My Purple Project - SE5a 1973

If you have a long-term project and would like to share/document progress, this is for you.

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rjudcsx
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My Purple Project - SE5a 1973

Post by rjudcsx » Fri Oct 02, 2020 2:21 pm

something scrubs/rubs on full RH lock. Otherwise, smelly, noisy and fun :D Rev-counter has given up & the indicators tell-tales are all but invisible and inaudible; wipers go from left-to-right and the rain stays where it is
[/quote] Adam , I remember it well , your on the home straight now . Regards, Richard .



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adamwilkes
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My Purple Project - SE5a 1973

Post by adamwilkes » Fri Oct 02, 2020 5:32 pm

Just wired up the air-to-fuel ratio meter and Bosch Oxygen sensor; had some variable results; they are - I suspect - the result of a leaking exhaust system; the sensor is after the tailpipe so any air sucked in along the way is noticed, I guess. Here it is, one of the last sections of garden trampoline tubing I have (it's a tight fit using old water-hose onto the tailpipe):

fuel air ratio kit (1).JPG
fuel air ratio kit (1).JPG (241.79 KiB) Viewed 538 times

EDIT: for those who don't know: Air-to-fuel ratio is a measure of the 'strength' of the mixture; a theoretical ideal for complete combustion is about 14.7 parts of air to 1 part of petrol. A richer fuel mix might be 12:1 or lower. A weak mixture would be above 14.7:1. The offside bank on my engine appears to be stuck at 18.5:1 (ie very weak), which I think is a red herring. I think that, normally, our older engines are happier run slightly richer than ideal so maybe 13:1. I await correction on this!


The nearside bank shows a wildly varying fuel strength, as shown:


https://youtu.be/ChqnMiXKnPs


The other side (offside) is steady but very lean (18.5) despite adjustment.
Last edited by adamwilkes on Fri Oct 02, 2020 9:53 pm, edited 2 times in total.


Adam Wilkes
Scimitar GTE 5a 1973, kinda Highland Purple; after months of work, still a ruin!
I can't help myself - I have to ask questions and find out why. Why ? Dunno :shock:
Creator of https://cooldog.uk/

Cutwaterdrummer
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My Purple Project - SE5a 1973

Post by Cutwaterdrummer » Fri Oct 02, 2020 5:58 pm

Shouldn't be any air sucked in through exhaust system as it's under pressure. I used to tune my old GTE in the early 80s using the company's industrial flue gas analyser system (which was very handy!) just by sticking a tube up into the tail pipe. Worked well.


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scimjim
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My Purple Project - SE5a 1973

Post by scimjim » Fri Oct 02, 2020 6:23 pm

Air will be sucked into any leaks between pulses.


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Current: SE5 (8Ball), 1400 1600 1800 Zetec ST170 powered SS1 (G97), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
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Post by philhoward » Fri Oct 02, 2020 6:48 pm

For the purposes on testing on the drive, aluminium (speed) tape will do to seal at each joint.


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Old and Slow
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My Purple Project - SE5a 1973

Post by Old and Slow » Fri Oct 02, 2020 7:09 pm

Well done. must be feeling chuffed !!


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My Purple Project - SE5a 1973

Post by Scim8tar » Sat Oct 03, 2020 1:06 pm

Hi Adam, my first day up and about since being floored by the nasty virus so I am having a go on the forum.
if you get reading's stuck in the 18's even when you add some choke it normally means the sensor is not sampling for some reason, common when they are dying.
When I was experimenting with sniffer pipe's and using the calibrated MOT Ega to check reading's, I found a minimum of 300mm pipe length after the sensor gave best results for low rev's setting's and for road testing (on a deserted road). I use a really long pipe in the garage to keep heat near the sensor and also prevent it getting splashed with condensation as the Bosch 4.9 LSU's are not cheap.
I can post some of the setting that I find give the best performance if you would like.

