posted by
someone claiming to be cdcrawford
on
Wed Oct 25 22:34 CST 2017 [ RELATED]
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An update to this post:
https://www.brickboard.com/RWD/volvo/1649240/220/240/260/280/new_brick_slow.html
I ended up swapping out the ECU with a "known good" one and, lo and behold, the car runs properly now. Down to a scintillating 12.4 seconds 0 - 60.
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Hi, thanks for the follow up!
I have a 1984 sedan.
How slow was the car before?
Can you tell us what ECU number your car had and which one does it have now?
We need to record those that go bad early or just from age.
We all know Even the color of the labels makes a difference in later years.
You said it was a know GOOD working one. How did you determine the difference first?
Are you just lucky at the PNP or bought a rebuilt? If so what brand?
Is this on it a non- California smog car?
I'm learning right now that there are separate strut labels.
Phil
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posted by
someone claiming to be cdcrawford
on
Tue Oct 31 12:37 CST 2017 [ RELATED]
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Machine Man,
Sorry for the delayed response. I haven't been on the BB for a few days.
Both the (I assume) original ECU and the salvage yard replacement had a small, red label on them with a part number ending in -503. There were no other identifying markings on the ECU.
This car, when I got it, was not running. I brought it back to life with a new fuel pump relay and a timing belt. I also went through and redid the brakes and a few other things. The body and interior are in amazing shape for the age of the car - if you did not know better, you might think that it is about 10 years old instead of 34 years old. Also, it was "gifted" to me for the cost of the DMV fees, so I did not feel bad about putting a few bucks into it.
Anyway, I got it running, but it was god awful slow. About 17 1/2 seconds 0-60. And this is a manual (M46) car. A healthy B23F should be able to do 0-60 in around 11 or 12 seconds with a stick. Otherwise, it ran well. Normal gas mileage (low 20s in town, 25-26 on the road) and no other symptoms. I swapped out a bunch of crap trying to get it to run as it should, but no joy.
I swapped the ECU as a last resort and that seemed to do the trick. The salvage yard about 10 miles down the highway from me had a couple 503's on the shelf, already pulled and tested, with a 90 day warranty, for $50 each.
I opened the old ECU and there are several "bloated" capacitors, as well as a few that appear to be leaking. I'd like to repair this one if I can, but I am not sure where to start.
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Just to add some info - my 1983 (build date Oct 1982) had the -503 ECU, but I read somewhere that 1984 models and perhaps late 1983 production (both still with the LH-II system) changed to a -510 ECU.
So when I found a 1984 240 in the JY, I pulled the -510 and swapped it into my '83 on the basis that newer is better. As far as I can tell, no difference whatsoever. Fuel economy, starting, driveability etc. all the same. So I would guess my -503 was fine.
I believe that the late '83 and '84 cars employed a heated O2 sensor, and perhaps that is the only change to the ECU... to trigger the heater on cold starts and warmup. The -510 works fine with no heated O2 sensor in my early production '83, and the -503 is in the trunk with the other roadside repair parts.
--
Bob: Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), 98 S90 (recently sold) and XC60. Also '77 MGB and four old motorcycles
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We've also owned both 83 and 84 non-turbo (LH2.0 B23F) bricks, both with automatics. The June production 84 had the 510 but no wiring for a heated O2 sensor in its original harness. I'm sure the 510 in our 84 was the original, and I've never seen anything else in an 84 when I cruised the junkyards back then. I could also use the 510 in our 83 without any advantage perceived over the 503s. We had two 503s, and I did some extensive electrical comparisons.
My conclusions about the heated oxygen sensor were supposedly a late 84 (84.9) change did not need any support from the ECU. The heater was switched by the key switch, not any logic involved, and because the -510 ECU predated the harness with the heater, I conclude there was no firmware fuel trim change to take advantage of the quicker warmup, just the benefit of closed loop AFR control occurring earlier in the warmup.
