Zel's Fleet Blog...Lada, Saab, Citroen, Sinclair & AC Model 70

Post pictures and stories about your cars both present and past. Also post up "blogs" on your restoration projects - the more pictures the better! Note: blog-type threads often get few replies, but are often read by many members, and provide interest and motivation to other enthusiasts so don't be disappointed if you don't get many replies.
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Atodini
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Location: Mansfield Notts.
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Re: Zel's Fleet Blog...Lada, Saab, Citroen, Sinclair & AC Model 70

#51 Post by Atodini » Thu May 10, 2018 7:10 pm

I would replace the lambda as well..... The out of range earth reading would trouble me more than a tad. Earth errors cause all manner of problems on "moderns"!!

Quick question - did you clear the fault code before testing the voltage? Most ecu's, if they detect a faulty sensor or similar, disable the input, then the fault code is generated and logged. They refuse to "talk" to it again until the fault is cleared...... So even when the fault is rectified the affected sensor won't even be monitored until the ecu is reset, so the problem will not be cleared.

John
"I thought I was wrong once - But I was wrong"...

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Zelandeth
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Re: Zel's Fleet Blog...Lada, Saab, Citroen, Sinclair & AC Model 70

#52 Post by Zelandeth » Thu May 10, 2018 7:36 pm

The ECU was left disconnected from the power supply overnight so any stored codes would be wiped. Sadly no change when it was powered up. The fault is definitely here with the ECU rather than the sensor.

With the lambda sensor disconnected there should be a 500mV reference signal visible on the signal line from the ECU, that's way out of whack (at 0.7V, verified both with a digital and analogue meter). The sensor itself still seems to measure OK, though as you say it may well make sense to get a new one ordered. Sadly I can't swap it on the driveway really as I can't get any of my tools onto it because of the proximity of the steering box and chassis rail...it's an "access from underneath on the 4-post lift with fancy garage tools job" really. I played that game when changing the last one.

I still seem to have heater continuity though, and the sensor side looked OK based on what I was seeing on the meter...It's not grounded at the sensor end (unlike the lambda sensor used by the carb cars, which used the exhaust system as the ground path) anyway, so I think it may have survived as there wasn't any excessive voltage seen between the two sides of the sensor, if that makes sense - the levels were just offset with respect to vehicle ground.

At least with an ECU with a working check engine light in place it's easy enough to diagnose a duff sensor. If the input goes out of range it will trigger it (code 13: No oxygen sensor signal, 44: Lean exhaust condition or 45: Rich exhaust condition). You can actually watch the lambda behaviour in real time with the system in diagnostic mode as well, just using the light. One of the reasons I've been wanting to use this injection system from square one is that there's really good documentation out there for it - hence how I was quite quickly able to track down the wacky earth shenanigans earlier in this thread.

Toledo Man
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Re: Zel's Fleet Blog...Lada, Saab, Citroen, Sinclair & AC Model 70

#53 Post by Toledo Man » Sun May 20, 2018 8:35 pm

Zel, you should check out Hub Nut on YouTube. He's none other than Ian Seabrook, editor of Classic Jaguar magazine. He's got an Invacar back on the road. I remember these back in the day. I don't suppose your Lada has an OBD port by any chance? With the right software, you could see if a laptop can talk to the ECU. Isn't it possible to have your ECU repaired?
Toledo Man

1972 Triumph Dolomite 1850 auto (NYE 751L) - The rolling restoration.
2008 Citroen Grand C4 Picasso 2.0 HDi Exclusive (MA08 WCL) - The modern.
2004 Vauxhall Vectra Club 1.8 16v (ML54 JJF) - Don't ask!

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JPB
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Re: Zel's Fleet Blog...Lada, Saab, Citroen, Sinclair & AC Model 70

#54 Post by JPB » Sun May 20, 2018 11:11 pm

Toledo Man wrote:
Sun May 20, 2018 8:35 pm
Isn't it possible to have your ECU repaired?
I've done a few, the difficulty is separating the components without damage to leadouts and to the vias on the board as you try to chip away the resin. As for newer ones where many more components are surface mounted, they'll lead you down the road to clinical insanity. :evil:
Easiest are some of the early '80s units, which are often potted in pitch. A good overnight soak in petrol should provide access to everything.
John

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Zelandeth
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Re: Zel's Fleet Blog...Lada, Saab, Citroen, Sinclair & AC Model 70

#55 Post by Zelandeth » Mon May 21, 2018 5:58 pm

I'm well aware of the gent behind the Hubnut videos, it was in fact his thread about reviving his Invacar which introduced me to the fact that they existed. I am *hoping* that I might be able to have mine on the road in time for it to be on show alongside his one at the Festival of the Unexceptional. Time will tell...there are quite a few things going on behind the scenes though.

The Lada's ECU does have a diagnostic port, though it uses the ALDL protocol rather than OBD or OBDII, it is actually the direct predecessor to what became the OBD protocol. Designs for how to make a serial PC interface are readily available online. This will then allow a suitable package (an older version of EFiLive for instance) to speak to it.

I do plan to attempt to repair this one, though it's going to be far easier to do once I have a known good one to compare to. The issue with mine I'm pretty sure is simply a failure of one or two transistors, though the headache is that the ones in there have custom part numbers on - so it's really hard to figure out what they are. With a known good ECU to hand, hopefully I'll be able to work it out.

Not expecting the physical side of the repair to be too hard, the traces and components are huge compared to some repairs I've done before, the only real headache is the really thick conformal coating that the board is coated with.

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