Troubleshooting Ignition Control Module ???

[nkemp]

Original problem solved (user error). But it still begs the question about troubleshooting an Ignition Control Module/unit.

[David T]

Original problem solved (user error). But it still begs the question about troubleshooting an Ignition Control Module/unit.

You rule out all other possibilities before assuming the ECU is at fault. Refer to M:01:03-:04 in the Workshop Manual. Just an FYI, it is rare to see an ignition ECU fail.
David Teitelbaum

[DMCMW Dave]

Original problem solved (user error). But it still begs the question about troubleshooting an Ignition Control Module/unit.

Replace with a test unit. The car still won't run, then you put the original back in and figure out the problem.

But really, if everything else tests good (resistance/continuity to the pickup coil, power and ground) the only real, final, test is a substitute part.

[nkemp]

A replacement/test unit sounds like the best way.

I think I have my intermittent dying problem solved. But I now drive the car with a bit of concern and worry. Recently I saw this elsewhere... "A failing ignition control module can be a real headache at times. It can produce a wide range of engine performance problems, including preventing the engine from starting or stalling the engine as you speed down the road, just to let you resume your driving a few minutes later, as if nothing had happened."

I think my problem was inertia switch or ground related.

Thanks for the input,
Nick

[dmc6960]

Dont forget Nick that there ARE a small handful of local DeLoreans active and driving. If you ever needed to borrow a part I could easily stop by sometime.

[AugustneverEnds]

Here I am dusting off older threads again but I am starting to think my ignition ECU is dead. I have been troubleshooting an ignition issue for a month now (working slowly and on several projects) and I have run out of anything else to try. Besides being the last item on the list I read here on the forum that if the tach doesn't move when cranking the ignition ECU becomes a suspect. I tested the plug to the ignition module with an icepick light and it is getting power. Fuse 1 is good. My car is a high mileage (100k+) car so maybe the module is toast?

Would it be possible to call a vendor and perhaps put a deposit down to borrow an ECU to test? I have read some owners are using Ford or GM modules. How are Autozone or Advance with returning electrical parts? I don't want to buy one and not have it solve the problem and be stuck with it.

[mr_maxime]

Would it be possible to call a vendor and perhaps put a deposit down to borrow an ECU to test? I have read some owners are using Ford or GM modules. How are Autozone or Advance with returning electrical parts? I don't want to buy one and not have it solve the problem and be stuck with it.

I've got one. PM sent

[David T]

The best trouble shooting chart is in the Tech Manual pages 125-126. If you don't have it the most common problems are;
Not using an OEM Bosch ignition coil
Bad pick-up coil or bad connection
Low system voltage (must be higher than 11 volts!).
Bad connection on the ballast resistor, the connections get rusty.
Bad wires, cap or rotor.
The place to start is to see if you get spark out of the coil while cranking. The ECU is the LAST thing that fails. Very rare.

[nkemp]

... How are Autozone or Advance with returning electrical parts? I don't want to buy one and not have it solve the problem and be stuck with it.

Electrical parts are the parts many places won't take back if installed. Too easy to ruin them if there is some other electrical failure.

[AugustneverEnds]

The best trouble shooting chart is in the Tech Manual pages 125-126. If you don't have it the most common problems are;
Not using an OEM Bosch ignition coil
Bad pick-up coil or bad connection
Low system voltage (must be higher than 11 volts!).
Bad connection on the ballast resistor, the connections get rusty.
Bad wires, cap or rotor.
The place to start is to see if you get spark out of the coil while cranking. The ECU is the LAST thing that fails. Very rare.

Replaced the original coil in 2017 with an OEM Bosch coil. It's getting power and measuring .6 Ohms primary resistance
Bought a new battery a few weeks ago, reading 12.5 Volts
Replaced the terminals on the ballast resistor
Wires, cap and rotor replaced in 2017 (Bougicord and whatever PJ Grady sent to me),,

Hmmm pickup coil.... What test would rule that out? Like I stated earlier, I saw no spark on one of the plugs and the tach is not moving

[AugustneverEnds]

Electrical parts are the parts many places won't take back if installed. Too easy to ruin them if there is some other electrical failure.

I thought so. I got stuck with a lamp control module for a BMW when it turned out to be a different problem.

[dn010]

How do your bulkhead connectors look? I know I've said it many times on this forum and it may not be your problem but it doesn't hurt to check. Those connectors are garbage and gave me nothing but problems until I cut them off and replaced them with a weatherpack. They're especially worse if you've run without a coil cover. Check to see if you have corrosion, I used to have to take a dremel with a small bit to clean the corrosion off the female ends and bend them in a little to make a solid connection. These connectors caused me to have all sorts of issues with the engine as well as the tail lights.

[AugustneverEnds]

How do your bulkhead connectors look? I know I've said it many times on this forum and it may not be your problem but it doesn't hurt to check. Those connectors are garbage and gave me nothing but problems until I cut them off and replaced them with a weatherpack. They're especially worse if you've run without a coil cover. Check to see if you have corrosion, I used to have to take a dremel with a small bit to clean the corrosion off the female ends and bend them in a little to make a solid connection. These connectors caused me to have all sorts of issues with the engine as well as the tail lights.

Those connectors are garbage and a PITA! I just finished fixing the yellow one, pushed in terminals were the reason the cooling fans were not turning on with the otterstat. Besides those everything else seems to be working.

The connector between the distributor and ignition ECU is intact and corrosion free.

[AugustneverEnds]

10287 has awaken from its coma!

I dug through my spare parts stash and found the extra ballast resistor the PO included. Out of curiosity/desperation I put it in and now we are running! :neener:

How the hell often do ballast resistor fail???

[David T]

They are very brittle and can crack but the common failure mode is just bad connections. The connections are steel and they rust.

[Bitsyncmaster]

I found the ballast resistor tabs to be stainless steel (I could not solder the wires to them). The heating puts a lot of stress on the wire connectors.

[AugustneverEnds]

They are very brittle and can crack but the common failure mode is just bad connections. The connections are steel and they rust.

Before I tried replacing the resistor itself I cut off the old, original connectors but it didn't fix the problem. More than anything the only reason I swapped the resistor was because I remembered I had an extra sitting around. I didn't expect it to change anything but it seemed more productive than cursing and being pissy. The two resistors look identical and feel the same in my hand, can't figure out what the deal is with the first one. Couldn't have been more surprised when the car started.