Zootal

It was time. The door panels were falling apart, the paint badly peeling, the passenger side wheels both bent (cause my wife likes to hit curbs when turning), the rear end needed to be rebuilt, cat was shot, bad oil leak from back of engine, heavy oil burning...the list goes on and on. I was considering fixing these things, but this was the last nail in the coffin... It was a good car. Our new Subaru will probably not last as long - I wish I could get another car just like this only 20 years newer...

As I mentioned in my other thread - I finally gave up. I load tested all the power and ground wires, I tested every wire and sensor. Nothing is wrong. I finally decided the ECU was bad, the replacement was bad and my chances of getting a good one is not worth the $200 bill it would cost to try again. I retired the car. **sobs Donated it to Veteran Car Donations. Maybe someone will find some good parts in it... **sobs...

I actually went in and replaced the electrolytics. Sadly did not change anything. I checked every wire and every sensor that connects to this thing. Eventually I decided to stop throwing time and money a this car, and retired it. **sobs I've had that care for 20 years... **sobs... I still miss it. My wife has a 2016 Subaru. This old Legacy was a much better car.

FWIW, I want to thank all of you that have contributed to this thread. Your comments helped me think more clearly about this and prompted me to test a few things I would not have thought to test. This has got to be one of the best gathering points for Subaru expertise.

I actually opened it up and replaced the big electrolytic capacitors - there are four of them. Sadly, it made no difference. They were clean, dry and not bulging. I have a cap checker in a box somewhere, I might dig it out and test them just out of curiosity. Traditional wisdom says electrolytics don't last that long, but I've got 40 year old electronics with electrolytics that work just fine <shrug>.... I like the car, but where do you draw the line and stop spending money on it? Honestly, this car has cost me a small fortune in maintenance. Just about every small part that can go bad has - starter, radiator, p/s pump, it's on its third alternator, front steering rack, weird a/c problem that cost $500 to fix. The only thing that has not (yet) gone bad is the a/c compressor. OTOH, we are not in a position to replace it right now. I'm thinking of getting one more ECU just to make sure, before I make the decision to send it to the junk yard. I watched the ground and power in while it was glitching. It was as smooth as can be. My load tests to the power/ground leads showed them to be clean. And yet, turn on the key, and the injectors start chattering, fuel pump starts cycling and I'm wondering if there is a poltergeist living in it? For now, it sits in my garage while I think about it....

Just did. Jury rigged a 5 amp load (three tail light bulbs lol) and verified it draws about five amps. Tested every ground and every supply pin, and all of them are less than .1 volts from battery or ground. Well within tolerances. Dang. I think the ECU is bad. What else is left? The sensors are disconnected, and what is still connected is verified working with good wiring. I think these old ECUs just go bad eventually and I bought a bad one. I'm tempted to try yet another one, but that is a hundred dollar bill just to get one from another junkyard with no guarantee that it is good...<sigh>...

I thought of that - I once had a bad power supply blow a mother board, and I didn't realize it was the power supply until I put it into another computer - zap, two blown motherboards, but I digress... I thought I was pretty thorough when checking the connectors at the ECU, I checked voltages/grounds with it running, and then I pulled the connectors and checked continuity. Everything was as it should be. I disconnected just about everything I could, sensors, etc. Disconnected wire harness plugs leading to instruments, removed tranny control unit (cause it was in my way), unplugged everything I could. Still - turn the key on, and injectors and fuel pump cycle intermittently and after a few minutes, almost as if on a timer, the radiator fans turn on and won't turn off until you turn the key on. Oh this is even better - if I turn the key on again the fans come on immediately. The only way to get them to stop coming on is to put the ECU into test mode using the test connector, and then disconnect it. Fans shut off - until next time the seemingly randomly turn on again. I really don't know where to look next, or wtf is going on. Maybe these ECUs just do that after 25 years? 25 years for an electronic device is pretty remarkable. *Everything* I've done points to a bad ECU. It is, after all, the ECU that fires injectors, cycles the fuel pump relay, pulses the tachometer. The ECU controls all of this, and I don't see any power/ground or input problems, in fact it does this with most of the input devices/sensors disconnected. Retiring the car is approaching the top of my list - 25 years old, 230,000 + miles (or is it 280,000?). Burns oil, tranny shifts hard and whines, paint is peeling badly, visors broken, door panels peeling, seats need reupholstering. It looks like hell. Leaks oil, needs rear struts and brakes....driver side front auto seat belt doesn't work, drivers door doesn't shut right (cause it was wrecked and not fix right many years ago). It really is falling apart, and this is kinda the last nail on the coffin... Ok, sorry, I'm thinking out loud and venting....it's been a long day crawling under the dash

Well I think I'm done with this car. I traced the wiring to/from the ECU, checked voltage/ground at the pins, and there is nothing wrong. It has power, it has ground, most of the sensors are disconnected and what is connected is working fine. Everything points to a bad ECU, but I replaced the ECU and it's doing the same thing. What are the chances of the replacement ECU being bad? Even pulled the fuse block, inspected everything I could find to inspect, measured resistance from ground pins to chassis ground, checked b+ at power pins, checked the wiring for the sensors to make sure none of them had problems. There just isn't anything wrong that I can find. There is one pin labeled "Self-shutoff control". I'm not sure where it goes because I did not want to cut open the wire loom and trace it, and I don't see it in the wiring diagrams. Anyone know what that does?

