Low tension circuit questions
Moderators: scimjim, Lukeyboy46, erikscimitardemon, Roger Pennington, philhoward
Low tension circuit questions
I am investigating an annoying misfire at low speed/tickover on my SE5.
I measured the voltage at the +ve lead going onto the coil and I'm getting 12.5 volts.
I thought this a bit odd as I assumed it would have a ballast wire fitted in the loom.
When I fit the wire on the coil with the ignition on I get 5.5 volts,but when I open the points
or remove the -ve wire from the coil I get 12.5 volts again.
Any thoughts?
Nick
I measured the voltage at the +ve lead going onto the coil and I'm getting 12.5 volts.
I thought this a bit odd as I assumed it would have a ballast wire fitted in the loom.
When I fit the wire on the coil with the ignition on I get 5.5 volts,but when I open the points
or remove the -ve wire from the coil I get 12.5 volts again.
Any thoughts?
Nick
- philhoward
- RSSOC Member
- Posts: 24247
- Joined: Tue Aug 29, 2006 5:41 pm
- Location: Staffs, UK
- Has thanked: 43 times
- Been thanked: 539 times
- Contact:
Low tension circuit questions
Sounds like your coil is too low a resistance compared to the ballast resistor (wire).
Phil Howard
Scimitarweb Forum Admin
SS1 1600 Rooster Turbo; Sabre Mk1.5, Sabre Mk2
Previous: SE5/5a/SS1 No.1/SS1 Rooster/SS1 1800Ti/SE5a 24 Valve
http://www.ss1turbo.com
Never try and argue with an idiot. They drag you down to their level, then beat you based on experience.
Scimitarweb Forum Admin
SS1 1600 Rooster Turbo; Sabre Mk1.5, Sabre Mk2
Previous: SE5/5a/SS1 No.1/SS1 Rooster/SS1 1800Ti/SE5a 24 Valve
http://www.ss1turbo.com
Never try and argue with an idiot. They drag you down to their level, then beat you based on experience.
- AJL Electronics
- RSSOC Member
- Posts: 7554
- Joined: Fri Oct 17, 2008 8:49 pm
- Location: Gloucester
- Has thanked: 42 times
- Been thanked: 212 times
- Contact:
Low tension circuit questions
9V will be the average Voltage with the engine running.
Yes, we can mend your Scimitar!
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
- AJL Electronics
- RSSOC Member
- Posts: 7554
- Joined: Fri Oct 17, 2008 8:49 pm
- Location: Gloucester
- Has thanked: 42 times
- Been thanked: 212 times
- Contact:
Low tension circuit questions
Not with a digital meter please, unless you strap a big electrolytic across the terminals of the meter.
Yes, we can mend your Scimitar!
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
- David Tew
- RSSOC Member
- Posts: 367
- Joined: Sun Aug 06, 2006 11:09 am
- Location: Cotswolds
- Has thanked: 6 times
- Been thanked: 26 times
Low tension circuit questions
The 12.5v is a bit of a red-herring as that is your full battery voltage. With the coil +ve connected and either the coil -ve disconnected or the points open you will get full battery voltage on the coil +ve even with the ballast in circuit as there is no circuit back to the battery -ve.
5.5 volts from the ballast sounds a bit low to me. Phil's suggestion of the wrong coil is a good one. It could also be a high resistance ballast/eureka wire.
5.5 volts from the ballast sounds a bit low to me. Phil's suggestion of the wrong coil is a good one. It could also be a high resistance ballast/eureka wire.
SE4B Coupe - rebuilt on brand-new chassis.
RSSOC member since 1978. 😲
RSSOC member since 1978. 😲
- AJL Electronics
- RSSOC Member
- Posts: 7554
- Joined: Fri Oct 17, 2008 8:49 pm
- Location: Gloucester
- Has thanked: 42 times
- Been thanked: 212 times
- Contact:
Low tension circuit questions
With the engine not running, the Voltage is of academic interest only. The points dwell angle will determine the Voltage that appears when running and that Voltage is the only one that needs to be concerned about. The exact Voltage is less important as it will vary with terminal Voltage on the battery.
