Fried ECU

[davepak]

New development:

Well it turns out that my dad's Digital Multi Meter is off. It needs calibration and I didnt realize sbout it, only by chance today when I took a cheap one and by chance compared them.. The cheap one reads 12.36 volts on the battery and the other one 11 point something. Now THIS IS significant because I can infer now that the pump receives its needed 12 volts and most likely the car can operate both radiator fans. Ill go down now and work on this. Additionally, the voltage in the car should be working fine.

 

[davepak]

1 hour ago, idosubaru said:

EA81 wagons are nifty.  After that I’m done with wagons except newer ones.

They are indeed. Ive always like them all. But generally, I like coupes, or sport hatchbacks.. so the XT was the best of all among those for me..

[DaveT]

PWM of the fuel pump is highly unlikely.   These cars are way simpler than that.   My EA82s non turbo, the alternator output is low enough at idle to let the battery voltage drop to where it barely keeps up with running the engine.  Especially with other things, like a fan or the ac on.     The voltage goes up to charging level when you get above idle.  The fuel pump obviously drifts up and down with the fluctuations.  The wires to the pump are likely  shielded to keep the noise generated by the commutator and brushes from getting into the AM radio,  etc.

[idosubaru]

2 hours ago, DaveT said:

PWM of the fuel pump is highly unlikely.   These cars are way simpler than that.   My EA82s non turbo, the alternator output is low enough at idle to let the battery voltage drop to where it barely keeps up with running the engine.  Especially with other things, like a fan or the ac on.     The voltage goes up to charging level when you get above idle.  The fuel pump obviously drifts up and down with the fluctuations.  The wires to the pump are likely  shielded to keep the noise generated by the commutator and brushes from getting into the AM radio,  etc.

that's what I was thinking but I don't know for sure or have anything to back it up.  

[davepak]

4 hours ago, DaveT said:

PWM of the fuel pump is highly unlikely.   These cars are way simpler than that.   My EA82s non turbo, the alternator output is low enough at idle to let the battery voltage drop to where it barely keeps up with running the engine.  Especially with other things, like a fan or the ac on.     The voltage goes up to charging level when you get above idle.  The fuel pump obviously drifts up and down with the fluctuations.  The wires to the pump are likely  shielded to keep the noise generated by the commutator and brushes from getting into the AM radio,  etc.

I agree with you @DaveT it looks like this shielded wire's purpose is only as a tiny faraday cage/mesh in case of noise affecting the signal coming from the ECU. I have put everything back together as factory specs. The shielded wire does not touch the negative lead of the fuel pump, it stops maybe 10 cm before that lead.

Edited January 29, 2021 by davepak
content added

[davepak]

1 hour ago, idosubaru said:

that's what I was thinking but I don't know for sure or have anything to back it up.  

Has to be a tiny subsystem to protect against noise, but not to be connected to the negative lead of the pump

[davepak]

As discovered earlier, the DMM is off by more than a volt, giving me wrong readings. So the fuel pump receives the appropriate voltage, (see the pic) which goes up and down as per rpms and battery load..But it is in fact appropriate voltage, the shielded wire's function (the other pic) must be to act as a sheath that suppresses any noise along the wire loom from the ECU to very near the pump as pointed out by DaveT. (now those wires are properly insulated and protected.

 

Here goes the next line of thought:

Fuel tank issues? 

Remembering the car's behaviour since day one (my day one) it always had that sputtering, I remember replacing the fuel filter for the first time, to discover a lot of debris there. However, the car worked and it has had at least 2 more fuel filters in less than 500 miles of actual running.

But yesterday, the car just stalled and died on my driveway, which has an inclination of at least 30 degrees. In the past and even recently anytyme the car is in a nose up attitude it will struggle, sputter and loose performance and driveability.It barely climbs and it is faster to over take it seated on a turtle. The other thing I managed to see was that there was no pressure measured at the regulator, a flat zero, I jumped the test connectors to cycle the fuel pump, it'll work but it would not build pressure. I backed the car up and once it leveled, I fired it and it started like business as usual. On my test drive on a flat road, the car would speed up great, but when I started to go uphill... barely going

So then, the question is: Are there any issues affecting the fuel delivery from the tank somehow? 

