Won't Start - Page 5

urquattr085 · 11-09-20, 08:08 PM

Quote:

Originally Posted by BackintheFold

I...I....I....
I think it’s fixed.

Ready for the solution?

Cam caps were loose. Well, the nuts were loose. Finger right only, held in place by pressure from the valves!

There was also one other thing I’d noticed recently when peering down the dizzy hole. The cam gear looked like it had been LIGHTLY hammered. Or rolled along a concrete slab. Very very lightly damaged at the top of the cam gear.

The loose camshaft must have been able to flex up when under acceleration and skip a few teeth until the eco cut out the ignition.
Explains all symptoms and also the gentle chattering damage in the cam gear!

Taken out for a spin and all performed faultlessly. Fortunately didn’t have to remove bumper etc for retiming.
No mission creep, but a couple more jobs now.
Need:rear left ABS sensor.
Front wishbone bushes.
More on that later...

Really pleased you've found the issue - bit of an odd one though.!!

urquattr085 · 12-09-20, 12:27 PM

Quote:

Originally Posted by BackintheFold

ABS - am getting a sine wave reading rather than a square wave from that sensor. Before I try to adjust it, I’d like to
Have a spare to
Hand-and I don’t have a spare. If it turns out not to be the sensor I will be able to keep a spare.

Just a thought, could the output issue be down to corroded reluctor ring teeth?

The rear sensors are both the same, so you could swap in the other sensor & re-test the output if you are getting a square wave from it in its original position. It would confirm if its a sensor issue.

Hanuman · 13-09-20, 08:22 AM

If you’re getting an actual waveform output, then I’d say the sensor is able to detect just fine. (What equipment are you using to monitor the waveform?)*
Unless you are certain the rings are perfect, and gap settings correct, that’s where I’d be looking. The teeth clog up with road grime, grease and rust. The ablative caps, too.
The rings aren’t impervious to rust. Easily replaced for £10 or so. I did one on mine, on the car, not so long ago. Probably easier done on the bench.

You’d be surprised at how well the system works with badly degraded rings. It’s my experience that as long as there is a discernible signal output for the ABS controller to compare, you should be ok.

Orientation of the sensor might have an effect. As would happen distance. Ablative caps have been reproduced. They’re no longer priced as if a disposable item, sadly.
Be careful if inserting the sensor without a cap. It can be done, but your first indication of contact with the rings is wearing away the blade tip of the sensor. As the idiots in wales helped me discover. One of my sensors has a very badly damaged tip. The system still functioned fine.

Where is the signal being measured? At the cable joint, or at the main plug/socket on the ABS controller.
Don’t discount 1980s quality electronics and dry solder joints.

BackintheFold · 13-09-20, 10:45 AM

I’m using a small oscilloscope to measure the outputs at the ABS ECU plug.
It may be a matter of adjusting the sensor. It may be a crud filled ring.
To fix either I will need to remove the sensor, clean the ring through the hole and refit it
while checking the output. I don’t want to remove the shaft to check the ring.
I want to have a spare sensor to hand in case I break the old one when removing it. I can tap it back in mm by mm, stopping when I get the square signal I need.
Orientation is fixed by the mounting which is still in one piece, so that’s one less thing to worry about!

Hanuman · 13-09-20, 12:06 PM

what behaviour were you getting that led you to suspect the sensor?

Colin Aitchison · 14-09-20, 06:38 AM

You have been very lucky, loose cam caps!!! You need to have a look at the shape of the upper cam caps on all four, also, timing belt tension, not to mention the possibly that the oil pressure would have been very low in the engine due to the cam bearing having an oil feed to each one.

BackintheFold · 14-09-20, 08:50 AM

Quote:

Originally Posted by Hanuman

what behaviour were you getting that led you to suspect the sensor?

at slow speeds, a chattering from the pump. Consistent with one sensor being "off". At high speed, no problems.
I think i started a thread on that a while back-I'll go back there and update when i next get a chance to look at it.

BackintheFold · 14-09-20, 08:54 AM

Colin:
Not loose as such, just not tight!
I was working on the car with the help of an ex-BA mechanic with a HUGE amount of experience on engines-including DeLoreans as a side note-and he inspected the caps and was happy they were undamaged.
We took the opportunity to fit a new camshaft oil seal, and the timing (and belt) is reset spot-on.
I'd been keeping an eye on oil pressure recently too, and it was not exactly off the scale, but well within specs.

