Hello everyone,
I am now in the final steps to crank my 52 years old S1 but I am facing a strange thing: no ignition, no spark, no nothing !
I have changed HT coil, ballast resistor, condensator, points, spark plugs. 12 volts are arriving to the HT coil, HT leads has been changed and still nothing. A little help would be welcome and if anyone has the procedure to check ignition components, it could be awsome !!
In the meantime I’m stuck !!
Thanks for your help
How about 12v at the points??
**
With the engine standing, ign ‘on’ you should have 12V on both coil ‘+’ and ‘-’, Bertrand…
If not; either the coil primary has failed; disconnecting leads on either ‘+’ or ‘-’ and measuring ohms over the coil - you should read somewhere between 1 and 3 ohms. High resistance means brake in primary - replace coil…
The general test; connect a test lamp between coil ‘-’ and ground. With ign ‘on’ the lamp should be fully lit; while cranking, the lamp should dim and flicker - indicating that the points ‘make’ and ‘break’ coil ground.
If this checks out OK; disconnect coil center lead from dis lid and hold the lead 1/4" from a good ground - while cranking you should have a strong, blue spark. If ‘no’, change coil. If ‘yes’; remove dist lid and inspect/change rotor - and ensure that the rotor rotates while cranking.
As the points close, current is running through the coil, charging it - as the points starts to open, the coil deliver ignition voltage. Which goes through the rotor to the plug lead adjacent to the rotor - and the plug sparks. In theory; if the rotor fails to conduct, or if the rotor is between two tabs on the lid (incorrect ign timing) - the plugs will not fire.
Ie, if the center lead sparks but not the plugs; it’s a connection problem between the coil and the plugs. If the center lead does not spark; it’s a coil or a points/power problem…
Frank
xj6 85 Sov Europe (UK/NZ)
You’re car most likely also has a relay on the firewall that bypasses the ballast resistor to ease cold starting. This only operates during cranking so it could have failed (or be connected wrong) so that you see 12v at the coil etc… before you crank with ignition on but it losses it during the start procedure while cranking.
You could simply provide a temporary 12v wire directly to the positive side of the coil bypassing the relay, ballast resistor and their associated wiring and see if you get a spark when cranking then.
BTW if it happens to start don’t let it run that way too long - coil needs the ballast resistor for prolonged function or it’ll burn out.
Bertrand,
what is the general condition of the car in general (original or molested, in state of restoration etc.) and the electric circuits in particular: battery new or known good, ignition lock? - What happens, if you turn the key? Do accessories work, do headlights work, do you see the idiot lights with ignition on, finally does your engine crank, but simply refuses to fire?
If all the aforementioned work, do as Frank has advised - just follow the power! Up to the coil you should see 12 V, on the HT side you should check with a spark plug.
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
Hi Jochen,
The car is in a quite good condition, no modification, and the harnesses are in good shape even though I had to replace lucar connectors here and there the most “damaged” wires are the ones located on the firewall “cooked” by the engine heat. Accerories are working but the washer pump, idiot lights are there, the engine crank bur does not fie… I’ll try Frank’s trick to investigate where the problem comes from
Thanks
Thanks Frank for your tips I’ll try this and let you know !
Hi Frank,
Well I ran some measurments again and I checked the voltage on the coil w/ and w/o contact ignition.
As expected w/o contact 0V everywhere
When contact is on I get the following values on the HT coil connectors
Hi again Frank,
I’ve just notice that some of the characters have been mofied in my previous message please read the following:
Contact Ignition on:
Positive to ground 5.98V
Negative to ground 0.7V
Positive to negative 5.45V
Sorry for that
Bertrand
Hi Carl,
Between which points should I check voltage ?
Thanks
Bertrand
Hi Jochen,
Well I ran some measurments again and I checked the voltage on the coil w/ and w/o contact ignition.
As expected w/o contact 0V everywhere
When contact is on I get the following values on the HT coil connectors
Positive to ground 5.98V
Negative to ground 0.7V
Positive to Negative 5.45V
Hope you can lead me toward an explanation/solution
Thanks
Bertrand
Bertrand.
I presume that your car is ewuipped ewith point and condensor ignition. Remove the distributor cap. Teh points open and close to charge the coil. Witht he key on onen and cose, is the spark there
Thanks Carl,
Yes my car has a genuine coil/points/condensator ignition design
As mentioned in my previous message voltages measured are not right and I have to understand why/where the problem is. without 12V on the coil, I won’t get any spark !
Any suggestion is welcome
Bertrand
Bertrand, you should have 12v at the sw( or+ve) terminal of the coil. If not, disconnect the wire from the terminal and see if you now have 12v ( battery voltage) This is supplied from the ignition switch possibly via the ballast resistor if fitted. The 12v is applied to the coil which is a 10v unit ,whilst cranking; after the engine fires, the feed is via the resistor which drops the running voltage back to 10v so as not to burn out the coil. The CB ( circuit breaker or -ve) lead goes to the points and should either be a straight short to earth if the points are closed or open circuit if points are open , this measured from the wire to the distributor with the wire disconnected from the coil. If those 2 conditions are met, test for spark doing the following; remove the central ignition lead from the dist cap and hold it near the engine (earth) So you have the HT lead from the coil near the engine. If you manually open and close the points or crank the engine, that lead should spark to earth every time the points open. If so, your issue is further downstream ( dist cap, leads, plugs etc) if not upstream, power from ignition switch or ballast wiring.
Good luck.
weird readings
Franks instructions were spot on
a test light is very helpful for this situation, $10 will get you one
some quick easy tests:
(you say you have verified at least 12.5V at battery terminals ?), try turn the headlights on etc, if so
If you have no spark,
If still no spark, these 2 tests will narrow the faults down to bad coil, bad condensor or points, or very few bad wires
Its also somewhat possible based on your readings that you have a partial short to ground somewhere
Per the other learned guys I would run a direct wire from battery to coil, removing the normal car supply wire. I had this issue several years ago with my Series 1 when recommissioning. The car would try to fire while cranking only to die when the key released. The ballast circuit was not operating - provides lower voltage so as to preserve coil etc. As others say 12V wont worry the coil whilst you are troubleshooting.
**
You sure won’t get ignition with those readings, Bertrand…
Fundamentally, voltage drops from battery voltage implies that a current is flowing through a resistance. Without the engine turning, points open; there should be no current flow. First step, as Kevin says; disconnect coil ‘+’ wire from coil, and measure voltage on the (disconnected) wire - you should read battery voltage.
If so; either the points are closed, and turning the engine a bit may open them - and the coil ‘+’ and ‘-’ should then show 12V (battery voltage), However, as you have no ignition while cranking it’s likely more to it than that - and verifying, as Kevin says, whether the points open and close as they should. Are you sure the points gap is set correctly? The (disconnected) coil ‘-’ wire should indeed read ‘0’ ohms, points closed, and ‘1’ with the points open - if reading ‘0’ in either, there is a short, failed or misconnected condenser or whatever…
Of course, if the (disconnected) coil ‘+’ reads in the ‘5V’ range; there is a problem with the feed wire from the ign switch. If so; leave the coil ‘+’ wire disconnected and, as Tony says; jumpwire battery ‘+’ directly to coil ‘+’ - and try starting…
Frank
xj6 85 Sov Europe (UK/NZ)
Thanks Tony,
I’m on it but it’s quite complicated to find out the cause, unless to change the whole harness
I keep searching !!
Bertrand
Hi Kevin,
Thanks for these tips, I’ll let you know !
Bertrand
Thanks Frank,
I’ll do that this afternoon my time !
I’ll keep you all posted !
Bertrand