What can I test or do as part of a troubleshooting?

 

Edited January 29, 2021 by davepak
content added

[idosubaru]

Excellent!   That nose up/nose down sounds telling if it's repeatable and happens the same way every time like you said.  Not sure what it means, but good info. 

23 minutes ago, davepak said:

I remember replacing the fuel filter for the first time, to discover a lot of debris there.

Describe debris?  I've changed a ton of old Subaru fuel filters and they'll always spill out perfectly clean gas with no signs of debris or dirt at all, not to even mention a clog.  I've seen so many like this over 25 years I question the efficacy of replacing them and have significantly cut back how often I do so.   I'm interested in what you saw. 

What about the fuel sock on the original fuel pump you pulled - on the intake is a small plastic screen cap, did that have anything on it?  I've equally never seen them have anything on them either.  

[el_freddo]

I know where to go from here. Boat anchor the EA82, do an EJ22 conversion. Win win. 

Cheers 

Bennie

[1 Lucky Texan]

if you can find the right height goind up on a pair of ramps, or up on a stack of wood, etc., At which the car will run but 'stumble', try spraying starter fluid in the intake. If it smooths-out, you just proved it has some kind of fueling issue.

[DaveT]

Yeah, that angle and stuff effecting the engine running sounds really suspicious.   How does the pump get the fuel out of the tank on this version?   Could the pickup tune have a crack or other failure  that let's it suck air at certain angles  / under heavy acceleration? 

 

Re the sheild - normal sheild practice is that only one end is grounded.   You don't want current flowing in the sheild,  it is only supposed to absorb the unwanted signal.

[davepak]

34 minutes ago, DaveT said:

Yeah, that angle and stuff effecting the engine running sounds really suspicious.   How does the pump get the fuel out of the tank on this version?   Could the pickup tune have a crack or other failure  that let's it suck air at certain angles  / under heavy acceleration? 

 

Re the sheild - normal sheild practice is that only one end is grounded.   You don't want current flowing in the sheild,  it is only supposed to absorb the unwanted signal.

Awesome inputs! This fuel pump has a pipe that enters the tank at the lowest point in the front of the tank and goes up to the top of the tank, then goes down to a "suction structure" as I'm calling it. Ill work on opening the tank and clean that real good.

As per the shielded wire, thank heavens I read your comment about it, I left it as per factory, where only one side is grounded (via the ECU) 

[davepak]

New development: 

As a PITA as it is, I removed the fuel tank together with the rear differential assembly.

Upon inspection (and plenty of suspicion) I found a lot of debris inside the tank, I also found the tell tale signs of work on the tank before. Someone had already cut the tank to address -most most probably- the same issue. Clogging of the inner filter/siphon assembly. And I mean a lot of debris. Curiously this suction structure is located at the very back of the fuel tank, which in an inclined position will concentrate the last amount of fuel if the tank has little fuel, but also all kinds of grime and debris if they were present. And boy they were.

In retrospect.. This car had rode very little, my suspicion is a faulty TURBO and subsequent problems thereafter. As such, the tank had little fuel and the rest evaporated, leaving possibly water and a lot of air, perfect recipe for heavy corrosion. Once the tank was filled again (maybe months after) you have a tank with a lot of debris. To describe it, it looks like ground coffee!

So the course of action is the inevitable: I'll wash this tank like there is no tomorrow, I'll fill it with soap and water, and when safe, I'll cut an opening to access that suction stucture and remove all residue, grime, rust and long forgotten thoughts that may still be trapped in there.

In the mean time, I'm also addressing a collision dent on the rear quarter panel that was accessible when I removed the back seats and trim panels to address the fuel pump issues. Body filler and fresh paint coming soon.

Cannot say I have nailed it, but it sure feels like it. Yesterday the car just stalled and died on my inclined driveway, and it only worked when I levelled it horizontally. Enough of a hint?

