Well, if you have no spark, I wouldn't automatically assume that you have a bad ECU.
You need to start from the bottom and work up.
Your car runs DIGIFart fuel injection. Fuel is metered by the ECU. On the old CIS systems, fuel flow was continuous and mechanical. On DIGIFart, fuel flow is metered by electronic injectors (true EFI), and pressure is regulated by a diaphragm on the fule rail. Fuel pressure is not as important on the DIGIFart as it was on the CIS, and the injector valves open under electronic control, rather than increasing fuel pressure. The amount of time the injectors are open, is a function of the air flow (measured by the MAF), engine temp (measured by the sensor), and the amount of oxygen in the exhaust gasses (O2 sensor).
Operationally, it's a pretty simple system. However, the ECU's and MAFs can easily screw up operation. The ECU was the most common failure point as noted by others, due to the problem with ground wires. Once the wires broke or lost contact, the ECU essentially was fried.
The ignition however, was a completely separate entity. Not until the MK3 (with a crank position sensor) was ignition timing completely controlled electronically. Up to 1992, the distributor worked just like a normal vacuum advance dist found on most cars. On the CIS, the advance was controlled by vacuum, with spark distribution controlled by the Hall sender and the ignition control module. The Hall Sender (integrated into the base of the dist., and where the plug comes in), essentially works like the 4 raised ridges would on a points and condenser type distributor. The 4 "windows" on the rotating "cam sensor" tell the coil when to fire. The signal is sent to the ignition control module (usually mounted to the ECU, or nearby under the rain tray), which sends the signal to the coil, which sends an amplified spark signal to the plug.
On later models, an ignition "Knock" box and knock sensor were added. Essentially, these controlled the advance, rather than the old vacuum canisters. Even with this advancement, the ignition was independent of fuel control, which was handled by the ECU, and there still was a vacuum element to the advance (remember the old knock boxes with a vacuum hose attached?). ON the DIGIFart, the vacuum element was tossed, and advance was controlled electronically.
Thus, if you are not getting spark, it means you have a problem in one of those arenas: the distributor, the coil, the ignition control module, or the knock box.
The knock boxes rarely go bad, so you can probably rule that out.
Hall senders do go bad. Especially on the Digifant
The ignition control modules rarely go bad.
The Coils rarely go bad.
What you first must do is the following (all of this is outlined in the Bentley manual)
1) Check your grounds. The ignition system usually has its own harness with its own ground wire. Without ground, it won't fire. ALso, check ALL OF YOUR GROUNDS, including the main one which connects the battery to the body, and then to the transmission.
2) Check that you have power to the coil 2. This usually involves checking for voltage at the #1 and #15 terminals on the sides of the coil. If you do, it generally means the ignition control unit is fine, as is the Hall Sender.
3) Check coil resistivity
4) Make sure you have the correct plug into the Hall Distributor (the plug on the side of the dist), and that it's fully engaged (I had that problem once).
5) Check the other components (cap, rotor, plugs, wires, etc).
If you have spark, but it's weak, then you have a bad coil. If you have no spark whatsoever, I'd start with the distributor, specifically, the Hall Sender.
Once you have spark, then look at the fuel system. I wouldn't automatically assume the ECU is bad just yet. Chances are good, but you need to sort out the spark issue and then move forward.
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