Classic Car PCB component degradation faulting - what should we look for?

I have a passion for 60s & 70s classic cars. I've also two from the late 80s & 90s. Problem is these are from the era of electronics, and their PCBs don't seem to last.

Pix show a PCB which up until recently would retain its fuelling config. settings in memory at engine OFF. No more. The only cure is to re-config. via my ancient Win98 laptop. This is not viable.

The PCB is mid 90s vintage. Looking at the pix can anyone hazard as to which components are failing? I'm hoping it's a simple swap of the capacitors. Would they hold the memory at power-down or am I in real fix 'cos it'll be the processor chips themselves?

This sort of thing is going to be a real issue for what are now starting to be considered 'modern classics'.

The space-bar on my laptop plays-up. Sorry for typo in this post's header.

 

Welcome to AAC.

Without being able to do any diagnostics on components - my guess - I said "GUESS" - would be a faulty memory chip. Back in the 80's and 90's memory chips MIGHT look like the rectangular chip (24 leads) on the left of the picture. But without being able to do any diagnostics on it - guessing is all anyone can do.

None of the capacitors appear to have bulged, but that doesn't always mean a cap is good. It may have dried out. But I would suspect that the caps are not there to hold the memory. I didn't see a battery either, such as a CR2032, which could be used to hold the memory in its last state. Non-Volital memory chips became the norm back some time but I can't be sure of when they first appeared. Before then I remember memory chips with batteries built right on top of the chip.

Bottom line, unless you have the skills and tools to do a full diagnostic examination on the board, or you know where you can take it for examination there's nothing I can see just by looking at it to help figure out why it's not holding the last setting.

 

Thank you for your help. Frankly that was the answer I was expecting. Whereas, I was hoping you'd say "Yup... caps are cheap as chips, aaaaaand I suspect they hold the power for memory, you'd be daft not to try - change them and be lucky."

Seems a lot of 90s classic cars are set to meet the 'great scrap-pile in the sky' for want of this sort of thing. Fortunately in this instance there's a way round it.

 

Number one, look very closely with a magnifier for any fractured solder joints. The vibration does cause troubles there, especially at the connector and big through-hole parts.
Next is electrolytic capcitors don't last forever, the lone black one looks suspect.
You can follow the connector pins for which pin goes to the battery and see how the board is powered - Is the NV memory of the "fuelling config settings" from RAM the car battery powers or is it in MCU EEPROM?

You might just be changing the calibration memory and not saving it...

 

I am confused about the meaning of the term "fuelling config settings" to begin with. WHAT does that mmean??

 

Aftermarket Computers are everywhere today,
do You understand enough about Engine-Operating-Requirements to do the required programming ?
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I looked and it's not OEM or "classic car" at all. "OMVL Millennium lambda control system AEB175 with a 2-position change-over switch and loom, as well as the control box and stepper motor."

Some kind of LPG gas controller with the stepper motor. I can see a PIC MCU.

 

Number one, look very closely with a magnifier for any fractured solder joints.

Don't know why I didn't consider that. It's been a reason for lots of failures. Neighbor (elderly) had a sprinkler controller go bad. Some young man wanted to take advantage of her and sell her a new one for $500. You can get them at the big box stores for under $100 with up to 9 zones. Before he could rob her I asked if I could take it home and look at it. When I did the failure was extremely obvious; the multi position rotary switch used for programming had been handled so much that the solder joints had fractured. Simple reflow of the solder with just a small amount of flux made the joints like new. The controller is still working just fine and it's been about 10 years now. Of course, she doesn't (or didn't) handle the controller very often other than to shut it off for the winter and turn it on in the springtime.

I also glanced at the Electrolytic Caps (EC). I didn't notice any bulging. But not all caps fail and bulge. An easy replacement of the caps - proper value, voltage and size "Might" solve the problem. But I'm more of the opinion that it may be a non-volatile memory chip has gone bad. You DO know memory chips have a limited number of times they can be written and rewritten to.

 

There was a worldwide rash of bad Electrolytic capacitors back then.
This was a Canon E40 video camera after they charged me $250.00 to fix it. The caps were just rattling around inside it.

"Electrolytic caps can leak and still work, so the product may work for some time before it stops working completely. You can tell because usually you see several caps that have leaked when you take something apart and the chances are slim that they all started leaking at the exact same time."

