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Hello again experts, the original thread on this at https://www.clublexus.com/forums/per...-on-sc300.html got really long so I'm starting a new one. Hope that's not an etiquette violation.
To summarize, my '95 SC300 started starving for fuel whenever I pushed past a certain, moderate amount of throttle. I put a new fuel filter in it and that wasn't the problem. I bypassed the FPECU directly and I thought that fixed it, but the problem returned. I finally took it to my local dealer and they said it was the corroded +B terminal at the alternator. They cleaned that up and I returned the FPECU connection to the original configuration. I've been driving it since then (March 10) with no problems. Been accelerating pretty hard occasionally, just to check whether it stalls again. No problems.
Saturday I was on the freeway going around 60-70 and decided to accelerate into the next lane and run it up to 80+ mph, to check the response. I hadn't had an opportunity to try full acceleration at highway speeds. As soon as I goosed the throttle the engine went dead. Not sputtering, not cutting in and out, stone cold dead. I managed to coast across 3 lanes to the shoulder without getting killed. Wouldn't start. Cranking strongly but not catching. I got the car home on a flatbed and fiddled around a little, then I tried the bypass from +B to Fp on the diagnostic port under the hood, as several people have done. (Before that I measured the voltage at the +B on the diagnostic port with the key out of the car, it read 0.3 mA.) The car started right up. I've driven it a little since and it's doing ok so far.
The last time I got home from somewhere and turned it off, I heard a steady hum behind the back seat. I was getting groceries out of the trunk and I could hear the sound, definitely coming from the gas tank area. I can't imagine anything in there that would be humming other than the pump. The key was in my pocket. I disconnected the jumper and it stopped. Today I reconnected the jumper and I don't hear it. Also something is mysteriously discharging the battery, sitting parked in the garage. So questions:
Is there anything in that space where the tank is, other than the fuel pump, that would be making noise? (It was not the CD changer, I know that noise.)
Is there any reason unrelated to the FPECU or the bypass I did, that could make the pump run with the key out of the car?
Is there somewhere else I can jumper the Fp to something, where it would only get voltage when the ignition is on? Without interfering with the other circuit?
What could be causing the battery drain? It's been doing fine for weeks, then it needed a jump after towing it home and parking it overnight. I charged it and drove it a little and then parked it for a couple of days and it's down to 7 volts right now. It's lost voltage before for no apparent reason too. And is there something that would be draining juice solely because the hood is open?
When the Fuel Pump cuts out, it is usually followed by Stuttering as the Fuel Pressure begins to Drop before the Engine cuts out, you either didn't feel the Signs of the Engine about to Stall (doubtful), or the Fuel wasn't originally the Problem that caused you to Stall on the Highway, but was rather a Secondary symptom of a different problem.
As written in your previous Thread, the Fuel Pump should not be On when the Key is out of the Ignition, the presence of the Jumper in the Diagnostics Connector should not cause it either, as the B+ Terminal in the Diagnostics Connector is connected to the EFI Relay, which is Controlled by the ECU, and must be Off when the Key is out of the Ignition, here is the specific post.
Again, check the EFI Relay, or better yet, Swap it with another one if you have it, if that won't help, get a Test Light and check if you have 12V coming to the Coil Side of the Relay when the Key is out of the Ignition, if that's the case, either the Engine ECU is shot and sends the Power to the Relay that should be Off, or you have an issue with the Wiring, here is a thread that explains the Switch and Coil Side of the Relay, it is very important not to confuse them.
Battery sitting at 7 Volts for more than a Day is no longer a Battery, rather a glorified Paperweight, I would no longer trust it, even if was New. The Hood being opened alone won't Drain the Battery, something else does that, and if the Theory about the EFI Relay staying On even though the Key is Out of the Ignition is correct, it would explain your Battery Drain too.
If you have more or less good access to the Fuel Pump ECU from the Interior, get a Test Light and Connect it to the B+ Terminal on the ECU, every time you take the Key out of the Ignition, look at the Test Light to see if stays On, which would indicate that the EFI Relay is still On, even though it shouldn't be.
Again, from how haphazardly this issue appears and disappears, I would try replacing the EFI Relay, or at least taking a look inside of it first.
P.S. And yeah, while it is okay to start a New thread for the same issue, make sure to put a link to this thread in the Previous one so that someone in the future can find this thread and is not stuck with no complete solution.
