Help getting SC3800 swap troubleshooting (Page 2/3)
KissMySSFiero FEB 28, 11:57 AM

quote
Originally posted by olejoedad:

The ICM controls fuel delivery at initial cranking, and sends a voltage signal to the PCM to initiate the PCM fuel injector drivers.

Have you tried replacing the ICM?



Thanks for helping, I posted in some facebook groups and too many look past the fact that I said the car runs. They proceed to tell me to replace the fuel pump. Then people argue and chaos ensues.
yes, I forgot to mention that there have been at least 4 ICM's installed, one being new.

All acted exactly the same. Statistically unlikely that they all were bad in an identical manner.

I've also checked connectivity to every wire I think is related to fuel control/delivery and the ICM. I don't have the paper in front of me to see what I checked.

here is a guide I was using for some troubleshooting.

https://easyautodiagnostics...-crank-sensor-test-1

It's mentioned where the ICM controls spark at cranking and below 400rpm. I assume it controls the injectors as well.

I have spark, obviously it starts on starting fluid. But I did verify spark.

My thought is that it is still able to control spark. But not fuel until it hits 400rpms. when starting fluid initializes the cranking, it exceeds 400rpm and the ECM takes over fuel control.

But the new ICM acts just like the previous 3. The previous owner obviously went down the route of trying the ICM because there was an extra ICM and an extra with coils.

I do believe he changed the CAM sensor because I have the old one in the box of extra parts. But I don't think he actually changed the crank sensor. if he did, it looks like it's been on the engine awhile and I can't imagine putting in a used crank sensor when a new one is Delco one $30. Plus it doesn't look as easy as the cam sensor since you have to pull the balancer.

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KissMySSFiero FEB 28, 12:03 PM
Here is a pinout I've been using for reference.
olejoedad FEB 28, 12:23 PM
Have you spoken to Ryan at Sinister Performance?
OldsFiero FEB 28, 06:55 PM
Sounds like an issue with the bypass circuit (tan/black # 424) to me. Try to back probe that terminal at the ICM connector and connect it to ground. If it starts, remove the jumper from ground and connect to your meter to see if you have 5V . If not, you are running at base timing. I'm not sure if the bypass circuit in the ICM is Hi z or not but, if it is a lack of a 0v there when cranking, that could do it. If you see 5v running and more than 0v cranking, I would suspect the ecm.
KissMySSFiero MAR 02, 11:49 AM

quote
Originally posted by olejoedad:

Have you spoken to Ryan at Sinister Performance?


Yes I have. I'm using his for my LS4 swap tuning as well.


quote
Originally posted by OldsFiero:

Sounds like an issue with the bypass circuit (tan/black # 424) to me. Try to back probe that terminal at the ICM connector and connect it to ground. If it starts, remove the jumper from ground and connect to your meter to see if you have 5V . If not, you are running at base timing. I'm not sure if the bypass circuit in the ICM is Hi z or not but, if it is a lack of a 0v there when cranking, that could do it. If you see 5v running and more than 0v cranking, I would suspect the ecm.



So I started by reading this.

https://www.3800pro.com/thr...m-description.34200/

Then I started taking notes on what I'm checking

I did contact Ryan Gick. He said that to measure the voltage on the injector pin, it needs to have a load and it should have 12V on each pin.
I verified this by measure with the injector plugged in and inserting pins on the connector to make contact.

12v on each injector connector pin.

on the cam and crank sensor, I get 6.7V on pin G/H/J of the ICM. This was what I expected. Approx 7V.

I see 11V on pin N of the ICM, sensor feed out. Should be 10-12V

12V, battery voltage on pin P of the ICM.

I attempted grounding the Bypass Pin B of the ICM and starting the car. It would not start.

I started the car with starting fluid. Then grounded the bypass and could hear the timing change. I have a OBD II scan tool app on my phone. I can monitor timing. It dropped from 24 deg to 19-20 deg.

Upon stopping the car, and restarting, it stayed in bypass mode and the observed timing was 10.0 deg. But I was able to start the car the car without starting fluid.