Back when it worked a bit, it would drive nicely on flat road, but as soon as a steep hill would come up, it'll stall badly halfway and it would not work, I'd wait (like for a miracle ) and it would carry on badly, sputtering and coughing. The clues all point at clogging and heavily reduced fuel availability, despite the fuel pump's attempts to meet the requirements. It would simply suck in more but then get clogged more at the same time. Once again, the suction structure is at the back of the tank, where all the rust and debris collects. Darn!

 

Is that welding joints in there??

 

 This is some debris inside!

And the amount I collected on the pan!

I

Edited February 2, 2021 by davepak
Content added

[davepak]

4 hours ago, 1 Lucky Texan said:

if you can find the right height goind up on a pair of ramps, or up on a stack of wood, etc., At which the car will run but 'stumble', try spraying starter fluid in the intake. If it smooths-out, you just proved it has some kind of fueling issue.

When seeing the amount of debris and dirt inside of this tank, I can see why the fuel pump would struggle. Imagine the Gold Rush era, I was holding a pan with so much dirt (looked like ground coffee) that I only wished it was gold! 

[davepak]

On 29/01/2021 at 3:58 PM, el_freddo said:

I know where to go from here. Boat anchor the EA82, do an EJ22 conversion. Win win. 

Cheers 

Bennie

Ha haha, I really dont want to do any more heavy work on this car, I just want to go do the darn groceries with it, or the odd ride anywhere 

Edited January 31, 2021 by davepak
Grammar check

[idosubaru]

26 minutes ago, DaveT said:

   How does the pump get the fuel out of the tank on this version? 

It’s an EA82 fuel pump.

So what you’re asking is probably configured exactly like an EA82 with minor XT specific geometric differences.

[davepak]

On 29/01/2021 at 2:54 PM, idosubaru said:

Excellent!   That nose up/nose down sounds telling if it's repeatable and happens the same way every time like you said.  Not sure what it means, but good info. 

Describe debris?  I've changed a ton of old Subaru fuel filters and they'll always spill out perfectly clean gas with no signs of debris or dirt at all, not to even mention a clog.  I've seen so many like this over 25 years I question the efficacy of replacing them and have significantly cut back how often I do so.   I'm interested in what you saw. 

What about the fuel sock on the original fuel pump you pulled - on the intake is a small plastic screen cap, did that have anything on it?  I've equally never seen them have anything on them either.  

Debris just like ground coffee, like wet sand, when agitating the tank it sounded like sand inside a giant pan! These are chunks of rust!

Edited January 31, 2021 by davepak
Grammar check

[idosubaru]

6 minutes ago, davepak said:

bris. To describe it, it looks like ground coffee!

In the mean time, I'm also addressing a collision dent on the rear quarter panel 

Awesome!!!! You definitely found the issue. Well done. You deserve a cookie!  that’s a brutal job to pull the tank - how was it?

Do you think the accident that caused the rear quarter damage caused the tank damage?

Do you think the original burnt ECU is related or just an artifact of sitting, someone previously working on it?

So You found wiring tampered with, body work, and a burnt ECU...

 

[davepak]

25 minutes ago, idosubaru said:

Awesome!!!! You definitely found the issue. Well done. You deserve a cookie!  that’s a brutal job to pull the tank - how was it?

Do you think the accident that caused the rear quarter damage caused the tank damage?

Do you think the original burnt ECU is related or just an artifact of sitting, someone previously working on it?

So You found wiring tampered with, body work, and a burnt ECU...

 

Oh dear this IS some investigative work!