Thanks Arsenii, this is very helpful. You're obviously extremely knowledgeable and I appreciate you taking your time to help. If you ever have questions about blowout preventers, or heart valves, or Stirling cycle cryogenic cooler reliability, I'm here for you.
It sounds like that relay is a very likely culprit and that's a really cheap part, so I'm going to get one and try that. I'm a mechanical engineer and I have some understanding of electronics, but a lot of it is black magic to me. I do basically know what a relay does and if it's stuck or otherwise malfunctioning that would fit these symptoms.
I grew up on carburetors and points and all that stuff and I can diagnose and fix an old-school car pretty well. Troubleshooting a car that's so heavily dependent on electronics makes my head hurt. My entire suite of electronic test equipment consists of a Harbor Freight multimeter. and one of those screwdriver-shaped test lights with the sharp pointed end. I'd be dead in the water without this forum, or have this car in the shop all the time. So swapping out a cheap part is very attractive to me.
I do know the battery is damaged, it's been run down pretty dead several times. It still works well, except when it randomly gets discharged like this. For instance it was parked for over a week before Saturday, and it started just fine. It's Interstate and only a few months old, and they've always been good about warranty replacements. Getting another one shouldn't be a problem. I think I'll try a new relay first and see if that stops it from running the battery down, then go to the Interstate store and get them to test the battery. Thanks again.
Ok, here's an update. I bought a new relay and put it in, and the battery still discharges when the relay is plugged in. After leaving it overnight the battery was down to 7 volts again. I wondered if the battery is shot and discharging itself, so I charged it and disconnected the negative post. It held at 12.7-12.8 volts after 12 hours. I pulled the relay and reconnected the battery and it's holding voltage. It discharges with the relay in, but not with the relay pulled out.
The relay layout is different than the one you linked, which appears to be an ES. Here's the schematic printed on it:
I dug out my test light and found the only place there's voltage is the hole corresponding to pin 2, which I believe is correct. I checked the relay on my workbench, there's no continuity across 2-4 and 70 ohms across 1-3. No continuity across any other combination of pins. As best I can surmise, all this is as it should be and the relay should not be draining current without the key turned on. But it seems to be doing so. Relay plugged in, battery discharges. Relay pulled out, it doesn't. I'm stumped.
Meanwhile, with this new relay the pump situation appears to be the same. With the jumper from Fp to B+, the car starts and idles. I haven't tried driving it yet. Without the jumper it starts and runs a few seconds, then quits. This is with a fully charged battery.
Connect the Light Bulb straight to the Pins 1 and 3 on the Wiring Pigtail, see if it Lights Up immediately, or Only when the Ignition is in the ON Position.
If it is the former, the Light is On at all times, the ECU is likely confused about whether the Ignition is On for whatever reason.
If it is the latter, the Light Only turns On with the Key in the ON Position, do the following - with the EFI Relay in place, get a Test Light and connect it between Pins B+ and E1 in the Diagnostics Connector, check if it will turn On even with the Key out of the Ignition, if so, take the EFI Relay Out with the Test Light still in place, see if the Test Light will turn Off. This will indicate if it is, in fact, the EFI Relay that causes the B+ Terminal to keep staying On, or the issue is further Downstream.
Now that I think about it, you should also verify that the Wiring Diagram linked earlier is actually correct for your car. To do so, get a Multimeter with the Continuity Check, connect one Lead to Pin B+ in the Diagnostics Connector, and the other first to Pin 2 of the Relay, and then to Pin 4, see on which Pins you will get Continuity. This test is meant to see whether the EFI Relay even controls the B+ Terminal, since you mentioned that Pin 2 is the only one that is currently powered, it is the one connected to the Battery, then Pin 4 should be the Only Relay Pin that has Continuity with B+ Terminal. If it is the opposite, then in your case, B+ Terminal is not controlled with the EFI Relay, and the Diagram I've been referencing is Incorrect.
Since you mentioned that there is No Draw on the Battery when the EFI Relay is Out, you can verify it numerically by connecting the Multimeter set to Amp Meter in Series between the Battery and the Terminal, below is a video about it. Once you see the Amp Readings, pull the EFI Relay out and see if they Drop at all.
Hello, I did the checks yesterday. I'm inserting my results below, and adding some comments below.
Originally Posted by Arsenii
Connect the Light Bulb straight to the Pins 1 and 3 on the Wiring Pigtail, see if it Lights Up immediately, or Only when the Ignition is in the ON Position.
If it is the former, the Light is On at all times, the ECU is likely confused about whether the Ignition is On for whatever reason.