Paul



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adamwilkes
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Post by adamwilkes » Sat Oct 03, 2020 4:55 pm

Scim8tar wrote:
Sat Oct 03, 2020 1:06 pm
If you get reading's stuck in the 18's even when you add some choke it normally means the sensor is not sampling for some reason, common when they are dying.
Welcome Scim8tar :D Hope you recover fully from Covid :? I wondered about the (brand new) sensor, but when I quickly swapped the sensor pipe assembly from one tailpipe to the other, and back again, the readings were consistently stuck at 18.5 on the right (starboard side), and wildly fluctuating on the port side so I think the sensor is ok still. I have the sensor heater on all the time. The right side manifold is leaking so I may have to knuckle down and tackle that.


Adam Wilkes
Scimitar GTE 5a 1973, kinda Highland Purple; after months of work, still a ruin!
I can't help myself - I have to ask questions and find out why. Why ? Dunno :shock:
Creator of https://cooldog.uk/

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adamwilkes
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Post by adamwilkes » Thu Oct 08, 2020 2:44 pm

Managed a few hours on the Scimitar today - took the wheels to have new tyres fitted :P I don't think vintage 1991 tyres were quite up to scratch really. Anyway, had some low-brow Nankang 185/80 R14's fitted, which look much 'fuller' in the arches than the original (incorrect) 185/70 R14's. There's not much choice in this size these days, and I almost ordered some 195/75's instead (very close to the same diameter but not all that popular either), but decided to go light on the tread-width and see how it feels. Also wound up the front suspension another inch to make the ride height a bit more level (the adjustable Spax spring-nuts now show 21 threads below them); plus I replaced a bracket that holds the bonnet-release spring which had fallen off (corroded rivets).

More importantly, however, I FOUND THE REAR AXLE VENT !! 8) Despite looking through the posts on here, I was still uncertain where the hole was supposed to be, and I took a long time wire-brushing and scraping to find the little blighter. No-one suggested it was on the REAR face of the axle :roll: Some photos are very difficult to interpret - especially when they are published side-on :shock: Ah well, the photos below may help others a little. The vent is about 130mm inboard of the bracketry that is on the end of the right (starboard) side of the rear axle. And it's on the rear of the axle tube. While I was there, I tapped the hole out to M6 (drill out to 5mm first) and fitted a slightly shortened (so it doesn't hit the driveshaft inside) old brake bleeding nipple in there, pushed on a length of soft hose & fed it into the rear cubby-hole. A cable-tie stops it falling out :)

rear axle vent (2).JPG
rear axle vent (2).JPG (127.6 KiB) Viewed 350 times
rear axle vent (1).JPG
rear axle vent (1).JPG (161.65 KiB) Viewed 350 times

I'm glad I found that breather hole, as it's an almost invisible 2-3mm hole when it's been covered in rust and underseal; it is, apparently, important to keep the hole clear so that the differential oil doesn't push past the axle oil-seals when the diff warms up & the oil expands. The white hose I happened to use loops into the rear cubby, so no detritus can enter - I may fit a filter if I come across one :D


Adam Wilkes
Scimitar GTE 5a 1973, kinda Highland Purple; after months of work, still a ruin!
I can't help myself - I have to ask questions and find out why. Why ? Dunno :shock:
Creator of https://cooldog.uk/

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adamwilkes
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Post by adamwilkes » Thu Oct 08, 2020 4:59 pm

Small visual update - new tyres and a second little drive around the block :D It's missing lots of trim (and front bumpers), so it looks a bit 'naked' !

IMG_3385.JPG
IMG_3385.JPG (159.24 KiB) Viewed 328 times

Also fitted a bleeper to the indicators unit, so I know when I am going left or right :lol:


Adam Wilkes
Scimitar GTE 5a 1973, kinda Highland Purple; after months of work, still a ruin!
I can't help myself - I have to ask questions and find out why. Why ? Dunno :shock:
Creator of https://cooldog.uk/

rjudcsx
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My Purple Project - SE5a 1973

Post by rjudcsx » Thu Oct 08, 2020 5:27 pm

Thanks for the pictures of the breather hole ,your car is getting there , wont be long before around the block is a distant memory. Regards Richard .



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My Purple Project - SE5a 1973

Post by scimjim » Thu Oct 08, 2020 7:36 pm

Copied into the how-to/FAQ section.