Here is an update for anyone following this thread. 1) Replacing ECU did not fix problem. 2) I have discovered that just about any mild surge to the electrical system - turn signals, honking horn, etc. - causes the fuel pump to cycle and injectors to chatter, injecting fuel into a non-running engine. It frequently does it by itself, but I can easily trigger it just by turning on turn signals for a second. I can start the engine and it runs, even drive it, but it's a bit rough. I have unplugged most sensors under the hood, unplugged the fuel pump relay and put a test light across it so I can have a visual indicator of this happening. Today I'm going to drop the ECU and check all power and ground connections, and then all inputs and outputs. Why oh why did they shove it up under the dash where you can hardly get to it? I'm going to remove driver seat so I can at least lay down and get comfortable while doing this. I'm tempted to pull the instrument console just to see if it gives me better access to the wiring.

So if I unplug the alternator, the symptoms stop immediately. I can then start and run the engine and *everything* is perfectly normal (except it won't charge because the alternator is unplugged). I plug in the plug on the top of the alternator, and the computer immediately starts to cycle the fuel pump relay and the injectors. I'm going to trace the wiring from the connector to see if there is a problem there, or where it goes... Yes I tested the alternator, - auto parts store says it is good. I'm not 100% satisfied, but I need to examine wiring diagram and inspect related wiring before I'm ready to invest $$$ in an alternator that might not fix the problem. I mention this just in case this rings a bell with anyone...

Found wiring diagram for alarm - all it does is disable the starter. Pulled fuel pump relay and put test light across the pins that actuate the relay, and sure enough, it toggles on and off intermittently, ever couple of seconds. I think I'm going to end up doing this the hard way, tracing wiring into the computer and trace all the inputs and outputs. *Something* is causing the ecu to do this. It's a real bear to get up under the dash to the wiring <sigh> I think I'll pull the instrument cluster and see if that gives better access...

I think you are right about the fuel pump relay, and I think the ignition also goes through the alarm. It is supposed to shut things down if it thinks someone is trying to steal the car. I wonder if power to the computer also goes through it? I think tomorrow I'll take a closer look at the alarm box, see how they hacked it in, and see what goes through it. At least it's in the open and easy to get to, and if the power to the fuel pump relay and other things goes through it, I should be able to find it....thanks for being a sounding board, it's as good of an approach as any...

Here is another though - could the alarm controller cause this? It's not causing the relay click sound, it's actually hanging by a bunch of wires on the floor because I haven't tucked the wiring back under the dash. But could a bad alarm controller be the culprit? It's an aftermarket, forget the make. I think they are still available and don't cost that much.

Replaced computer. 1) Pulled spark plugs.One hole was flooded, I turned the engine with a wrench, and as the piston came to the top, about 4oz gasoline gushed out. Cleaned holes out, blew each one out with compressed air for good measure. Gave each one a squirt of spray lube. Disabled injectors and ignition. Cranked engine. Sounds good. Put plugs back in. 2) Start engine. Starts. Runs good. Purrs like a kitten. Idles as smooth as can be. HOWEVER.... When I turn the key on without starting the engine, there is a clicking noise from behind the instrument console. There is a relay there, and it cycles intermittently, no pattern. When it cycles, I can hear the fuel pump run for a second. Injectors click. CEL flashes. So I disconnected the fuel injectors so I could work on it without the engine filling up with gas. Interesting enough, I was able to get the CEL to flash the codes for fuel injectors disconnected. So the computer functions enough for the engine to start and run, and it detects the disconnected fuel injectors. And still, that relay behind the dash cycles on and off. The questions are - what is it, and what controls it? It's possible the relay itself is defective, or whatever drives it is defective.

The SAGA continues :-) Received ECU from junkyard today. Installed. Turn key on, did not start engine. Nice and quiet like it should be (before it would trigger the injectors and the tack would jump, with key on and engine not running). Now it sits there quietly, tach does not jump, injectors do not cycle, cel is steady. This is very promising! Tried to start engine. WHAM. Engine jumps, horrible pounding noise comes out of engine. I only cranked it for a second, it did not start. I stopped cranking immediately when I heard the noise. omg wtf now what.... So, come to find out that the ECU failure caused the injectors to cycle when the engine was not running, and this poured gasoline into the cylinders. I drained the oil pan, and I drained almost 5 1/2 quarts of fluid from it (this engine takes only 4 quarts of oil). Very strong gasoline smell in the oil. It pumped so much gas into a non-running engine, that it caused the engine to hydrolock when I turned it over, and over a quart of gasoline drained into the oilpan. I have not had time to do this, but my plan this weekend is: Pull spark plugs. Turn the engine over by hand and make sure there is no gas in the cylinders. I'm thinking bring each cylinder to the top, and stick a rag into the spark plug hole to soak up any excess gasoline. Then disable ignition and fuel injection, and crank the engine a bit to clear out remaining gasoline from cylinders. Install plugs, put clean oil in engine, replace oil filter while I'm at it, try to start engine. I just hope it didn't bend a rod or otherwise damage the engine.