My test light is the kind that has a big clamp for the ground, to connect to the battery or a body ground. It won't probe small places. I used my multimeter at the fusebox across where pins 1 and 3 go and voltage was 0.0.
If it is the latter, the Light Only turns On with the Key in the ON Position, do the following - with the EFI Relay in place, get a Test Light and connect it between Pins B+ and E1 in the Diagnostics Connector, check if it will turn On even with the Key out of the Ignition, if so, take the EFI Relay Out with the Test Light still in place, see if the Test Light will turn Off. This will indicate if it is, in fact, the EFI Relay that causes the B+ Terminal to keep staying On, or the issue is further Downstream.
No voltage.
Now that I think about it, you should also verify that the Wiring Diagram linked earlier is actually correct for your car. To do so, get a Multimeter with the Continuity Check, connect one Lead to Pin B+ in the Diagnostics Connector, and the other first to Pin 2 of the Relay, and then to Pin 4, see on which Pins you will get Continuity. This test is meant to see whether the EFI Relay even controls the B+ Terminal, since you mentioned that Pin 2 is the only one that is currently powered, it is the one connected to the Battery, then Pin 4 should be the Only Relay Pin that has Continuity with B+ Terminal. If it is the opposite, then in your case, B+ Terminal is not controlled with the EFI Relay, and the Diagram I've been referencing is Incorrect.
Continuity only on 4.
Since you mentioned that there is No Draw on the Battery when the EFI Relay is Out, you can verify it numerically by connecting the Multimeter set to Amp Meter in Series between the Battery and the Terminal, below is a video about it. Once you see the Amp Readings, pull the EFI Relay out and see if they Drop at all.
Measured 0.16 mA with the relay in. Later I checked it again and got 0.02 mA.
Hope this helps and best of luck!
Other information: I drove it a little bit Saturday and had the same symptom as the original problem. Past a certain amount of throttle it lost all power. No sputter, no stutter, just quit like a switch turned off. As soon as I backed off the throttle it regained power. Did this a few times and the behavior was consistent. As long as I was easy on the throttle, it drove normally. I went home and parked it and 15 or 20 minutes later I decided to pull the relay, and it was extremely hot to the touch. Too hot to grab it and pull it, I'm pretty sure my fingers would have been burned. I got a thick rag and was able to pull it out. It was parked for a day or two with the relay removed, and the battery held voltage. After the fiddling yesterday I pulled it in the garage and left the relay in, and the battery is down again. The battery drain must have something to do with the relay, not some other stray circuit. That seems to disagree with the results of all these checks, but I don't know what else to think.
It seems like the engine ECU is a likely suspect. I see that there are rebuilt ones and repair services that are not too expensive, should I just do that? It's a cost I'm comfortable with to either fix it, or rule out the ECU as the source of the problem.
Also, I've been assuming the stalling is fuel-related, just from the way it feels when it happens. Is there something else that might do this? Ignition maybe? At times it has run perfectly normally for dozens of miles, then this problem comes back. When it does it's always the same, very consistent and predictable behavior.
One more thing that may or may not be related: The engine light is on sometimes and the last time it was checked it was an EGR code. Could that have anything to do with this? I'm told that bypassing that temp sensor with a 10K resistor clears that, but I haven't gotten around to that.
My test light is the kind that has a big clamp for the ground, to connect to the battery or a body ground. It won't probe small places. I used my multimeter at the fusebox across where pins 1 and 3 go and voltage was 0.0.
You can get the Terminals to fit in the Relay Pins at the Junkyard if you don't have any already. Whatever you do though, do not try Forcing anything Round like a Needle into any of the Terminals, you will end up Crushing the Spring Mechanism that makes those Terminals mate securely, destroying the Terminal.
You can use the Round tip of the Test Light as a Probe, just make sure not to Force it into the Terminal, you can only Touch the Terminal with it. It's a common occurrence to see people jam something into the terminal and then spend weeks chasing their tails with some flaky contacts.
Originally Posted by oldengineer
No voltage.
No voltage with the Key in the ON or OFF Position, or is it Both? It seems like the experiment was conducted incorrectly. If possible, get the Male Wiring off of an Old O2 Sensor at the Junkyard, it comes with Terminals that work perfectly with the Diagnostics Port, that way you can be sure of the proper Contact, and you will be able to use your bulky Test Light instead of a Multimeter.
Originally Posted by oldengineer
Continuity only on 4.
Perfect, the Diagram is correct.