Jim King

SECURE DRY STORAGE FOR YOUR SCIMITAR

Current: SE5 (8Ball), 1400 1600 1800 Zetec ST170 powered SS1 (G97), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre, TI SS1 (snotty), 1600 SS1 (C686CCR).
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), 1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

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adamwilkes
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Post by adamwilkes » Fri Oct 09, 2020 7:27 pm

Failed rev-counter repair:

Well, the dashboard came out again :shock: From about 3 minutes after fitting the dashboard & starting the engine, the rev counter went all fluttery, then dead. It's been dead throughout the two round-the-block test-drives but now I thought it was time to bite the bullet and sort it out. Wiring looked fine, engine was running so the white wires were good (the white wires feed lowered battery voltage to the ignition coil during running, via the 'Eureka' (resistance) wire); the green (+12v) wire had voltage, and earthing was good. The dashboard and rev-counter needed to come out again.

Many, many thanks to Don Kennedy and his brilliant web pages, particularly this one on rev-counter repairs! https://scimitarweb.co.uk/~donkennedy/r ... ounter.htm

My rev counter had the classic 'failed capacitor' symptom, according to the above webpage. I took the capacitor out and it indeed failed the crucial resistance test - a capacitor should measure infinite resistance (open circuit) between it's legs, perhaps after a brief period of change (depends on the capacitance size). This one measured up at 4.7 Ohms immediately and didn't waver :( Very failed. Capacitors do have a life-expectancy, with some lasting 47 years (this one), others may fail at months old, or just slowly explode after a few years.

Old capacitor:

rev counter repair (1).JPG
rev counter repair (1).JPG (45.23 KiB) Viewed 237 times


New capacitors in place on the circuit board:

rev counter repair (12).JPG
rev counter repair (12).JPG (99.69 KiB) Viewed 237 times


The original capacitor was 2.5uF (micro-Farads), a polarised affair which I replaced with electrolytic (also polarised) types. I'm not sure how critical the value of the capacitor is in this situation; it looks like it may just be there for damping the rev-counter mechanism - a cushioning effect from the ignition-current pulses to stop the needle wobbling furiously so vaguely similar values may be fine. I didn't have a 2.5uF, but made up that value with two 6.8uF and one 10uF capacitors soldered in series. I could get there, so I did :D. Calculated as: 1/(1/10uF+1/6.8uF+1/6.8uF) = 2.53uF. Presto! It verks :D

For those interested, a modified copy of the Dermot Wrycraft circuit diagram on the Don Kennedy webpage, showing the three new capacitors in place of the one failed capacitor:

rev counter repair (13).JPG
rev counter repair (13).JPG (124.37 KiB) Viewed 237 times



rjudcsx
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Post by rjudcsx » Fri Oct 09, 2020 8:47 pm

Adam , I was ok up to the end of the second paragraph , then the fact that I went rowing instead of Physic lesson's [ in fact, most lessons ] kicked in. However, I will show it to my friend who owns a couple of electrical outlets and he will enlighten me, so, no criticism intended and thank you for a bit more info I will use to mend my Rev counter .Regards, Richard .



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adamwilkes
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Post by adamwilkes » Fri Oct 09, 2020 9:11 pm

Richard, if you have a dead rev counter and the wiring is all good, grab a 2.2uF electrolytic capacitor - the 2.5uF seem to be hard to find. Ebay sell them - for example a 2.2uF at https://www.ebay.co.uk/itm/Electrolytic ... SwDSRch6UB. Find the little grey sausage on the pcb inside & have your friend replace it :D

By the way, I also did rowing (for a few months) - it was the greatest training workout I have ever tried; highly recommended :D But I did enjoy physics too :shock:
Last edited by adamwilkes on Fri Oct 09, 2020 10:34 pm, edited 1 time in total.


Adam Wilkes
Scimitar GTE 5a 1973, kinda Highland Purple; after months of work, still a ruin!
I can't help myself - I have to ask questions and find out why. Why ? Dunno :shock:
Creator of https://cooldog.uk/

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