G3.Spiffy

Only got to drive the donor once but the symptoms weren’t present then, and it wasn’t driven conservatively. The previous owner had documents showing a complete engine rebuild, and had been driven for multiple thousand miles (don’t remember exactly) since then. They got in a crash and sold it to me. Had it trailered most of the way but I live off grid and drove it the last ~10 miles with no issues. It did awesome actually! Im pretty sure that whatever’s going on was somehow my doing.

The symptoms I reported in my original post were during driving conditions, but my more recent comment above was while sitting. Ive been planning to get a vacuum gauge set and fuel gauge set, but just haven’t gotten around to it. Looks like the time has come. I’ll try blocking the booster port and see if that symptom goes away. If it does it would mean a bad booster hose, hose connection to booster/manifold, or bad booster correct? I can’t really see any way the symptom would persist with it disconnected and the port blocked. Will you explain why having a clear bottle would help me diagnose? I’m open to it, just don’t understand it lol

Poked around in the FSM some more and narrowed down the dripping fuel a bit. The charcoal canister is connected to the fuel separator, which sends it gas fumes/vapor. If the separator isn’t working, could it be sending liquid fuel to the canister which is dripping out of the hose on the bottom? I also noticed that my EGR and purge solenoids get really hot... don’t know if they’re supposed to. Under what conditions does the purge solenoid vent the fumes into the intake manifold? If there is excessive fuel in the charcoal canister and the purge solenoid is allowing it into the manifold, could that be causing my drivability issues?

Just went and messed around with it a little. Started up great, no hesitation. When I pumped the gas a little and let off the idle dropped to about 700rpm as if it was warmed up, even though I had just started it, and slowly rose up to about 1500rpm where it stayed. If I revved it a little it would repeat that process until it warmed up a little, and it would only rise up to 1000, then finally to 700 and would rev normally. Once it was warmed up I got out and there was gas on the ground under my charcoal canister that wasn’t there before. It wasn’t dripping, so I set my camera up and got in the car and revved it a bit to see if that’s what triggers the fuel being dumped. No dripping at all... weird. Then I did the starter fluid trick and could find no evidence of a leak, but noticed that if I pump the brake the engine stutters a bit, which leads me to think it’s vacuum even more

After the first test drive I checked for codes as per the factory service manual (no codes reported), but will check again to make sure. I’m confident in my ignition system as the car runs great until driven, no misfires, proper idle, returns to idle after revved weather hot or cold. I’m confident in my timing as well for the same reasons. Since the issue only occurs when driving, how would I test if I’m getting enough fuel? I’ll check the location of the lines as well. Vacuum sounds promising though... I grabbed my EGR and purge solenoids (I think that’s what they’re called: the emissions ones shown in the sticker under the hood) from another spfi so it’s possible I grabbed a bad one. I’ll check for leaks as well. Much thanks!

In the process of swapping a SPFI ea82 engine into my 86 wagon I carelessly hooked up my fuel lines wrong and pumped fully pressurized gas into the evap line of my charcoal canister. This resulted in fuel pouring out the hose that comes out the bottom. I corrected my lines and went on to other things. Now I’m at the testing stage and have driven the car twice for a total of 14 miles. 12.7 for the first test drive. The first time I test drove it, the car did really well for a while. Then it started to bog down and loose power. It kept up like this until I got it home. I assumed this was due to the fact that the car was originally carbureted and doesn’t have fuel tank baffles, and that I didn’t have a full tank and was sucking up air. Filled up the tank most of the way and tried again a couple weeks later. This time the car acted very similarly, but didn’t make it as far before the same issues began. I got out and noticed that at idle the charcoal canister was dripping fuel. My dad was in the car with me, and has a bit more experience around older cars and said it seemed like the engine was flooding based on the drivability. What I know this could be: •Bad sensor input to ECU (CTS, MAF, O2, etc) •Blown FPR, which I doubt because it’s not a consistent issue, ie I have to drive a bit before it’ll start acting up •EGR valve stuck open or bad solenoid •Bad injector, which I also doubt because it’s not a consistent issue Since the car is preOBD it makes the diagnostic process more difficult (for me at least) and I’m having trouble pinpointing my issue. Any help to point me in the right direction or links to threads with similar discussions are appreciated!