Originally Posted by oldengineer
Measured 0.16 mA with the relay in. Later I checked it again and got 0.02 mA.
Was this Current measured with the EFI Relay in place or out of the car?
That Current is just about nothing. You should have at the very least a 50Ah Battery, which means that it will take a 50A Current to Discharge the battery in exactly an Hour, a Current of 0.00016A will take about 36 Years to run your Battery dry, somehow doesn't feel like it's been this long yet..
If the Relay was out of the car, put it back in and re-do the test. If the Relay was in place during the test, take your Battery to a Car Parts Store with a proper Carbon Pile Tester, they will test it for free to see if there are any signs of life still left in it.
Sorry, I don't know how to operate this well, quoting out portions of your comment to respond to. I'm putting my responses in italics. Maybe I'll learn later how to do a better job.
Originally Posted by Arsenii
You can get the Terminals to fit in the Relay Pins at the Junkyard if you don't have any already. Whatever you do though, do not try Forcing anything Round like a Needle into any of the Terminals, you will end up Crushing the Spring Mechanism that makes those Terminals mate securely, destroying the Terminal.
You can use the Round tip of the Test Light as a Probe, just make sure not to Force it into the Terminal, you can only Touch the Terminal with it. It's a common occurrence to see people jam something into the terminal and then spend weeks chasing their tails with some flaky contacts.
I'm using the tips on my multimeter and just touching the copper of the contacts in the diagnostic port, and in the fusebox where the relay goes. Not pushing them in. The only thing I've pushed into anything is the 20 gauge solid copper wire for the B+-to-Fp jumper on the diagnostic port.
If I'm reading voltage that's functionally the same as lighting a light, right? Just making sure I have that right.
No voltage with the Key in the ON or OFF Position, or is it Both? It seems like the experiment was conducted incorrectly. If possible, get the Male Wiring off of an Old O2 Sensor at the Junkyard, it comes with Terminals that work perfectly with the Diagnostics Port, that way you can be sure of the proper Contact, and you will be able to use your bulky Test Light instead of a Multimeter.
This was with the key off and in my pocket. No voltage between B+ and E1.
Perfect, the Diagram is correct.
Was this Current measured with the EFI Relay in place or out of the car?
That Current is just about nothing. You should have at the very least a 50Ah Battery, which means that it will take a 50A Current to Discharge the battery in exactly an Hour, a Current of 0.00016A will take about 36 Years to run your Battery dry, somehow doesn't feel like it's been this long yet..
If the Relay was out of the car, put it back in and re-do the test. If the Relay was in place during the test, take your Battery to a Car Parts Store with a proper Carbon Pile Tester, they will test it for free to see if there are any signs of life still left in it.
This was with the relay in and the key off. I know a fraction of a milliamp is negligible current, not enough for the battery to notice, so I don't get how it can be running the battery down.
The battery is functional enough for now, it holds charge if I pull the relay or disconnect the negative post. I can get a warranty replacement if it tests bad, which it probably will, but they might not like replacing it twice. If it's fully charged, above 12V with enough juice to start the car, then all these test results are valid, right?
So I'm still having what I'm interpreting as a fuel supply issue and pretty much assuming it's the FP ECU. Could it be a fuel pressure regulator or something I'm not thinking of, or the main ECU sending the wrong signal to the FP ECU?
I'm probably going to send the main ECU to a shop, unless you disagree, or buy a rebuilt one. Do you recommend anyone in particular for that? I see a couple of shops online, and reasonably priced rebuilt ones too. If more than one business is sustaining themselves fixing them, then issues in that box must be pretty common. I feel like I might as well get that checked out/refurbished regardless. It's worth the relatively small cost to me. If that solves one or both of my problems it will be well worth it.
Hope this helps and best of luck! Thanks again.
Other information: I drove it a little bit Saturday and had the same symptom as the original problem. Past a certain amount of throttle it lost all power. No sputter, no stutter, just quit like a switch turned off. As soon as I backed off the throttle it regained power. Did this a few times and the behavior was consistent. As long as I was easy on the throttle, it drove normally. I went home and parked it and 15 or 20 minutes later I decided to pull the relay, and it was extremely hot to the touch. Too hot to grab it and pull it, I'm pretty sure my fingers would have been burned. I got a thick rag and was able to pull it out. It was parked for a day or two with the relay removed, and the battery held voltage. After the fiddling yesterday I pulled it in the garage and left the relay in, and the battery is down again. The battery drain must have something to do with the relay, not some other stray circuit. That seems to disagree with the results of all these checks, but I don't know what else to think.