An odd one for sure, and now i know what the problem was, a test would have been to try and lever up the camshaft through the dizzy hole. There may have been a little movement detectable there which would have been a massive clue!

urquattr085 · 14-09-20, 08:19 PM

Quote:

Originally Posted by BackintheFold

I was working on the car with the help of an ex-BA mechanic with a HUGE amount of experience on engines-including DeLoreans

Now he sounds like a handy fella to know.

Sounds like you've done all the right things.

Hope you can also get your abs sorted. My sensors weren't too bad to remove after plenty of penetrating oil over a week or so. I no longer renew the caps, like you I use a scope to match outputs from different wheels.

13-09-20, 08:22 AM	#43
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	If you’re getting an actual waveform output, then I’d say the sensor is able to detect just fine. (What equipment are you using to monitor the waveform?)* Unless you are certain the rings are perfect, and gap settings correct, that’s where I’d be looking. The teeth clog up with road grime, grease and rust. The ablative caps, too. The rings aren’t impervious to rust. Easily replaced for £10 or so. I did one on mine, on the car, not so long ago. Probably easier done on the bench. You’d be surprised at how well the system works with badly degraded rings. It’s my experience that as long as there is a discernible signal output for the ABS controller to compare, you should be ok. Orientation of the sensor might have an effect. As would happen distance. Ablative caps have been reproduced. They’re no longer priced as if a disposable item, sadly. Be careful if inserting the sensor without a cap. It can be done, but your first indication of contact with the rings is wearing away the blade tip of the sensor. As the idiots in wales helped me discover. One of my sensors has a very badly damaged tip. The system still functioned fine. Where is the signal being measured? At the cable joint, or at the main plug/socket on the ABS controller. Don’t discount 1980s quality electronics and dry solder joints. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

13-09-20, 10:45 AM	#44
BackintheFold Senior Member Classic Audi Club Member Join Date: Feb 2019 Location: Near an MB ur Quattro Posts: 1,171	I’m using a small oscilloscope to measure the outputs at the ABS ECU plug. It may be a matter of adjusting the sensor. It may be a crud filled ring. To fix either I will need to remove the sensor, clean the ring through the hole and refit it while checking the output. I don’t want to remove the shaft to check the ring. I want to have a spare sensor to hand in case I break the old one when removing it. I can tap it back in mm by mm, stopping when I get the square signal I need. Orientation is fixed by the mounting which is still in one piece, so that’s one less thing to worry about! __________________ 2006 A3 (daily drive) 1987 MB ur Last edited by BackintheFold; 13-09-20 at 10:50 AM.

13-09-20, 12:06 PM	#45
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	what behaviour were you getting that led you to suspect the sensor? __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

14-09-20, 08:54 AM	#48
BackintheFold Senior Member Classic Audi Club Member Join Date: Feb 2019 Location: Near an MB ur Quattro Posts: 1,171	Colin: Not loose as such, just not tight! I was working on the car with the help of an ex-BA mechanic with a HUGE amount of experience on engines-including DeLoreans as a side note-and he inspected the caps and was happy they were undamaged. We took the opportunity to fit a new camshaft oil seal, and the timing (and belt) is reset spot-on. I'd been keeping an eye on oil pressure recently too, and it was not exactly off the scale, but well within specs. An odd one for sure, and now i know what the problem was, a test would have been to try and lever up the camshaft through the dizzy hole. There may have been a little movement detectable there which would have been a massive clue! __________________ 2006 A3 (daily drive) 1987 MB ur Last edited by BackintheFold; 14-09-20 at 10:50 AM.

14-09-20, 06:38 AM	#46
Colin Aitchison Senior Member Classic Audi Club Member Join Date: Dec 2013 Location: Back home in Tillicoultry Posts: 1,308	You have been very lucky, loose cam caps!!! You need to have a look at the shape of the upper cam caps on all four, also, timing belt tension, not to mention the possibly that the oil pressure would have been very low in the engine due to the cam bearing having an oil feed to each one.