On another note, took the car for a test drive just now. Went 11.8 miles (first real drive since the swap) with the only issue being what I can only presume is an intermittent fuel supply issue. I was driving down a hill of a decent grade and think I may have moved around my fuel (had a little less than a half tank) enough to pick up some air or debris with my fuel pump, either starving the engine of fuel or clogging up my filters or injector momentarily. The car bogged down quite a bit, then idled fine but the rpms would drop when throttle was given. Limped home and the issue got less noticeable and eventually went away just before I got back. Checked fluids just to make sure, and everything was good. Only code is a stored TPS code from the swap process that I haven’t cleared yet. The car was originally carbed, so it doesn’t have baffles in the tank and I haven’t installed a surge tank setup or dealt with that yet and I assume that might be the cause of my issue, but I’d like to know what others think of this as well.

This isn’t my issue because it doesn’t continue to stutter while the pedal is pressed, just when pumping it. That’s something I hadn’t thought of, just a slow reaction time... interesting. I’ve never noticed it in the other GLs I’ve encountered myself but sounds possible. A secondary leak sounds promising to me, but are you saying that’s only a possibility if I also have a bad booster? I may be misreading or misinterpreting what you said.

I’m finishing up the last few things on my EA82 SPFI swap (1986 GL 5MT) and am noticing a stutter at idle when the car is parked with the trans in Neutral and the brake pedal pressed and released. Initially I thought this was a vacuum leak, so I checked to make sure I have the booster hose on in the right direction, which it is, and that it holds vacuum, which I believe it does because I disconnected the hose after turning the engine off and it made a suction sound as if it was negatively pressurized. This only occurs when the brake pedal is pumped at idle, it’s not there if you rev the engine up a bit and then pump the pedal. The car runs fine otherwise. Any help or links to useful threads are appreciated!

Disregard this post!! The forum won’t let me delete it but I can edit so best I can do.

Much appreciated, good luck on your projects as well!

Exactly what I was thinking, but I’ve checked all power into the ECU from the ignition switch and it has power in where it should when it should according to the FSM diagrams. If it didn’t know it was running, the car wouldn’t actually run because it needs the ECU to control its functions right? I’m not sure how to go about tracking down what input could be missing aside form checking FSM diagrams, using a multimeter, and tracing wires. Which I feel I’ve done to the best of my ability. Any suggestions?

So, after finding out that all three of my ECUs are interchangeable, I put the one which I believed had the damaged transistor into the 92, and checked the function of things. Absolutely everything works... including the CEl... The good news is that my ECU is fine, but the bad news is I still have something going on which is preventing the CEL from functioning in the car I’m working on. After making this discovery I reinstalled the ECU in the car with the issue and got to work tracing things for what feels like the thousandth time. I absolutely, 100% have the two wires hooked up to the proper locations (one to 12v power and one to pin 2 of the ECU. I’ve swapped multiple bulbs which I know work with no change. The voltage gets all the way from the IG key position, through the bulb, and all the way to pin 2. Is the ECU not what grounds the CEL to check function before the engine is started? This is the only thing that really makes sense to me, but maybe someone else can help out.

Thank you, this saves me a lot of headaches. I didn’t know I needed to search them on a Subaru website. Hope this is able to help others as well!

I have three different spfi manual trans wagons, all are stage 2 (post wiring changes) and I need to know if the ECUs can be swapped around between them. Pictured are the ECUs in question. All have different numbering on the stickers. After some extensive searching I’ve been unable to find a thread which answers my questions. Links to threads which I may have missed are appreciated!

All of the cars are manual so theoretically I wouldn’t have to rewire anything, it would just be plug and play right? What are the chances that I could damage something if I throw the problematic ECU into the 92? This would allow me to test for function and interchangeability before installing a good ECU into a car that could still have something shorting out that circuit and see if it runs everything but the CEL in the 92. If the ECUs are the same, and I know for sure I’ve fixed whatever damaged the original ECU, I’ll probably just use the one with the good CEL just for my emissions test, then switch back because the 92 is all original and I’d like to keep all of its parts together until that’s no longer possible.