There could be many reasons a particular ECU would result in a slow car, and I think every one of them would be apparent by monitoring the oxygen sensor; the ECU's only critical job being that of assigning the correct amount of fuel to the amount of air being measured. As regards the differences between the -503 and the -510, I have to believe, if it weren't manufacturing efficiencies driving Bosch to a new part number, it was emissions targets.
--
Art Benstein near Baltimore
"Never trust the work of the last guy, even if you're the last guy"
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posted by
someone claiming to be cdcrawford
on
Tue Oct 31 20:44 CST 2017 [ RELATED]
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Art,
That was what my gut told me.....an issue with the circuit that controlled the oxygen sensor or AMM. I know that I swapped both (o2 and AMM) with no effect.
I still have the old ECU. I'd rebuild it if I knew how. Any ideas?
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Hi cdcrawford,
Disclaimer:
I'm NO expert in ECU repair but I have refurbished my LH2.4 ECU (Bosch #0280000935) in the past. I have no LH2.0 ECU to examine with but what I could gather from photos on the net is that the LH2.0 board is more densely populated with electronic components than the LH2.4 board (this means you really need good lighting for checking plus fine tip soldering iron to attempt repair).
General tips are:
1. The ECU board is double-sided (the traces are on both sides) so you'd need to dismantle the board out of its aluminium backplate to fully examine it. Careful not to flex the board too much when dealing with the plastic pegs holding the board to the backplate.
2. Your ECU is still working (albeit slow acceleration response) so I don't think you'll find any burnt components on it.
3. Replace any BLOATED/LEAKING electrolytic capacitors on the board with new ones of the same value. Replacement capacitor could be ordered from MOUSER/DIGIKEY electronic part supply. I use Farnell (Element 14) and RS-Malaysia as they offer free posting in my country. If any capacitor is leaking, clean its surrounding areas with isopropyl alcohol (on cotton buds) prior to putting a new one. LEAVE the film capacitors alone as they are mostly long-life.
4. Check for any cracking at ALL solder points/joints across the board (the other side too). Re-solder them again. ONLY re-solder those affected. LEAVE the intact ones (non-cracking) alone. THIS IS IMPORTANT --> Because this is a double-sided board check BOTH sides of the same solder joint. You might need to solder the same joint twice (one side and its opposite side) especially for the big joints if your iron is not hot enough to reach both sides. The electrolytic capacitors usually connect BOTH sides of the board so check the solder on both sides.
5. Pay special attention to empty soldering points too (those without any components). These may be VIA (vertical interconnect access) or PTH (plated thru holes). They connect BOTH sides of the board (check both sides to confirm). Re-solder them if any cracking is seen. Also check both sides after soldering.
6. Don't dwell too long on any soldering point. No more than a few seconds (5 seconds max) to avoid overheating of components and destroying the PCB track (the track may detach itself from board). If first attempt unsuccessful, let the component cool down for a while and try again.
7. I'm not sure if the LH2.0 board uses any LDO (low dropout voltage regulator). The LH2.4 board uses them. These voltage regulators are transistor-like component with 5 to 7 pins/legs. On the board, look at the transistor cluster group with the heat sink. Google their component number to be sure. If you have LDO then the replacement capacitor selection is more critical. LDO needs capacitors with suitable ESR value to avoid oscillation at its voltage output. You'll need to study the data sheet of the old capacitor (google them) and get new ones with comparable ESR values.
Again, I'm NOT the expert here but these are what I've done to refurbish my ECU. My car was still drivable before I attempted these. Only that I figured the capacitors need replacing after about 20 years of use and some joints might be cracking too.
May these be helpful,
Amarin.
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I envision two approaches.
If your goal is to learn the system you'd build a mockup to substitute for and vary the inputs and measure the outputs such as injector duration so you could pinpoint the fault.
If instead you loathe discarding a piece of your car which might just serve as a spare, you could guess and hope by replacing any components your eye tells you aren't new looking, and try it out. Replacing the electrolytic capacitors reminds me of rebuilding carburetors by replacing the rubber and paper parts -- the wear items. Not a bad gamble.
--
Art Benstein near Baltimore
If at first you don't succeed, skydiving is not for you.
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Thanks for the feed back 😎
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