I did not see any voltage on the bypass circuit. The car would not come out of bypass. So by removing the circuit from ground, timing stayed at 10deg.

I had to turn the ignition off for a decent amount of time to get it out of bypass. 5 seconds or less was not enough time. It stayed in bypass.

After it came out of bypass, it could not get it to repeat by grounding the bypass circuit. But it would also not start again with the timing at the original 24degrees. Now it's stuck on 19-20degrees.

It's possible I damaged something. But I'm clueless at this point. I have a general grasp of how the ignition system works.

by the video I posted above,


quote
Originally posted by a chitty mechanic:

https://youtu.be/jACyNHl_L1g?t=621

I'm seeing 4.5-5v average on the 3x signal and less than 3v avg on the 18x. Where it should be appox 5.5v and 4.5v respectively.



I need to recheck these voltages. I thought I was dropping voltage in the harness from the ICM, through the sensor, and back to the ICM, but I'm seeing what I think it should be, 10V input and 7V output. And each of the 3 circuits are seeing the same 6.7V. That's with the engine off of course. The interrupter ring turns the 7V on-off-on-off... reducing the average voltage for the 360 degree rotation. Seen as a square waves.

I ordered a cheap handheld digital O-scope. It was $40 on amazon so I'll be able to freeze the signal and look at it better. Maybe something is off that I can't see on my old oscope.

I only get about an hour in the evenings if I'm not already exhausted from work and life.

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SSFiero@Aol.com

KissMySSFiero MAR 02, 12:32 PM

quote
Originally posted by MichiganReefer:

I'm just spitballing, but have you checked the individual resistances of the injectors? Google is telling me they should be reading 12 ohms +-.6.



Resistance is 12Ω +-0.5, so normal.
Thanks
KissMySSFiero MAR 02, 12:34 PM

quote
Originally posted by Frenchrafe:

Wiring problems? (Lots of continuity checking!)
If not, then which PCM are you running?
I've had a '95 PCM go compleatly bonkers!
I changed and repinned for a later '98+ PCM. No more problems afterwards😉




It's a '98+ PCM. I'm not ruling out a wiring issue. But I've check continuity on any circuits I think could be related and then some more.
I could have a short between circuits, But that's something I'll check if I have to pull the drivetrain before getting it running right. It's coming out for a clutch anyway.
OldsFiero MAR 04, 07:32 AM
I don't think grounding the bypass circuit would cause damage, but that's not to say you don't have a problem with the board. Another thought; have you checked supply voltages at the PCM while cranking? Might want to headlight bulb test powers and grounds at the PCM connector, if you haven't already.

I see that it's a manual trans. Just for grins try shutting the car off on a grade where it will roll and try pop starting it.

Marc
KissMySSFiero MAR 10, 08:12 PM

quote
Originally posted by OldsFiero:

I don't think grounding the bypass circuit would cause damage, but that's not to say you don't have a problem with the board. Another thought; have you checked supply voltages at the PCM while cranking? Might want to headlight bulb test powers and grounds at the PCM connector, if you haven't already.

I see that it's a manual trans. Just for grins try shutting the car off on a grade where it will roll and try pop starting it.

Marc



I live in FL we don't have grades. But I did kill the engine, then roll start it several times.
I bought HPTuners as well for the VCM scanner(among other things)
While roll starting the car, I still need to see over 800rpm before the injectors pulse. Cranking with the starter only sees about 200rpm.
While cranking, I'm seeing just over 11v at the PCM battery power and slightly lower at the PCM hot in run pin.
I don't think it's a battery voltage issue.

Tomorrow I'm going to start pulling the drivetrain for the clutch swap.
So I'll be able to inspect everything and button up a few things I don't like about how the swap was done.
I can also do continuity checks on all the PCM connections.

One thing is for sure, I will figure it out.

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SSFiero@Aol.com

olejoedad MAR 11, 12:30 AM
Check circuit 430, fuel control (out) for continuity, bent pin etc.