Starting electrical challenge - out of ideas

dylanirl · Feb 3, 2015

Hi Folks,

I am having a challenge with my series 3. I am not very experienced with older cars so please go easy on me.

I have a petrol 2.25 series III. It was running very well and then one day as the engine was idling it just died quite abruptly and has never started since.

When I try to start it the starting motor turns over nice and strongly. I have tested the battery and it is fine. There is petrol in the tank.

I have looked at the ignition system and replaced piece by piece...

Distributor
Rotor arm
leads
plugs
points
condensor
coil

Still nothing.

Some friendly folks have given me advice on working back from the plugs to see where there is a spark. I take the leads off the plugs and hold them closely to the engine... no spark. Take the king lead off the distributor and do the same... no spark.

Someone told me to eliminate the ignition switch run a cable from positive on battery to positive on coil... still nothing.

When I turn on the ignition I get 10.5 V between positive and negative on the coil.

Sorry for the long post but I am completely at a loss now as to where to go from here.

Any ideas??

Desperately,

Dylan

fv1620 · Feb 3, 2015

dylanirl said:
When I turn on the ignition I get 10.5 V between positive and negative on the coil.

Dylan, put your +ve prod of your voltmeter on the + terminal of the coil & -ve prod to earth.

With the ignition on you should get 12v or so all the time.

Now put the +ve prod on the - terminal of the coil & -ve prod to earth. With the points open you should read 12v or so as you did above. With the points closed it should read 0v, if it reads 0.5v or so you have high resistance at points due to arcing or dirt.

dylanirl · Feb 3, 2015

FV - Thanks so much for the response.

Put voltmeter on positive coil and earth and got 11v reading

Put on negative coil and earth and got .530 reading

Checked inside distributor like you suggested and found where the negative from coil goes to points had frayed a little and was touching inside of distributor casing.

Repaired.

Tested positive coil and earth and got bang on 12v

Tested negative coil and earth and got 12v

Turned engine and it started instantly!

You have brought my dead land rover (12 months lying there) back to life.

Thank you so much!

Rubins4 · Feb 3, 2015

fv1620 said:
Dylan, put your +ve prod of your voltmeter on the + terminal of the coil & -ve prod to earth.

With the ignition on you should get 12v or so all the time.

Now put the +ve prod on the - terminal of the coil & -ve prod to earth. With the points open you should read 12v or so as you did above. With the points closed it should read 0v, if it reads 0.5v or so you have high resistance at points due to arcing or dirt.

Excellent post and great knowledge.

That's why I'm on this forum. :thumbup:

fv1620 · Feb 3, 2015

Excellent result Dylan, thank you for letting me know.

Sometimes on forums I never get to hear the outcome & it all goes quiet that either means the problem is solved or the problem is not solved but the poster is even more disillusioned.

Anyway that gives us both satisfaction. I have a particular interest in military Land Rovers 24v screened systems & have been writing an article now for 5 years I think it is about 95 pages so far. It serialised in EMLRA Newsletter.

I look on here daily but usually don't feel I've got anything useful to say. But your post just caught my eye.

Anyway well done for fixing it.

dylanirl · Feb 4, 2015

and the story continues...

So I drove the beast out of the garage and left it running for a few minutes and it just died.

I checked everything and all appears to be fine except, like before, starting motor turns but no spark.

I checked the negative on the coil and earth and am getting 1.5V with points open and closed.

I have checked the points and inside the distributor housing and nothing is arcing or earthed incorrectly as far as I can tell.

I have a new set of points to pick up tomorrow because the points look worse for wear...

Any other suggestions? Completely at a loss.

Thanks folks!

fv1620 · Feb 4, 2015

dylanirl said:
I checked the negative on the coil and earth and am getting 1.5V with points open and closed.

Disconnect the coil lead at the distributor this should make your reading on - on coil go up to 12v. Short circuit the lead to chassis & that should go down to 0 volts. So that is simulating the action of the points.

If that works ok there must be shorting problem within the distributor. Unscrew & lift up the base plate & look underneath is there some sort bare metal linkage from the condenser to the insulated contact. Is this covered in detritus etc. Are you certain the points are assembled correctly with the insulating bushes?

fv1620 · Feb 5, 2015

The other thing to do is disconnect the CB lead to the distributor & connect it to your multimeter on the low Ohms range or buzzer & put the other lead to earth.

With the points open jiggle & fiddle with the base plate & lead to see if you can trigger a short or semi-short circuiting.

Also verify that when you rotate the shaft that the when the points close they do indeed produce a short circuit.

Don't worry about the role of the condenser too much in these tests. I have never seen a short circuiting condenser, leakage yes but shorting no. Anyway if it is about 1.5cm high it will be a metallized type that has self repair properties (although they can still leak) or if it is about 3cm long it is a paper/foil type that won't self heal but I doubt will be shorting even though the insulation can break down at higher voltages)

The only proper way way to test a condenser is not to use a multimeter as that only works at a few volts it needs to be tested on a Megger type tester using something like the sort of voltage it will work under around 300v. Yes high voltage is induced in the primary from only 12v. Any sparking at the points is 300v not 12v.

dylanirl · Feb 7, 2015

Hi

I tried removing the lead going to the points. I get 12v when I test from - on the coil and neg on the battery. If I short the wire from - on coil to the bodywork I get 0.8v when I measure from -coil to beg battery. It should be 0v right? Does this mean I have a short somewhere.

fv1620 · Feb 7, 2015

dylanirl said:
Hi

I tried removing the lead going to the points. I get 12v when I test from - on the coil and neg on the battery. If I short the wire from - on coil to the bodywork I get 0.8v when I measure from -coil to beg battery. It should be 0v right? Does this mean I have a short somewhere.

Dylan that's about right. 0.8v means there is a very low resistance of about 0.2 ohms between your earth point (on the engine?) & your battery negative terminal. If that is so then it could be significant voltage drop when drawing a lot of current when starting. So check the battery earthing strap & terminals to battery & earth strap to chassis. Similarly check the status of the engine chassis earth strap.

That may all be a red herring but needs following up anyway. Do the resistance / buzzer checks I outlined on the distributor.

dylanirl · Feb 7, 2015

Thanks!!

This had me frustrated almost to the point of tears today!

I did the resistance check. Hooked on to cable going from coil to points and other end to earth. With points closed I got a buzz. With points open... I got a buzz. Wriggled the cable a bit and buzz stopped. Found that where the cable attaches to the points had come loose again and must have been touching off the distributor casing. Fixed the cable and it started!

The part of the points that the cable connects on to has been damaged from metal fatigue due to connecting and disconnecting the cable. I need new points but it is all running now.

Thanks so much. Sorry if my question was basic but this situation has really given me a better understanding of how ignition systems in older cars work and it makes sense to me now.

Thanks again!

fv1620 · Feb 7, 2015

Dylan well done. Just think you have now become a seasoned expert on short circuiting problems in distributors & can now sort out someone else who gets the same problem at some stage.

You have learnt far more than reading a book about faults in ignition systems. These problems are a damn nuisance when they occur, the anger & tears are matched by the relief & warm satisfaction having diagnosed the problem accurately & attended to that.

Far better than arbitrarily picking on things to replace in acts of desperation.

"No treatment without a diagnosis"

Starting electrical challenge - out of ideas

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