I confess I love forensic files. There is always some clue somewhere, and many times the most likely suspect is the actual killer

So, I think the issue with the tank comes from the malfunctioning TURBO, it was toasted (back in 2015 or 2014 when I got the car) because of that and the UBER complicated amount of systems of this type of car, any Car technician working on it would never figure out.. anything in fact. All peripheral sensors were broken (coolant thermosensor, knock sensor, thermo switch, O2) 

As per the ECU being burnt, my thoughts are with a short circuit, and most probably the harnesses of the injectors. One of them smoked badly at one point and in the end I remade all 4 injector harnesses (and a second burnt computer)

That wire of the pump (the shielded wire) was tampered with, here my dad gave me his 2 cents on that, because he knew about PWM, signals, noise suppression and more from his telecom times. The person who tampered there did not know about this and thought a ground point was needed for the fuel pump. But instead, it was a clean, unclogged fuel line what was needed. However, in splicing the negative wire and attaching a lead to the chassis, this would "send loose" the signal to chassis rather than the pulse control as ground coming from the ECU. (A potential additional problem to the ECU)

The body work, yes, this car was in a colilsion, front end and sides, mainly the LHS rear panel. ..

What a true investigative work. And Im not done.  

Below is a crude representation of what is inside the fuel tank. That blue pipe ends in what I call the suction structure, right at the back of the tank, where all the debris collects especially if the car is in a nose-up attitude. This will be examined thoroughly tomorrow after washing well the tank and cutting an opening safely. 

Edited January 30, 2021 by davepak
content added

[davepak]

Oh and @idosubaru removing the fuel tank was not a task for the faint hearted. But not that bad actually, at the end I asked my dad for help in guiding it out. I needed to remove the rear differential assembly (like a crossmember bar that holds the rear differential) quite a bunch of hoses and it was out.

Edited January 30, 2021 by davepak

[Rampage]

Good job.

That stuff on the outside of the tank, could it be epoxy? JB Weld, Permatex and others make an epoxy for fuel tanks. I have used the one that comes with fiberglass matting.

I changed the fuel tank on our RHD 95 Legacy wagon. It is not a fun job. I was able to use a lift at a friends garage. I used small ratchet straps one on each side of the diff to hold it while removing the tank.

Does this look like your tank? 1986 Subaru XT Fuel Tanks & Components at CARiD.com

Don't know if you want to spend that much money on one. It is bare metal and needs primer and paint. I put bed liner on mine to handle the stones on back roads.

[davepak]

19 hours ago, Rampage said:

Good job.

That stuff on the outside of the tank, could it be epoxy? JB Weld, Permatex and others make an epoxy for fuel tanks. I have used the one that comes with fiberglass matting.

I changed the fuel tank on our RHD 95 Legacy wagon. It is not a fun job. I was able to use a lift at a friends garage. I used small ratchet straps one on each side of the diff to hold it while removing the tank.

Does this look like your tank? 1986 Subaru XT Fuel Tanks & Components at CARiD.com

Don't know if you want to spend that much money on one. It is bare metal and needs primer and paint. I put bed liner on mine to handle the stones on back roads.

I'm not so sure if it is some epoxy.. But I'm planning to add a layer of a "siliconizer" product I have for the underbelly. 

And.. Yes that's a spot on tank for the XT. Won't be able to spend on a new one, but with this one is ok, I can make it almost as good as new. 

What's the bed liner product you used? 

And removing the tank wasn't that bad, but fiddly indeed. I used a jack to hold it in place then my dad lowered it while I held it. Eventually it came out. There wasn't much fuel in it so it wasn't that hard to handle

Edited January 31, 2021 by davepak
Grammar check

[1 Lucky Texan]

good time to inspect any brake lines that might run above the tank.

[Rampage]

2 hours ago, davepak said:

What's the bed liner product you used? 

Rhino Linings spray on bed liner. The body shops around here told me it was a good product. Price and results.

My wife used to deliver mail and the car door was collecting a lot of scratches from the mailbox doors dropping against it, so I sprayed some on the drivers door from the chrome down to the handle. It really works.

[el_freddo]

Isn’t an XT tank the same as an L series EFI tank? I always thought the Vortex/XT4 were all based on the L series chassis/floor pan design with the changes being the body construction and styling. 

I don’t know the availability of the L series/Leone’s over your way @davepak. 

And certainly in this case, an EJ conversion would not solve this issue as it would do the same thing! 

Very lucky you didn’t burn through all the fuel pumps you tried out. 

Now, what about putting that turbo back on? Go on, you know you want to for that extra reliability factor!   

Cheers 

Bennie