It seems highly likely this is what I did. Any advice on how to replace the transistor/IC chip? Or is the ECU no longer viable? If so, I have two other ECUs which are from a 90 and a 92 Loyale spfi manual trans. The systems that they run seem pretty close to identical but the sticker on the housings all have different numbers. Any info on spfi manual trans ECU interchangeably?

So if I understand what you’re saying (correct me if I’m wrong), it’s possibly normal for me to get the 5v reading mentioned earlier when the bulb is out (open circuit) depending on how the inside of the ecu is configured. If that’s the case can I visually observe this inside the ecu? Or would that be a part of an IC chip? Speaking in terms of the function of the CEL, the wire that exits the ECU and goes to the signal side of the CEL should be connected to ground whenever this transistor flips its switch, correct? If I understand what’s going on, there is something preventing the ECU from flipping that switch. This could be: •The switch is damaged and can’t function. •The ECU doesn’t know to turn on the CEL to test function with the key in IG and the engine off. This could be because of some other damaged internal ECU component or due to bad connections upstream. I’ve checked all connections outside of the ECU pretty extensively and am pretty confident my issue lies somewhere inside the ECU. What I need now is to diagnose what actually failed and figure out a course of action to fix it or replace the unit if necessary. I’m located in CA so I need the CEL to function to pass emissions unfortunately. Thank you for the input!

Yes, those were the other lights I was referring to. That makes a lot of sense, and is sort of what I got to as well. For whatever reason the ecu isn’t giving the signal to ground the connection. Based on this I uninstalled and opened up the ecu to inspect for burnt components or corrosion, which I found none of. The ecu is spotless inside. Is there any course of action from here? Can I track things farther somehow and make a repair if needed or do I have to pay some professional who probably doesn’t know what they’re doing to repair the ecu? I haven’t looked at the part number yet but I may have a spare ecu that I could swap in to see if that fixes things but if there’s some power issue still present in the car I’m concerned about damaging the second unit as well.

Could I have fried the IC chip related to the CEL?

I tested the other bulbs the same way, and all of them get the same reading on the IG side as they should, but two of them have ~2.5v on the other side and one has ~145mv. Those are the ones that work, so it’s weird that they don’t all read the same on the other side as well. That being said, the one that only has ~145mv is brighter than the other two working ones. Don’t know what to think of that

With a known good bulb in and it closed-circuit, there is still ~12v on the IG side but more like 10.5 on the other side. Is this normal? I’ll throw a different bulb in just in case, but did make the current one light up by opening the circuit and applying ground to the non 12v side of the circuit

After some extensive poking around I’ve determined that the only thing not working as it should is the CEL. The fuel pump “issue” was just test mode probing the fuel pump. The light on the ECU acts as it should in each test mode or read memory mode configuration, but I can’t get the CEL to come on for the life of me. If I take the bulb out and test the voltage on the circuit board, there is ~12v on the IG power side, and 5.something volts on the other side coming from the ECU. Same thing if I probe the proper pin at the ECU. I feel like this 5v signal from the ECU should function as a ground to turn on the CEL seeing as how it has power on the other side. Should my ECU be sending 5v out to the CEL? If not, what could cause this and what can I check to try and fix it? I’ve checked all my power going into the ECU and cleaned all the grounds which are associated.

Test connectors are unplugged Yea looks like you’re right. It seems like I have something funky going on electrically. I was poking around under the dash today double checking things and suddenly my fuel pump primed and was pushing fuel back into the tank. It only stopped when I jostled things around a bit so it looks like I have exposed metal making connections it shouldn’t somewhere... or maybe managed to damage my ecu somehow? The car still runs fine though so I doubt that. I’m leaning towards bad connection or I made an error when getting power to things. I had everything working just before this happened and have everything else working still, except the CEL, weird fuel pump issue, and light on the ecu.

So could it just be due to the engine being cold when I checked it while running? It wasn’t on long enough to heat up