 

Sorry, should have said: The term "fuelling config settings" for the purposes of this thread are the settings stored to memory on the chip or.... I hope... to memory powered by easily swapped-in Caps.

I'm going to give this a bash. If I'm lucky this is a few capacitors and a re-flo of one or two dodgy joints.
Er no, it's not strictly any OEM part. Correctly idenified as a CNG/LPG gas controller with the stepper motor. A fuelling gizmo first made in the late 80s and sold into the 90s. Used on classics. It's suited to fuelling carb. vehicles. Currently in use on a 1960s Land rover. Worst case, if I fail to cure things, I can cobble up a CR2032 and a few diodes into the 5V rail. I think... I know how to do that. The PCB has a switched 12V input and a 'perm. live' 12V input to a 7805.

I didn't know I can't jsut keep pumping new config. settings to memory on chips like these, thank you.

To my wider point. If things like Caps degrade at this age, many cars in the era of this PCB will go.

 

How many times can I store to memory on such chips? At the moment I must do this often just to get the engine to fuel and run.

 

Why would You want to try to fix something that wasn't all that great when new,
and now is basically worn-out, and problematic, by your own admission ?

It's unlikely that,
after all the time You will spend trying to patch-it-up,
that You will have reliable transportation.

Is there a good reason to keep the ancient Propane-System ?
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The AEB controller is not great, but all well enough. Been running them for 11-12 years, I've got several that work fine. This is the first with this issue. I want to sort it if I can; purely because the rest are likely to meet the same fate - I like to drive my classic. I have spares for everything. I do 9-10K a year - rain or shine,but less since COVID. Let's be real, my Land rover is always the worst vehicle on the road - every vehicle I meet for miles is better suited to the job, and by a country mile... it's 'orrible. You either get the classic-car thing or you don't. For me, if I wanted it to be reliable, well... what would I do with my time if I wasn't fixing it?

This is just another side to it, "it's my 'thing' ". People always let you out, children wave. I put modded to fit discs from drums last year. It's endless, and none of it makes a jot of sense.

 

As for the Propane - more strictly Methane here.... once you're aware of Brit petrol prices it's the one thing in this that makes perfect sense. Fuel is kinda' given away for tuppence ha'penny Yankside.

 

As well as the caps, another possibility is a small soldered-in rechargeable battery (eg NiCad in the old days) that has died a natural death and needs replacing. Before the era of EEPROM chips a trickle charge from a battery maintained the memory.

 

There's no cells on the board. As above, may add some.

 

Certainly the TS is correct about petrol pricing in the UK. Vastly greater than here in the US. At least that was a bunch of years back, and I can't imagine it is better today.
Here it is the opposite. I have a standby generator setup for three fuel operation, gasoline, LPG, and natural gas. The cost of propane at $20 for enough to run 5 hours is a lot more than for the gasoline to run that same 5 hours.

 

Not looked lately - UK petrol comes in 2-3 pricier than the US petrol when I looked. Hence gas makes sense.

I'm stuck with this relatively vintage fuel control system because anything in production today is designed around today's cars. Multi-point injection/direct injection, not carb. Hence no petrol injectors to trigger my 'fuel-control' PCB or gas injectors to fire.

 

The one propane fuel system I investigated used a regulator that was magically piloted by the manifold vacuum, and somehow also adjusted by engine RPM. I also supported a research project for analog control of the petrol delivery to a spray bar above the throttle blades. That project used an analog computer to set the fuel flow. So certainly a totally analog scheme can actually work. But for production they did scrap analog and used a digital system that used air flow, throttle position, and RPM to control fuel delivery.

 

Classic Car PCB component degradation faulting - what should we look for?

I have a passion for 60s & 70s classic cars. I've also two from the late 80s & 90s. Problem is these are from the era of electronics, and their PCBs don't seem to last.

Pix show a PCB which up until recently would retain its fuelling config. settings in memory at engine OFF. No more. The only cure is to re-config. via my ancient Win98 laptop. This is not viable.

The PCB is mid 90s vintage. Looking at the pix can anyone hazard as to which components are failing? I'm hoping it's a simple swap of the capacitors. Would they hold the memory at power-down or am I in real fix 'cos it'll be the processor chips themselves?

This sort of thing is going to be a real issue for what are now starting to be considered 'modern classics'.

The space-bar on my laptop plays-up. Sorry for typo in this post's header.

I would check the blue 100ohm resistor left to the heatsink and the smd below it in series. I think I see a burn mark...