kael

Hey all, bad day.

Started with flushing my radiator. Coolant out, water in, start time. I did disconnect the battery during this.

Battery connected, engine started, ran for about 1-2 seconds and dropped. Haven't been able to get a start since. It turns over fine, sometimes gets the occasion rumble. Other item, the radiator fan is going full boar when ignition is on (before start). Didn't before.

I decided to check for ECM codes, shorted A+B (done this before) and I'm getting zero codes. No 12, no blink at all.

Ugh. Did I mention I have my first Corvette club meeting in 2 days?

Before the coolant flush, Lady ran great, started quickly and no engine problems.

Any pointers?

aklim

Have you checked fuel pressure and spark quality?

Bwbob

I would make sure to check the fuse for the ECM and fusible links etc. Double check any sensors you may have disconnected. I assume you didn't disconnect anything but thought I would mention it in case you had stuff off for bleeding etc.
does the security light blink?

kael

Yep, checked fuses, didn't take any sensors out or even get close to any. Haven't checked fusible links, have to figure out where they are. Would think ECM would alert to these anyway.

Security link does blink, starter does crank. Think I just hit bad luck and ECM happened to go.

I started going through FSM diagnosis today, "chart A-2". So far, all is pointing to ECM or MEMCAL. Just reseated, time for retry.

aklim

You might have better luck finding a solution if you would update your location. Someone might be able to temporarily lend you an ECM to test. I can't because I don't know where you are and my ECM is from a 91 and I don't think it would fit your 87 but someone in that region might.

1993C4LT1

Too see of your ECM is bad, put the key in on the position.

Get a multimeter

Point black probe to a good ground

Red probe to the TPS, ECT, IAT, one at time of course.

You should be getting 5 volts, battery MUST be in good shape

Too high, dirty ECM grounds

Too low, most likely bad ECM


But I agree, I'd check fuel pressure-it's easy

kael

Success!!

I stepped through Chart A-2 from the FSM, had to remove ECM and check MEMCAL. I did the old method, pop the MEMCAL and push back in about 8 times. Re-connect, ignition on....code 12! Remove paperclip and BaBaBaBaROOOOM!! Back to running great!

Now time to finish radiator flush and DRIVE!!

1993C4LT1

Sweet

aklim

Still doesn't tell me why this happened. Anyone?

kael

Update: fix didn't last long.
Little driving in the heat (94 F of course), ECM failed again. SES flicker, no code 12. Poot. Worked a little after cooling, lucky enough to make it back to garage. Time to replace. Hoping the MEMCAL is okay.

aklim: ECM is electronics, 29 year old electronics. Boards age over time, especially when created on 1980's tech level. All it takes is one component or a board trace to stop working, corrode or break. I noted board traces were popped off the board, looked like wrinkles.

Cliff Harris

That's not the traces. That's the solder mask that's put on to prevent solder bridges when the PC board is wave soldered. The heat of the molten solder wave causes the solder mask to wrinkle.

JrRifleCoach

Yeah stay away from those clubs. Unless there's a bunch of C4's

1993C4LT1

I would run the test I mentioned. Unless you already diagnosed.

kael

Finally got replacement ECM. Started right up, hit 210 F sitting in the garage. Couple of short drives (and a loose turn), all good.

aklim

That was what I meant. Why did removing the memcal and replacing it make it work. Seems like you have found the problem.

aklim

Glad to hear it. Congrats. I absolutely hate electrical problems. Especially intermittent ones. They suck the hardest.

JrRifleCoach

Glad to hear your good now.

So next time your washing the car, leave the battery alone.....

kael

Washing the car? Well, maybe the engine....from the inside.

kael

Sorry for not answering yet.
The MEMCAL has a connector, it plugs into the ECM. For electrical connectors, often the metal they are made from burnishes (not quite rust but similar idea) and over a long period of time, the metal connection may get poor or not connect at all.

Easy fix is get that metal scraped a bit, the burnish isn't very thick. Simple method, take the connected items, pull apart then reconnect. Do this several times. This rubs the connectors and gets the metal back to normal state and connection is back to working!

Computer techs, like me, do this all the time with things like memory chips and other items to get a computer going again.