Yes, we can mend your Scimitar!
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
- scimjim
- RSSOC Member
- Posts: 36360
- Joined: Sun Oct 01, 2006 10:08 pm
- Location: Gloucester
- Has thanked: 115 times
- Been thanked: 853 times
Low tension circuit questions
I found a problem with my dizzy cap simply by putting a timing light on each lead in turn - showed an intermittent pulse on several cylinders.
Jim King
Current: SE5 (8Ball), TI SS1 (snotty), 1600 SS1 (G97), 1600 SS1 (C686CCR), 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
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), Sabre/MX5 auto (The Flying Broomstick),
1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS
Current: SE5 (8Ball), TI SS1 (snotty), 1600 SS1 (G97), 1600 SS1 (C686CCR), 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
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), Sabre/MX5 auto (The Flying Broomstick),
1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS
Low tension circuit questions
So using a digital multimeter with the engine running is a no no?
I will try a timing light for each cylinder and see what I get.
The engine runs perfectly when some throttle is applied,but it runs like a pig through town
when I am hardly touching it.
I even swapped my twin carb set up for a single as I thought it might have been a carb issue
and dropped the pressure on my fuel reg,but it made no difference[apart from losing a chunk of performance].
I will try a timing light for each cylinder and see what I get.
The engine runs perfectly when some throttle is applied,but it runs like a pig through town
when I am hardly touching it.
I even swapped my twin carb set up for a single as I thought it might have been a carb issue
and dropped the pressure on my fuel reg,but it made no difference[apart from losing a chunk of performance].
- AJL Electronics
- RSSOC Member
- Posts: 7554
- Joined: Fri Oct 17, 2008 8:49 pm
- Location: Gloucester
- Has thanked: 42 times
- Been thanked: 212 times
- Contact:
Low tension circuit questions
The response of a digital meter is too fast for a square wave source. The needle of a proper meter integrates the pulses and gives an average.
Yes, we can mend your Scimitar!
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
- AJL Electronics
- RSSOC Member
- Posts: 7554
- Joined: Fri Oct 17, 2008 8:49 pm
- Location: Gloucester
- Has thanked: 42 times
- Been thanked: 212 times
- Contact:
Low tension circuit questions
I think you need to go back to basics with a dwell angle and timing check, plus looking at plugs and HT leads. Then a brake cleaner test on the manifold and carburettor gaskets. A compression test would also be interesting.
Yes, we can mend your Scimitar!
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
-
- Posts: 14
- Joined: Sun Nov 11, 2018 1:13 am
- Been thanked: 1 time
Low tension circuit questions
Like RMS?AJL Electronics wrote: ↑Thu Nov 22, 2018 8:51 pmThe response of a digital meter is too fast for a square wave source. The needle of a proper meter integrates the pulses and gives an average.
1597 [+ .005] cvh with kent Kccv23 cam living in a heavily worked and skimmed head fed by twin 40's fueled by home made leaded 5* plus...XR2 gearbox rebuilt by abbey with 4.29 final drive.....sitting in the back of Jeremy Phillips 2nd development Mojo....
- AJL Electronics
- RSSOC Member
- Posts: 7554
- Joined: Fri Oct 17, 2008 8:49 pm
- Location: Gloucester
- Has thanked: 42 times
- Been thanked: 212 times
- Contact:
Low tension circuit questions
Yes, a bit like RMS!Kccv23highliftcam wrote: ↑Fri Jan 11, 2019 12:32 pmLike RMS?AJL Electronics wrote: ↑Thu Nov 22, 2018 8:51 pmThe response of a digital meter is too fast for a square wave source. The needle of a proper meter integrates the pulses and gives an average.
Yes, we can mend your Scimitar!
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).
Fancy a holiday in Gael, France? http://www.ianrhu.com
There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.