TZFBird

Does anyone know of a list of the tests that are run on the ICM and what the different tests mean, or what the failures cause?

I've got a lot of timing and cooling issues. Right now I've got the airdam off and a stainless scoop mounted below the radiator to get enough air through to keep it cool driving under 40. System flushed, radiator removed and cleaned out, etc. I know the cooling issue is due to the ignition system because I've also had to run 350 injectors in the 305 TBI to get rid of detonation just so I can run at a base of 0* otherwise I have to run about -3*. Tested the ignition module and it came back with a failure at 'Low RPM'. Had another I was going to try that I snagged at a yard and it failed for 'Bypass'.

I'm going to try and run that one with the 305 injectors back in it and see what problems 'Bypass' causes.

Before anyone criticizes for trying this, I have the new engine sitting and ready to go in the car. I just want to get all this worked out before I switch the dist. over and any sensors that might be causing this problem.

Sonix

iTrader: (1)

I know very little about how you would test your factory TBI ignition module.
However I do know a bit about cooling. I think that with a good cooling system, it's virtually impossible to overheat the car with low load (idle, around town, etc).
Can you describe, or show pictures of your air damn setup? I think you may be fighting the original engineering behind the concept of the air dam?

naf

iTrader: (7)

If his timing's screwed up it will overheat in a heartbeat, especially if it's severely retarding the ignition. Less efficient combustion means it requires more fuel for the same amount of power. All that extra fuel still burns-just not in the sweet spot of the power stroke. Same deal with a rich condition. He's likely got both.

A new ignition module isn't much $. Even a generic one from AZ will work.

Are you testing the modules out of the dist?

TZFBird

Yes, I took it out and to the parts store where it checked out bad on their machine. It obviously puts 12 volts to the module, and must give signals similar to that of the pickup on the distributor, then checks the output that would be sent to the coil. From there I suppose it can tell if it's good by the rate of input pulses vs. the rate of output pulses. As far as what ever else these things can do I'm not sure.
I know the timing is/was the problem with cooling.
I might swing in the store again and make a list of all the checks that the machine performs. Really, for all intensive purposes, the module is just a relay that is capable of switching thousands of times per second.

naf

iTrader: (7)

The 'relay' does a little more than that. The module will also provide rudimentary ignition advance when not controlled (disconnected) from the ecm.

Parts store sell you a new one? The last AC Delco module I bought had 'made in singapore' on the back so I'm not as hot as I used to be for original AC Delco parts.

TZFBird

I havn't bought a new one yet.

I'm just not sure how these things can do what they do and only cost $30. I work electrical maintenance, there are electronics that cost 20 times that, do less, and don't last as long. I just find it a bit hard to believe that these can do as much as it may seem.

Oh well, not that I'm complaining because I would sure hate to pay $600 for an ignition module.

GMODUDE

iTrader: (2)

I have the solution to the ignition control module for you. This is a very true story. I work at Napa in NC we have an actually kit that can chek hundreds of types of modules. I just chekd mine the other day matter of fact. I can get the list off the machine for u there r 5 things it cheks i know 2 off my head one is high rpm and low rpm. i can get the rest later but if I were u and dont wanna waste ur money ide chek at a local napa it takes literally 5 min to chek u take ur module off they plug it in and boom tells u if its good or bad. Really handy and is sweeeeeet instead of wasting ur 30$


Rofl my bad only read the first part of the thread . sorry

TZFBird

Well, swapped in the module that tested bad for "Bypass". Switched back to the 305 injectors. Ran the car around the neighborhood until all warmed up, then took it out on the highway for a full throttle run. Ran like a top, not a miss or any detonation(sounded like someone dropped something metal down the intake and made it into a cylinder). I'm still going to get a new module though.

TZFBird

Sonix, here's a few pics of the airdam I have on there now. It's not doing to bad, but I do have some more plans for it as soon as I get an engine back in the car. I failed to get a side shot to show the scoop that I have rolled into it. It's as wide as the radiator though and sticks down as far as the factory air dam does including that softer strip at the bottom.