses. Anyone know what is typical mS for cranking?

Should the ECM squirt more fuel if I press the gas pedal? Because it doesn't. Seems pretty weird but I don't know how it works... TPS is 0.49v and goes to 4.5v floored.

I double checked the IAT and CTS with a meter. 3.6k for both. Autoxray showed about 65F for both. Exhuast now smells normal using the new plugs. I can't really test the MAF but I have 2, one came from a running car. No difference in not starting using either. And no difference in starting with the MAF unplugged. I would think Limp mode would be used. I even forced Limp mode with a resistor connected to the diagnositic connector. No difference. Calpak or EEPROM bad? No codes are set.


Thanks!

Springster

I tried forcing limp mode by putting a 3.9kohm on A and B of the ALDL. It didn't make much difference.

Any thoughts on the Autoxray data?
-F -E -D -C -B -A T A B C D E F
Prom ID 2891
IAC 130 130 130 122 118 118 118 130 130 130 130 130 130
CTS 58.5 58.5 58.5 58.5 58.5 58.5 58.5 58.5 58.5 58.5 58.5 58.5 58.5
MPH 0 0 0 0 0 0 0 0 0 0 0 0 0
EGR% 0 0 0 0 0 0 0 0 0 0 0 0 0
RPM 0 0 0 1175 300 300 300 0 0 0 0 0 0
TPS 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56
Integrator 128 128 128 128 128 128 128 128 128 128 128 128 128
O2 0.44 0.44 0.44 0.44 0.44 0.43 0.43 0.44 0.44 0.44 0.44 0.44 0.44
MAT 57.2 57.2 57.2 57.2 57.2 57.2 57.2 57.2 57.2 57.2 57.2 57.2 57.2
Load 0 0 0 80 80 80 80 80 0 0 0 0 0
Block Lrn 128 128 128 128 128 128 128 128 128 128 128 128 128
O2 Cross 0 0 0 0 35 35 35 35 0 0 0 0 0
MAF 3 3 3 3 9 9 9 9 3 3 3 3 3
InJ mS 0 0 9.3 9.3 4.6 4.6 4.6 4.6 0 0 0 0 0
Learn No No No No No No No No No No No No No
BattryLow No No No No No No No No No No No No No
Prop O2 Lean Lean Lean Lean Lean Lean Lean Lean Lean Lean Lean Lean Lean
Rich/Lean Lean Lean Lean Rich Rich Rich Rich Rich Lean Lean Lean Lean Lean
Loop Open Open Open Open Open Open Open Open Open Open Open Open Open
Park Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
TCC No No No No No No No No No No No No No
Steering No No No No No No No No No No No No No
4th Gear No No No No No No No No No No No No No
A/C No No No No No No No No No No No No No

Thanks!

Springster

Success at last! Cleaning the injectors to fix the spray pattern got it to stay running!

All plugs indicated carbon fouling from being too rich (fluffy soot). New plugs would foul after 30ish crank/fire/stop attempts.
- I went down the path of MAF reading high but found that unplugging it made no difference. As posted earlier I even went so far as connecting a frequency generator set to 30Hz square wave.
- I next made sure the IAC was opening to allow air to get sucked in and also checked the factory idle screw adjustment (cap was still on meaning it hadn’t been played with). It moved fine and the air path was clean.
- A rare case of carbon soot is weak spark so I bought a tester that has an adjustable gap. I set it to 35Kv and checked at the coil and also at the end of the plug wire. No problem there. By the way, NOTE: The ignition coil is sorta weird. The Secondary will look open if ohms are measured from the post to ground. It is instead connected to B+. You have to ohm from the post to any of the 4 connections on the primary. I get good spark with the coil ungrounded just hanging from the wires. I don’t understand it but just moved onward because I had good spark. Maybe someone can explain this.
- I then pulled the injectors guessing the spray pattern wasn’t atomizing. Rigging up an aircompressor set to 40 PSI I was able to spray carb cleaner through it and got a stream like from a squirtgun. Bad… I brought them to work to look at them under a microscope and found yellowish globs on the pintles (pintle caps taken off). I carefully picked at a glob and it flicked off. Then I saw more in between the injector body and pintle shaft. After running them in a heated oscillating ultrasonic cleaner the junk was out of the shaft area.

So the biggest issue turned out to be bad injector spray pattern, probably caused from varnished gas collecting on the pintles? At least that’s my best guess based on that the car was taken from 6 years of storage and driven 30 miles while slowly running worse then the cat started glowing (unburnt fuel) and eventually would only run a bit from the cold start injector but flood out (maybe) or not fire from the fuel coming from the injectors.

Now I just have to set the base timing, TPS, reset the IAS and other stuffs I found in a Tune up procedure here. Then fix the fallen head liner and bolt the exhaust back together.

So thank you to all who participate on the website. There is a lot of great info here and people with good attitudes! Soon I hope to add to the population of V6 plain jane 3rd gen Camaro RS's still on the road!