It seems like the engine ECU is a likely suspect. I see that there are rebuilt ones and repair services that are not too expensive, should I just do that? It's a cost I'm comfortable with to either fix it, or rule out the ECU as the source of the problem.
Also, I've been assuming the stalling is fuel-related, just from the way it feels when it happens. Is there something else that might do this? Ignition maybe? At times it has run perfectly normally for dozens of miles, then this problem comes back. When it does it's always the same, very consistent and predictable behavior.
One more thing that may or may not be related: The engine light is on sometimes and the last time it was checked it was an EGR code. Could that have anything to do with this? I'm told that bypassing that temp sensor with a 10K resistor clears that, but I haven't gotten around to that.
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Originally Posted by oldengineer
If I'm reading voltage that's functionally the same as lighting a light, right? Just making sure I have that right.
Not exactly, I try to avoid using a Multimeter where possible, the difference is that the Light Bulb puts an actual Load on the Circuit, making it a lot more Reliable in cases of a Damaged Wire for example, where the Voltage will be present, but the wire can't sustain said Voltage under Load, as well as in cases of Bad Ground or a Disconnected Wire, where Voltage in One wire can Couple itself onto the Other wire, even though it won't be able to power anything, you will still see the Readings on a Multimeter, a Test Light with its ability to put Load on the system makes easy work of clearing that confusion.
Originally Posted by oldengineer
This was with the key off and in my pocket. No voltage between B+ and E1.
Was the EFI Relay installed back into the car?
Well that throws a wrench into the idea that the EFI Relay stays Active, unless you have an Intermittent issue, which can be one wild goose chase to trace. One thing you can do is put a Light Bulb between B+ and E1 Terminals, or maybe even a Horn from the Junkyard, something that is sure to get your attention, and leave it there overnight, if you see the blinding light or hear a bellow of a wild animal coming from your garage even though the key is still in your pocket, you will know for sure that there is a problem to be solved.
Just make sure to not attempt to drive off with that newly acquired burglar alarm..
Originally Posted by oldengineer
If it's fully charged, above 12V with enough juice to start the car, then all these test results are valid, right?
What I was really trying to make sure of is that the Battery just isn't dead as a doornail just yet and can still hold 12V overnight, provided that nothing in the car drawing power would run it flat. Sounds like it can still hold it together for now, so there is no point in replacing it just yet.
Originally Posted by oldengineer
So I'm still having what I'm interpreting as a fuel supply issue and pretty much assuming it's the FP ECU. Could it be a fuel pressure regulator or something I'm not thinking of, or the main ECU sending the wrong signal to the FP ECU?
Currently I am more concerned by the fact that you can have some system turn on at Random, completely unprompted, and the only item that can do it is your Main ECU it appears, seeing that taking the EFI Relay out for the night does get rid of this behavior. With all the tests described earlier, the task is to Isolate the ECU as the only component left that can result in the EFI Relay coming on at random even with the Key out of the Ignition.
Originally Posted by oldengineer
I'm probably going to send the main ECU to a shop, unless you disagree, or buy a rebuilt one.
You can send the Main ECU for a check, but you have to understand that a quality repair is really not as cheap as you may think, so it would be helpful to do all you can to rule out any other problem that can be causing this behavior before committing to it, only for the Repair Shop to declare that the ECU is good working order, but if that's the route you want to go with, you are more than welcome.
While I myself am yet to use any of their services, Tanin Auto seems to have a solid reputation around here, they also have, or at least had at some point, a fleet of their own cars they use to be absolutely sure that the ECU performs as expected, so it would likely be a route to go.
Not exactly, I try to avoid using a Multimeter where possible, the difference is that the Light Bulb puts an actual Load on the Circuit, making it a lot more Reliable in cases of a Damaged Wire for example, where the Voltage will be present, but the wire can't sustain said Voltage under Load, as well as in cases of Bad Ground or a Disconnected Wire, where Voltage in One wire can Couple itself onto the Other wire, even though it won't be able to power anything, you will still see the Readings on a Multimeter, a Test Light with its ability to put Load on the system makes easy work of clearing that confusion.
Ok, that makes sense. I don't know if that matters in these cases, but I get what you're saying.
One thing you can do is put a Light Bulb between B+ and E1 Terminals, or maybe even a Horn from the Junkyard, something that is sure to get your attention, and leave it there overnight,
I think I can do that. I have some spare 12V bulbs, and I have security cameras. I think I can set a camera in the garage and get it to alert me on my phone if the light turns on. But is that going to tell me anything new?
With all the tests described earlier, the task is to Isolate the ECU
Totally agree, but if the ECU is the only thing that can be doing this, haven't we basically done that?
I'm already looking at Tanin, they do have test cars. A 300 and a 400. But they might have trouble testing for a sneaky intermittent issue like this. I'll contact them and outline my symptoms, maybe they'll be familiar with this condition. There are rebuilt ones, but I don't know how well tested they are. I'll see about setting up something to detect the B+ to E1 thing, and look further into ECU repair/replacement options. Thanks, and thanks for the info about quoting.
I don't know if that matters in these cases, but I get what you're saying.
It probably doesn't in this case, but helps to eliminate all possible variables.
Originally Posted by oldengineer
But is that going to tell me anything new?
It seems like the EFI Relay has been causing a draining battery for a while now, but every time we tried to catch it red-handed, we came up empty-handed, the Relay works, the Coil Side Signals all seem good, there is no Voltage between B+ and E1 Terminals every time you go to check it, and yet, taking an EFI Relay out, the Relay that stayed Off every time you checked it so far, somehow eliminates the Draw on the Battery. The point of this test is to see whether the EFI Relay somehow gets Triggered over time, or something else is causing the Draw, and the EFI Relay is just there as a by-stander.
Originally Posted by oldengineer
Totally agree, but if the ECU is the only thing that can be doing this, haven't we basically done that?
Just about there I would say, if you will see the EFI Relay get tripped with the car just sitting in the Garage, that will be pretty much the definitive death sentence for the ECU, as again, it's the only system as far as I can tell that has an ability to Trigger the EFI Relay, at least without the Key in the Ignition.
Ok, I rigged up a light and a buzzer and the contraption lights and beeps when I cross the battery with it. It has solid 20 gauge wire ends that plug nicely into the diagnostic port. Positive to B+ and negative to E1. I expected it would light when I turn the key on, but it doesn't. Should it? Also, does it matter whether the relay is plugged in for this test?
Last edited by oldengineer; Apr 15, 2025 at 04:48 PM.
I expected it would light when I turn the key on, but it doesn't. Should it?
Wait what..? Yes, turning the Ignition to the ON Position is supposed to send the Power to the B+ Pin, it *should* have tripped the contraption you rigged. EFI Relay should be On every time the Key is in the ON Position, and the B+ Terminal in the Diagnostics Connector is powered directly from the EFI Relay, if the Relay is On, you will have power on B+ Terminal. It seems like, for whatever reason, the EFI Relay did not turn On when you turned the Key to the ON Position.
Was the EFI Relay in place during that test? If not, it has to be in place for this test to work, as again, that is what directly powers the B+ Terminal.
With the Key in the ON Position and the Relay in place, try connecting one end of your Buzzer System to the B+ Terminal, and the other Directly to the Negative Battery Terminal, then, connect one end of the Buzzer to the E1 Terminal, and the other to the Positive Battery Terminal, the Buzzer should sound with Both tests. The aim of this test is to ensure that there is no damage in the Diagnostics Connector, that the B+ Terminal does have Power on it, and that E1 Terminal does have Chassis Ground on it.
Well, that's another twist isn't it? I'm fairly sure I did everything right, but I'll do these checks and see where that leads.
I think I'm going to take the engine ECU out and look inside. Apparently some capacitors in there are prone to leaking with age, and etching through pathways on the board. If it's visibly damaged it will obviously need to be repaired or replaced, regardless of anything else. Might as well do that, then see how the car behaves. Thanks again.
Update: There's no voltage at B+ with the relay installed and the key turned on. I checked that there is power to pin 1 of the relay and verified function of the relay. I tried it with the new relay and the old one. Car does not start at all now, with or without the Fp-B+ jumper. I confirmed the E1 is grounded. I have the ECU out now, looking into repair or replacement options.
Last edited by oldengineer; Apr 16, 2025 at 10:00 AM.
I checked that there is power to pin 1 of the relay and verified function of the relay.
This, in fact, means that the ECU is Working and it does attempt to Trigger the Relay. Try checking the 30A EFI Fuse, that's what powers the Switch side of the Relay, is appears to be what you are missing, though why it would blow like that is another question entirely.
Taking a look inside of the ECU is still worth doing though, just in case, it is a known issue with those cars after all.
still fighting that fuel pump ECU
